Most Cited

Mechanical properties of sulfide glasses in all-solid-state batteries

Kato, Atsutaka; Nose, Masashi; Yamamoto, Mirai; Sakuda, Atsushi; Hayashi, Akitoshi; Tatsumisago, Masahiro

Effects of NH4Cl addition to perovskite CH3NH3PbI3 photovoltaic

Oku, Takeo; Ohishi, Yuya; Suzuki, Atsushi; Miyazawa, Yuzuru

Fabrication of composite positive electrode sheet with high active material content and effect of fabrication pressure for all-solid-state battery

Yamamoto, Mari; Takahashi, Masanari; Terauchi, Yoshihiro; Kobayashi, Yasuyuki; Ikeda, Shingo; Sakuda, Atsushi

Electrical and mechanical properties of glass and glass-ceramic electrolytes in the system Li3BO3-Li2SO4

Tatsumisago, Masahiro; Takano, Ryohei; Nose, Masashi; Nagao, Kenji; Kato, Atsutaka; Sakuda, Atsushi; Tadanaga, Kiyoharu; ...

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Feature: International Year of Glass
Full Paper
published : vol. 130, no. 8, August 2022
Madoka Ono, Kenji Shinozaki, Jumpei Ueda, Ryohei Oka, Tetsuo Kishi, Sunao Kurimura, Yoshihiro Takahashi, Tomoharu Hasegawa, Yoshimasa Matsushita, Takahiro Murata and Yoshiki Yamazaki
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As an anniversary event of International Year of Glass (IYOG), especially to help advertisement of IYOG in Japan, we devoted ourselves for half a year of making a glass poster, called “Ikka-ni Ichimai [the annual S&T (Science and Technology) poster for everyone, in Japanese]”. The title of the poster is “GLASS – The most universal modern material”, and is already distributed, by Japanese Ministry of Education, Culture, Sports, Science and Technology (MEXT), to all over Japan from elementary to high school, and even university. The distribution is done to promote their interests for science and technology. The final products, the poster, the corresponding webpage, and the movies to explain how to enjoy the poster, are very much welcomed by many people including kids and students who do not major in glass. The poster shows how glass has been evolved by humankind, and how it supported human life to develop. We are quite confident that people can understand, by looking through this poster, how inevitable glass is, in various fields; from culture and art, medicine, science, and technology. Our hopes are to evoke interests of children to glass and material science, which, in a long term, help continuous evolution of glass for the future which supports the humankind.
Feature: International Year of Glass
Review
published : vol. 130, no. 8, August 2022
Kyoko Yamahana
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Ancient Egyptian faience is a sintered quartz, usually with a blue-green glassy surface. Although its manufacturing method has been lost for about two thousand years, some descendants remained in the modern world, giving a clue to reconstructing the ancient technology. We now know that there are three distinct methods of faience making: efflorescence, cementation, and application. However, the study of faience has been mainly from the scientist’s point of view, not from the craftsman’s. This paper deals with replicating the ancient Egyptian faience from the creator’s viewpoint. The author proposes ways to manage the slumpy faience paste and improve its plasticity through experiments. Also, the experiments proved that the cementation method yields the best quality faience. The author also discovered that the surface glaze and bubbles differ in each method, and the difference can be observed by a low magnifying microscope. Such a handy means of examination will probably enlarge the possibility of examining valuable faience objects stored in museums. The outcome of the experiments tells that all three methods were present by the mid-Middle Kingdom Period, and the choice of a particular method might be based on the cost of manufacture.
Feature: International Year of Glass
Review
published : vol. 130, no. 8, August 2022
Tanguy Rouxel
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Glasses and crystals from the same chemical system mostly share the same interatomic bond strength. Nevertheless, they differ by the arrangement of bonds in space, which gives birth to different atomic packing efficiencies. We show in this review that as far as the elastic moduli and hardness are concerned, the atomic packing density predominates over the bond strength. The shear modulus of a glass is usually much smaller than the one of the crystallized polymorphs, thanks to a more efficient packing of atoms in the latter. In contrast, the increase in hardness is quite limited, likely because of the additional contribution of dislocation activity to the deformation processes beneath the indenter in the case of crystals (shear plasticity). We also show that the occurrence of chemical heterogeneities (weak channels) at the mesoscopic scale in glasses, which is often associated with the lack of long range atomic ordering, promotes easy fracture paths and is responsible for the low toughness and fracture surface energy.
Feature: International Year of Glass
Review
published : vol. 130, no. 8, August 2022
Shinji Kohara
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The advent of advanced quantum beam sources such as SPring-8 (synchrotron X-ray source) and J-PARC (spallation neutron source), which produce high-flux high-energy X-rays/neutrons, and advanced instrumentation techniques make it feasible to probe intermediate-range ordering in glasses and liquids. In particular, a combination of quantum-beam measurements and data-driven structure modelling assisted by advanced theory enables us to study both atomistic and electronic structures in glasses and liquids. In this article, recent state-of-the-art research studies on probing the order within disorder in oxide glasses and liquids are reviewed. Furthermore, the application of advanced topological analyses of glasses and liquids to uncovering the hidden ordering in the pairwise correlation is addressed.
Feature: International Year of Glass
Review
published : vol. 130, no. 8, August 2022
Tsuyoshi Honma, Kei Maeda, Shingo Nakane and Kenji Shinozaki
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Glass-ceramics have brought us necessary products for our modern society, such as heat-resistant tableware, biomaterials, electronics, photonics, and information technology. It has been more than 60 years since the invention of glass-ceramics, and even today, the research and development of characteristic glass-ceramics are ongoing. In particular, mechanical properties, thermal shock resistance, optical transparency, and ionic conductivity have always been important issues for glass researchers and the glass industry. This article reviews the fundamentals (materials and processes) and characteristic properties of modern glass-ceramics.
Feature: International Year of Glass
Review
published : vol. 130, no. 8, August 2022
Yusuke Daiko, Atsushi Sakuda, Tsuyoshi Honma and Akitoshi Hayashi
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Materials with high ionic conductivity are attracting a great deal of attention because they are indispensable for improving the performance of batteries, sensors, and capacitors. Solid electrolytes, in particular, have a potential to compensate for the shortcomings of liquid electrolytes, and are the subject of intense research and development worldwide. One of the big characteristics of glass is its high formability. Here we are focusing on glass-electrolytes. Differences between “superionic conductive glasses” and “ordinary glasses”, as well as the mixed alkali effect will be overviewed. In addition, glasses can retain large residual stress inside that can reach the order of several GPa depending on the cooling conditions. These residual stresses also affect ionic conductivity. Recent results on the application of glass formability and softening fluidity to the formation of interfaces in all-solid-state batteries, and to ion emission from sharpened glasses are reviewed.
Feature: International Year of Glass
Review
published : vol. 130, no. 8, August 2022
Madoka Ono and Junji Nishii
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Optical communication fibers are one of the most important inventions of the glass product industry. These fibers are the only product made of glass to which the Nobel prize has been awarded. As an anniversary review for the International Year of Glass, we examine the evolution of communication fiber materials including multicomponent glasses, which were expected to replace silica glass. Owing to the difficulties in manufacturing low-loss fibers, multicomponent glasses, except fluoride glass, were dropped as the candidates for the core material. Pure silica glass is currently used as the core material for long-haul optical communication. As research on loss-reduction seems to have been stagnant for almost 40 years, a new method on loss reduction using hot compression is welcomed. While summarizing the history of glasses investigated for optical fibers, expectations for breakthroughs are discussed.
Feature: International Year of Glass
Review
published : vol. 130, no. 8, August 2022
Atsunobu Masuno
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Over the last 20 years, many unconventional oxide glasses have been fabricated in bulk using a levitation technique. These glasses contain no or less network-former oxides; thus, they have been supposed not to vitrify so far. The levitation technique could vitrify them because the levitated melt was maintained without touching anything; thus, crystal nucleation was extremely suppressed. This review presents a brief introduction to the levitation technique. It also summarizes some functionalities that emerged in the glasses prepared using this technique, such as high refractive index, infrared transparency, strong luminescence, large magneto-optical effect, high elastic moduli, and crack resistance.
Feature: International Year of Glass
Review
published : vol. 130, no. 8, August 2022
Koichi Kajihara, Kazuyoshi Kanamori and Atsushi Shimojima
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Sol–gel process is defined by IUPAC as “process through which a network is formed from solution by a progressive change of liquid precursor into a sol, to a gel, and in most cases finally to a dry network”. Among the many recent topics on sol–gel processing, the synthesis and applications of nonporous glasses and ceramics, aerogels, and mesoporous and/or nanostructured materials are briefly reviewed in terms of reaction mechanisms, process optimization, and functionalities.
Feature: International Year of Glass
Review
published : vol. 130, no. 8, August 2022
Kohei Kadono and Naoyuki Kitamura
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Chalcogenide glass is a unique material applicable to infrared-transmitting optical elements that cover the atmospheric windows. It can be manufactured using molding technology, which provides mass productivity and high quality. Interest in chalcogenide glass research and developments has increased recently because of the rapid growth of the infrared optics market. This review summarizes the glass formation and properties of recently developed chalcogenide glasses. Selenium-based glasses which are widely used commercially have been introduced in comparison with infrared-transmitting crystals such as Ge and ZnSe. For sulfur-based glasses, glass-forming systems based on Ge–S and Ga–S have been described. These systems are completely free of arsenic and selenium, which are commonly used in conventional chalcogenide glasses. However, they provide glasses that are thermally stable against crystallization, and moldable. The typical spectral windows for Ge–S and Ga–S-based glasses have ranges of approximately 0.6–11 and 0.8–13 µm, respectively, although the short wavelength side strongly depends on the composition. Tellurium-based glasses are characterized by transmission in the far-infrared region, beyond 20 µm, and a refractive index higher than three. Recent studies on the temperature dependence of the viscosity and viscoelastic behaviors of chalcogenide glasses, which are both important for precision molding technology, are also discussed. Two characteristic structural relaxations have been observed in sulfide and selenide glasses.
Feature: International Year of Glass
Review
published : vol. 130, no. 8, August 2022
Kohei Soga
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The three research themes, fiber optics, upconversion, and biophotonics seem to be unconnected, but they can be actually connected. The author studied glass science in a glass laboratory when he was a student, and is currently conducting research on biophotonics using near-infrared light. This paper introduces the development of applications in different fields connected by basic science, starting from glass science and goaling to biophotonics.
Feature: International Year of Glass
Review
published : vol. 130, no. 8, August 2022
Akiko Obata, Sungho Lee and Toshihiro Kasuga
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The development of bioactive glasses, which began with the Hench’s invention of Bioglass®, has considerably advanced over the past 20 years toward the creation of materials that not only chemically bond to living tissue, but also promote tissue regeneration. Some inorganic ions have the effect of stimulating cells and promoting biological functions, including bone formation. Glass-based materials have a significant advantage in the controlled release of inorganic ions because their compositions can be chosen systematically. Stimulating cells and improving therapeutic effects via the inclusion of various inorganic ions released from bioactive glass may represent a key strategy in the development of advanced biomaterials. This paper briefly reviews the research work related to bioactive glasses designed for tissue regeneration undertaken in the past two decades.
Feature: International Year of Glass
Special Article
published : vol. 130, no. 8, August 2022
Tokuro Nanba, Yasuhiko Benino and Tomoko Akai
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In general, glass has been recognized as an environmentally friendly material. However, the production of glass requires a lot of heat energy, and the raw materials also emit CO2 at the melting process. In fact, commercial glasses are not easy to recycle. In glass industry of Japan, various efforts have been made so far to reduce the environmental impact of glass. In this paper, not only glass manufacturing technologies but also glass recycling technologies were reviewed, and the future glass production technologies to achieve carbon neutrality were also introduced.
The 76th CerSJ Awards for Academic Achievements in Ceramic Science and Technology: Review
Special Article
published : vol. 130, no. 8, August 2022
Hiroshi Irie
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The author and coworkers focused on the fabrication of composite photocatalysts and charge transfer between composite constituents for increased activity and sensitivity to visible light, aiming at developing materials for environmental preservation through the oxidative decomposition of organic pollutants and clean energy production through water splitting for hydrogen generation. Cu2+ ion-grafted titanium dioxide (TiO2) was designed on the basis of visible-light-induced interfacial charge transfer from the valence band (VB) of TiO2 to Cu2+, generating high oxidative decomposition activity owing to the utilization of photogenerated holes in the VB of TiO2. Cu+ produced by electron injection was converted back to Cu2+ by oxygen (O2) reduction through multi-electron O2 reduction reaction. As for water splitting, zinc rhodium oxide (ZnRh2O4) and bismuth vanadate (Bi4V2O11) as H2 and O2 evolution photocatalysts, respectively, were connected with silver (Ag), acting as a solid-state electron mediator, to prepare a composite photocatalyst that is sensitive to red light. The key function of the heterojunction photocatalyst is the transfer of photoexcited electrons from the conduction band (CB) of Bi4V2O11 to the VB of ZnRh2O4 via Ag. Thus, the photoexcited electrons in the CB of ZnRh2O4 and the holes in the VB of Bi4V2O11 effectively reduced and oxidized water, respectively, thereby splitting water and liberating H2 and O2 at a stoichiometric ratio.
The 76th CerSJ Awards for Advancements in Ceramic Science and Technology: Review
Special Article
published : vol. 130, no. 8, August 2022
Takahisa Shiraishi, Akinori Tateyama, Hiroshi Uchida and Hiroshi Funakubo
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Epitaxial films of (K,Na,Li)NbO3 with 10 µm thickness and various Li contents were fabricated at 240 °C on (001)La:SrTiO3 substrates by a hydrothermal method, and their crystal structures and piezoelectric properties were investigated. The film thickness was controlled by varying the deposition time (up to 3.5 h) and the number of deposition cycles. Scanning electron microscopy observations showed that dense thick films were formed. X-ray diffraction (XRD) measurements showed that {001}c-oriented epitaxial films were deposited, and the out-of-plane lattice constant changed with an increase in the nominal composition A = [LiOH]/([KOH] + [NaOH] + [LiOH]) of the alkaline source solution. High-temperature XRD measurement revealed that with an increase in A, the Curie temperature increased, while the orthorhombic–tetragonal phase transition temperature decreased from 210 to 120 °C. These structural changes indicate that the Li content in the thick films can be controlled by varying A. The dielectric properties depend on the measurement frequency, and the minimum relative dielectric permittivity at all frequencies was observed at A = 0.02. Curves of field-induced strain vs. electric field showed that the maximum normalized strain of Smax/Emax = 40 pm/V was observed at A = 0.03, indicating that Li substitution is an effective way to improve the piezoelectricity of the hydrothermally deposited (K,Na)NbO3 thick films. Interestingly, all thick films exhibited a piezoelectric response despite the applied electric field being lower than the coercive field. Moreover, the Smax/Emax value did not change significantly with an increasing applied electric field. These results suggest that the hydrothermally deposited (K,Na,Li)NbO3 thick films adopt a self-polarized state without poling treatment.
The 75th CerSJ Awards for Advancements in Ceramic Science and Technology: Review
Special Article
published : vol. 130, no. 8, August 2022
Yohei Onodera
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Understanding the structure of disordered materials is still one of the most challenging topics in materials science because of insufficient structural information on experimental data. In this article, recent studies in solving the structure of glassy oxide materials via a combination of quantum beam experiments and computer simulations with the aid of advanced topological analyses are reviewed. To investigate glass structure on the intermediate length scale, three-dimensional atomistic structure models, which reproduce the multiple experimental dataset, were constructed. Furthermore, various topological analyses found that the network topology is an important structural feature for understanding properties of oxide glasses. The comprehensive approach including experimental, computational, and analytical method will be a promising way to probe the hidden order in disordered structure and provide crucial knowledge to design new glass materials with novel characteristics.
The 76th CerSJ Awards for Advancements in Ceramic Science and Technology: Review
Special Article
published : vol. 130, no. 8, August 2022
Yuki Sugiura
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As the population ages worldwide, the importance of maintaining the metabolism of the skeletal system becomes increasingly important. The skeleton is the core of the locomotor and oral structure. Moreover, infection control is an essential part of orthopedic and oral surgery. This paper investigates new bone substitutes fabricated by the ionic substitution method leading to octacalcium phosphate (OCP) with excellent contact antibacterial ability, biocompatibility, and bone replacement. To improve the functionality of OCP-based materials as a bone substitute, we introduce a novel OCP block fabrication method based on the dissolution–precipitation method, study the factors that induce OCP in solution, and propose a robust method for cation substitution in the OCP unit lattice named the ionic insertion method. We then fabricate Ag-substituted OCP (OCP–Ag) blocks using this method and evaluate their antibacterial activity in vivo. These techniques will contribute to new-generation medical services and improve the quality of life of individuals requiring implants.
Full Paper
published : vol. 130, no. 8, August 2022
Fangcheng Cao, Zhen He and Lixia Yang
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The oxidation performance of silicon carbide (SiC) coating on nuclear fuel particle and the subsequent effect on the mechanical integrity was investigated. The effects of steam content on the phase composition and microstructure of the SiC layer at different temperatures were discussed. Reaction rates of steam with the SiC layer were found to obey the liner-parabolic oxidation law. The fracture strength of SiC shell was evaluated, which was dominated by the thickness variation of the SiC. Furthermore, finite element analysis was performed to simulate the stress distribution in the SiC shell during the crush test. The results revealed the SiC shell of reduced thickness caused by oxidation had higher stress concentration at the inner surface and resulted in a lower fracture strength value.
Full Paper
published : vol. 130, no. 8, August 2022
Yuki Makinose
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This paper discusses the hydrothermal synthesis of monodisperse oleate-capped iron oxide nanoparticles from an ammonia-treated Fe-oleate precursor solution. Nanoparticle samples synthesized at different temperatures were characterized using a combination of X-ray diffraction, Fourier-transform infrared spectroscopy, transmission electron microscopy, dynamic light scattering, vibrating sample magnetometry, and thermogravimetry-differential thermal analysis. This characterization revealed nanoparticles comprising inverse-spinel-type crystals covered by an oleate double-layer, with the saturation magnetization of the nanoparticles increasing with the temperature used for hydrothermal synthesis. Near-monodisperse nanoparticle distributions were obtained with hydrothermal reactions conducted at 150 °C.
Full Paper
published : vol. 130, no. 8, August 2022
Yoshiko Higashi and Eiichi Koga
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Effect of thermal radiation on reliability is investigated for ZnO-based multilayer ceramic varistors (MLCVs). Withstanding capabilities against load dump surge (LDS) are compared between MLCVs with connecting structure of various-sized chips (co-MLCVs) and large size ones (5.7 × 5.0 × 3.0 mm). The LDS stability are improved with surface area of co-MLCVs. In particular, when connected chips are under 3.2 × 2.5 × 1.6 mm in size, co-MLCVs have more 30 % higher withstanding voltage (>100 V) and current (>53 A) than those of conventional large MLCVs, despite the same electrode area and nonlinear VI characteristics. The results of thermal simulations show that heat dissipation in co-MLCVs is improved due to an expansion in surface area with a decrease of chip size. Thus, this notable enhancement of stability should be caused by an increase of heat radiation. And more, the LDS capability is independent of variation coefficient in V1mA of chips (e.g., as σ/x < 0.032). It is evident that improvement of radiation performance gives a significant increase in reliability of MLCVs. The high thermal radiation certainly leads to further advance in MLCVs for high-energy surge.
Full Paper
published : vol. 130, no. 8, August 2022
Takehiro Koike, Takumi Nishikubo, Yuki Sakai, Hirofumi Ishii and Masaki Azuma
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Negative thermal expansion (NTE) in Bi0.5+xNa0.5−xVO3 is investigated. The parent compound, Bi0.5Na0.5VO3, is a lead-free polar perovskite oxide with a tetragonal distortion comparable to that of ferroelectric PbTiO3 owing to the ordering of dxy orbital of V4+ with d1 electronic configuration. The c/a ratio was decreased by electron doping to V4+ through increasing Bi3+/Na+ ratio and transition to a non-polar cubic phase on heating accompanied by NTE with a large volume shrinkage of −2.28 % was enabled. It is found that the Bi0.5Na0.5VO3 derivatives exhibit NTE when the c/a ratio is smaller than the critical value of ∼1.06.
Full Paper
published : vol. 130, no. 8, August 2022
Lei Liu and Kenji Shinozaki
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In this study, we investigated the incorporation of 2D transition metal carbides and nitrides (MXenes) in glass materials. Ti3C2 MXene was successfully incorporated into borosilicate glass by spark plasma sintering. The addition of 1 vol % MXene nanoplatelets to the borosilicate glass resulted in them being homogenously distributed in the glass matrix. The addition of 2 vol % MXene nanoplatelets, however resulted in a coarser distribution. The fracture toughness of the glass samples with 0, 1 and 2 vol % MXene were 0.94, 1.36, and 1.21 MPa m1/2, respectively. The enhanced fracture toughness of borosilicate glass with Ti3C2 MXene is ascribed to crack deflection, crack bridging, and pull-out of Ti3C2 MXene.
Full Paper
published : vol. 130, no. 8, August 2022
Kenji Oda
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One dimensional heat transport model is formulated to solve melting rate of batch as well as unsteady temperature distribution in thickness direction of batch. Heat exchange of batch with decomposed gas, volumetric change of batch during melting and tide of foam are considered. Numerical simulation is performed to demonstrate the temperature distribution during both heating and melting period. The simulation also presents steady melting rate for foam thickness and response of the rate for tide of foam. The calculated result provides time-temperature history to estimate reaction path of batch and characteristics of rough melt.
Full Paper
published : vol. 130, no. 8, August 2022
Miki Uchida, Takahiro Takei, Nobuhiro Kumada, Hideyuki Tsutsui, Kazuki Azuma and Takashi Toyama
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AlN was succeeded to be synthesized at a low temperature of 900–1000 °C from the anhydrous aluminum chloride-melamine complex of a ratio of 1 to 3. To synthesize AlN at low temperature, four complexes were made from the anhydrous aluminum chloride with melamine, urea, hexamethylenetetramine, and aniline as ligands. The coordination state of the complex was confirmed by Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS). For the Al2p XPS spectra, a peak with higher binding energy emerged in the complex with melamine than the other complexes. For the N1s XPS spectra, the main peak with higher binding energy also can be detected, which indicates coordinated N to the Al atom. Consequently, the complex of AlCl3 and three equivalents melamine showed a better coordination state than the others by FT-IR and XPS spectra. X-ray diffraction (XRD) patterns confirmed that the AlN phase forms for AlCl3-equivalent melamine, -three equivalents melamine, and -three equivalents urea complex by heating at a low temperature of 900 and 1000 °C. Especially AlCl3-three equivalents melamine complex can be converted to the AlN with relatively high crystallinity and fewer impurities due to its strong Al–N bonding on the triazine ring. The excess melamine due to the three equivalent amounts may work as reserve one which can provide to prevent a lack of melamine at high temperatures during AlN formation.
Full Paper
published : vol. 130, no. 8, August 2022
Hiroyuki Yamaura, Emiri Tajima, Maiko Nishibori, Syuhei Yamaguchi, Kengo Shimanoe and Hidenori Yahiro
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The tin–metal mixed hydroxides CaSn(OH)6, MnSn(OH)6, CoSn(OH)6, and ZnSn(OH)6, with cubic morphologies, were prepared using a coprecipitation method; they were subsequently transformed into the corresponding tin–metal mixed oxides by calcination at 600–900 °C. The crystalline structures and the morphologies of the various samples at each calcination step (just prepared, dried at 110 °C, and calcined at 600 and 900 °C) were systematically evaluated by X-ray diffractometry, scanning electron microscopy, transmission electron microscopy, and X-ray absorption fine structure analyses. The cubic shapes of the CaSn(OH)6 and ZnSn(OH)6 nanoparticles were maintained after calcination of them at 600 and 900 °C, while those of MnSn(OH)6 and CoSn(OH)6 ones were not maintained after calcination of them.
Full Paper
published : vol. 130, no. 8, August 2022
Yuki Nakashima, Manabu Fukushima, You Zhou and Hideki Hyuga
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Grinding is an important and widely applied industrial process for decreasing the size of particles, and it has been most frequently carried out together with liquid medium to improve the efficiency. In this study, the relationship among various grinding times of SiO2 particles by rotating ball milling, volumes of ethanol used as the medium (corresponding to pendular to slurry states) and types of the liquid medium were systematically investigated in terms of the grinding efficiency. Without ethanol, the SiO2 particles could never be pulverized even after 48 h of the ball milling, whereas they were pulverized in its presence because the ethanol adsorbed on the particle restricted their adhesion. The highest grinding efficiency was achieved with 1 ml of ethanol against 20 g of SiO2 particles with polypropylene vessel including 200 g of zirconia balls with a diameter of 5 mm and seven zirconia balls with a diameter of 10 mm under 150 rpm for 24 h. The grinding efficiency increased with decreasing viscosity, because the impact power generated by the milling was efficiently conducted toward the particles due to its high flowability and low concentration in the impact zone. The ratio of the dipole moment to molecular volume in the liquid medium strongly affected the grinding efficiency, in which ethanol could efficiently serve as the medium, because they could easily adsorb to the SiO2 particle. The overall grinding mechanism and process factors were investigated.
Technical Report
published : vol. 130, no. 8, August 2022
Susumu Nakayama
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In the present study, simultaneous gross immobilization of radioactive Cs and Sr in zirconium phosphate was investigated by two methods. In the “dry method,” a mixture of HZr2(PO4)3 with varying amounts of CsNO3 and Sr(NO3)2 was heat-treated at 700 °C for 5 h to prepare Cs + Sr immobilized samples. At Cs + Sr immobilization of 0.3 + 0.15, the leaching amounts of Cs and Sr in 1 mol·dm−3 of HCl solution treated at 160 °C for 24 h were 2.9 × 10−4 g·m−2 and 3.9 × 10−4 g·m−2, respectively. In the “autoclave method,” aqueous solutions containing 0.5 and 0.25 mol of CsNO3 and Sr(NO3)2, respectively, against 1 mol of (H3O)Zr2(PO4)3 were thermal-treated at 150–250 °C for 24 h to prepare Cs + Sr immobilized samples; immobilization of Cs and Sr was observed at 150 °C. The immobilized amount of Cs and Sr increased as the treated temperature increased, while the leaching amounts of Cs and Sr in 1 mol·dm−3 of HCl solution treated at 160 °C for 24 h decreased. The amount of immobilized Cs and Sr on (H3O)Zr2(PO4)3 at 250 °C were 0.30 and 0.20, and leaching amounts of Cs and Sr were 1.0 × 10−3 g·m−2 and 1.4 × 10−3 g·m−2, respectively.
Note
published : vol. 130, no. 8, August 2022
Naoya Terada, Tomoya Arimoto, Kazuhiko Hara, Masaru Sakai and Tetsuya Kouno
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ZnO nano- and microwires were grown on Si(111) substrates by mist chemical vapor deposition (mist-CVD). In 30 min of crystal growth, ZnO nanowires of approximately 100–500 nm diameters and 800–1000 nm length were grown. In 4 h of crystal growth, ZnO microwires were grown with some of them having a diameter and length of more than 2 and 9 µm, respectively. ZnO crystals grown for 30 min and for 4 h exhibited clear room-temperature photoluminescence (RT-PL) peaks near the band gap energy. Under high-optically pumped conditions, some ZnO microwires exhibited sharp peaks in RT-PL spectra, indicating that optically pumped lasing actions were obtained based on optical microcavities formed in a ZnO microwire.
Review
published : vol. 130, no. 8, August 2022
Katsuyuki Matsunaga, Masato Yoshiya, Naoya Shibata, Hiromichi Ohta and Teruyasu Mizoguchi
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Point defects, dislocations, grain boundaries and interfaces are always involved in ceramic microstructures and play important roles for physical and chemical properties of ceramics. Currently, proper control of these crystal defects is inevitable to tailor ceramic materials with superior properties. This article reviews recent research projects on distinct properties and phenomena in ceramics due to crystal defects. In particular, we would like to emphasize importance of central core regions of crystal defects, namely, “crystal defect cores”. They have specific electronic and atomic structures that are different from those in bulk. Recent advances of nanoscale characterizations and theoretical calculations make it possible to acquire a variety of quantitative data on electronic structures enclosed at the crystal-defect cores, which gives clear understanding of various ceramic properties at the electronic and atomic levels.
Feature: Cutting edge research on electroceramics, 2021
Review
published : vol. 130, no. 7, July 2022
Sayuri Okunaka, Yugo Miseki and Kazuhiro Sayama
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Photoelectrochemical (PEC) production of H2 from saltwater over a semiconductor photoelectrode under solar-light irradiation is one of the effective technologies for developing a cost-effective sustainable energy conversion process. However, because saltwater such as seawater contains Cl, O2 and HClO are produced competitively during oxidation reactions by photogenerated holes from electrolytes containing Cl during the photo-electrolysis reaction. HClO is a high value-added chemical used for bleaching, etc., however, it is also an undesirable chemical that accelerates corrosion deterioration of large-scale water splitting systems. Therefore, it is necessary to control selectivity of oxidative O2/HClO production in electrolytes containing Cl over photoelectrodes. In this review, we summarized our recent innovations in selective O2 or HClO production over the visible-light driven BiVO4/WO3 photoanodes by simple modification of metal oxides. Modifications of metal oxides such as MnOx or CoOx via spin-coating onto a photoelectrode could control the selectivity on the O2/HClO production from an aqueous solution containing Cl effectively. In addition, controlling loading conditions such as the loading amount of metal oxides, and calcination temperatures after coating a metal precursor solution enabled us to prepare photoelectrodes that produce O2 or HClO with selectivity of almost 100 % using MnOx or CoOx, respectively, along with maintaining their PEC performance under solar-light irradiation.
Feature: Cutting edge research on electroceramics, 2021
Full Paper
published : vol. 130, no. 7, July 2022
Ryusei Ogawa, Shinobu Fujihara and Manabu Hagiwara
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The effects of dual doping by trivalent and monovalent cations on the thermoelectric properties of CaMnO3−δ ceramics were investigated. Na+ was selected as the monovalent cation, while three rare-earth (R) trivalent cations of La3+, Gd3+, and Dy3+ were used to study the role of their size and mass in the electrical and thermal transport properties. Dense ceramic samples with a nominal composition Ca1−x(R1/2Na1/2)xMnO3 (x = 0.1, 0.2, and 0.3) were fabricated via the conventional solid-state reaction route. Due to the partial evaporation of Na during sintering, the electrical conductivity increased and the Seebeck coefficient decreased with the doping level. Additionally, the dual doping by Na and R ions effectively decreased the thermal conductivity. The comparison of the thermoelectric properties of the samples demonstrated that a smaller and heavier R ion is more effective to obtain a high thermoelectric power factor and a low thermal conductivity. As a result, the sample with R = Dy and x = 0.1 possessed a high dimensionless figure-of-merit (ZT) of 0.11 at 1000 K.
Feature: Cutting edge research on electroceramics, 2021
Full Paper
published : vol. 130, no. 7, July 2022
Yukio Suga, Sou Yasuhara, Takaaki Tsurumi and Takuya Hoshina
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The ferroelectric properties of AgxK1−xNbSi2O7 (x = 0–0.10) single crystals were evaluated to understand the effect of Ag substitution on ferroelectricity in KNbSi2O7. Millimeter-sized plate-like AgxK1−xNbSi2O7 single crystals were fabricated by crystallization of the glass phase. The remanent polarization of AgxK1−xNbSi2O7 decreased with increasing the amount of Ag, meaning that the ferroelectricity of KNbSi2O7 is reduced by Ag substitution. Such a tendency was also confirmed by first-principles calculations for KNbSi2O7 and AgNbSi2O7. The displacement of Nb from the center of gravity of the NbO6 octahedron and the rotation of the NbO6 octahedron around the c-axis were smaller in AgNbSi2O7 than in KNbSi2O7. These may be due to the larger electronegativity and smaller ionic radius of Ag. The similarities between the AgxK1−xNbSi2O7 and AgxK1−xNbO3 were also discussed.
Feature: Cutting edge research on electroceramics, 2021
Full Paper
published : vol. 130, no. 7, July 2022
Ken Watanabe, Ayumu Tashiro, Yoshihiro Ichinose, Shinichi Takeno, Koichi Suematsu, Kazutaka Mitsuishi and Kengo Shimanoe
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Li7La3Zr2O12 (LLZ) has great potential as a solid electrolyte for co-fired all-solid-state Li-ion secondary batteries. However, to realise a solid-state battery using LLZ, the sintering temperature of LLZ should be reduced to one that can suppress the formation of a high-resistance reaction layer at the interface between LLZ and the electrode. In this study, we demonstrate an effective method for reducing the sintering temperature of Li6La3ZrTaO12 by combining partial Bi-substitution for Ta and precise control of the compositional deviation. The intentional tuning of the La deficiency in Li6La3ZrTa0.8Bi0.2O12 (LLZTB0.2) promoted the formation of a liquid phase based on Li2O–Bi2O3 at the grain boundary, resulting in its densification at 775 °C. Furthermore, we fabricated a co-fired all-solid-state half-cell based on an LLZTB0.2 electrolyte attached to a LiCoO2 + LLZTB0.2 composite electrode and a half-cell operated at 60 °C. From these results, it was found that the proposed concept is effective in reducing the sintering temperature of LLZ and is applicable for co-firing an all-solid-state battery.
Feature: Cutting edge research on electroceramics, 2021
Full Paper
published : vol. 130, no. 7, July 2022
Yuji Sakurai, Xueyou Yuan, Shinya Kondo, Masahito Yoshino, Takanori Nagasaki and Tomoaki Yamada
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Deposition condition of (001)-epitaxial K(Ta0.6Nb0.4)O3 (KTN) films on SrRuO3/SrTiO3 substrates by pulsed laser deposition was optimized. The optimized KTN film showed a saturated ferroelectric hysteresis loop with large withstand electric field, and the paraelectric to ferroelectric phase transition at room temperature (RT). Electro-optic (EO) property was characterized by modulation ellipsometry at RT, showing the maximum EO coefficient rc of 42 pm/V, which is larger than the previously reported value for KTN thin films having the same composition. Our findings show the importance of the precise tuning of deposition condition to achieve the large EO response in KTN films, promoting the potential application as a light modulator in EO devices at ambient temperature in the future.
Feature: Cutting edge research on electroceramics, 2021
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published : vol. 130, no. 7, July 2022
Tsukasa Katayama, Akira Chikamatsu and Tetsuya Hasegawa
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Double-perovskite GdBaCo2O5.5 epitaxial films were fabricated on SrTiO3(001) substrates. X-ray diffraction and scanning transmission electron microscopy measurements of a 37 nm thick film confirmed the ionic order of Gd and Ba along the out-of-plane direction. The Gd/Ba order was absent within the region 1 nm from the film/substrate interface owing to the migration of Sr ions from the substrate. Unlike the 37 nm thick film, a thin film with a thickness of 10 nm did not show a distinct antiferromagnetic to ferromagnetic (FM) transition, whereas large magnetization was observed at low temperature. This was proposed to be because the cation-disordered phase near the interface was FM, even at low temperatures.
Feature: Cutting edge research on electroceramics, 2021
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published : vol. 130, no. 7, July 2022
Takanori Mimura, Takao Shimizu and Hiroshi Funakubo
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Y-doped TaON films were grown on (001)YSZ and (012)Al2O3 substrates by radio frequency (RF) magnetron reactive sputtering deposition from Ta metal target and Y metal chips under the mixture gases of N2, O2 and Ar gases. Films with various Y content were prepared by changing area ratio of Y/(Y + Ta) of the target. The pure monoclinic phase was obtained for TaON films on both substrates by controlling the partial pressure of N2 and O2 gasses. Crystal structure changed from the monoclinic phase to the orthorhombic one with the lattice parameters of a = 0.518 nm, b = 0.488 nm, and c = 0.504 nm with the increase in Y content in the films. Our results reveal that TaON could be used as a novel mother fluorite-like monoclinic structure to prepare orthorhombic phase.
Feature: Cutting edge research on electroceramics, 2021
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published : vol. 130, no. 7, July 2022
Shinnosuke Yasuoka, Ryoichi Mizutani, Reika Ota, Takahisa Shiraishi, Takao Shimizu, Shintaro Yasui, Yoshitaka Ehara, Ken Nishida, Masato Uehara, Hiroshi Yamada, Morito Akiyama, Yasuhiko Imai, Osami Sakata and Hiroshi Funakubo
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The thickness dependences of crystal structures and ferroelectric properties were investigated for (Al0.8Sc0.2)N films with thicknesses of 12 to 130 nm deposited on (111)Pt/TiOx/SiO2/(100)Si substrates. The internal structural parameter u, representing the crystal anisotropy of the wurtzite structure, decreased with decreasing film thickness. This was attributable mainly to the in-plane compressive strain originating from the larger atomic distance of (Al0.8Sc0.2)N film compared to that of the underlying Pt layer. Well-saturated Pr values were obtained at room temperature for the films down to 20 nm in thickness. The Pr value of the 12-nm-thick film tended to saturate against the electric field when the measurement temperature increased to 150 °C. These Pr values are considerably higher than those of conventional ferroelectric materials such as Pb(Zr,Ti)O3 and HfO2-based films in the thickness region below 20 nm. The Pr value tended to increase for film thicknesses below 50 nm. This originated from the increase in crystal anisotropy with decreasing film thickness due to the strain from the underlying Pt layers. Moreover, the significantly large Pr values of these strained films were larger than the expected values of pure AlN and were in good agreement with the theoretically calculated predictions based on the crystal anisotropy, u parameter. This suggests that the Pr values of (Al,Sc)N can be controlled mainly by the u parameter.
Feature: Cutting edge research on electroceramics, 2021
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published : vol. 130, no. 7, July 2022
Yuichi Sakuda, James R. Hester and Masatomo Yashima
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Oxide-ion conductors based on hexagonal perovskite-related oxide Ba7Nb4MoO20 have attracted much attention due to high oxide-ion and proton conductivities and potential applications in many electrochemical devices such as solid oxide fuel cells (SOFCs). Herein, we report simultaneous improvement of oxide-ion conductivity and suppression of proton conductivity by Cr6+ doping in Ba7Nb4MoO20. New materials Ba7Nb4−xCrxMoO20+x/2 (x = 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5) were synthesized. It was found that Ba7Nb3.8Cr0.2MoO20.1−δ (δ is the amount of oxygen deficiency in Ba7Nb3.8Cr0.2MoO20.1−δ) exhibits high oxide-ion conductivity of 1.6 × 10−3 S cm−1 at 508 °C and 1.1 × 10−2 S cm−1 at 904 °C in static air and low proton transport number under wet conditions. Ba7Nb3.8Cr0.2MoO20.1−δ also shows wide electrolyte domain in the oxygen partial pressure P(O2) regions from 1 to 2.2 × 10−27 atm (304 °C) and 1 to 1.5 × 10−26 atm (604 °C), indicating extremely high chemical and electrical stability. The structure analyses have shown that Ba7Nb3.8Cr0.2MoO20.1−δ is a hexagonal perovskite related oxide at 22 and 800 °C. The refined crystal structure of Ba7Nb3.8Cr0.2MoO20.1−δ has oxygen-deficient cubic (c′) close-packed Ba(O1)2−y(O5)z layer where y is the amount of oxygen vacancy at the tetrahedral O1 site and z is the amount of interstitial octahedral oxygen at the O5 site. The Cr bond valence sum indicates an oxidation number of +6: Cr6+. The Cr6+ cation is located at a crystallographic site near the c′ layer, which leads to the excess oxygen and high conductivity, and is likely to suppress the proton conduction. Maximum-entropy method (MEM) analyses have demonstrated that oxide ions two-dimensionally migrate through the lattice O1 and interstitial O5 sites in the c′ layer via the interstitialcy diffusion mechanism at 800 °C, which enables the high oxide-ion conduction. Cr6+ doping in various hexagonal perovskite-related oxides would be a new strategy for the simultaneous improvement of oxide-ion conductivity and suppression of proton conduction.
Feature: Cutting edge research on electroceramics, 2021
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published : vol. 130, no. 7, July 2022
Naohiro Tomiyama, Sou Yasuhara, Takaaki Tsurumi and Takuya Hoshina
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An oxide solid electrolyte with high Li-ion conductivity is in strong demand to improve the safety of all-solid-state Li-ion batteries. However, only a limited number of crystal structures have been reported as solid electrolytes due to the difficulty of exploring superior solid electrolytes. In this study, we focused on a corundum-related structure of a LiNbO3-type one in LiNbO3 because a corundum-type structure was previously reported as an anode material. A LiNbO3–Al2O3 system was synthesized via a conventional solid-state reaction, and its crystal structure and ionic conductivities were evaluated. The substitution of Al2O3 into LiNbO3 was revealed by X-ray diffraction results, and the substitution limit of Al2O3 was 40 mol % to LiNbO3. AC impedance measurements showed an enhancement of ionic conductivity of LiNbO3, with 1.5 × 10−5 S/cm as the highest value.
Feature: Cutting edge research on electroceramics, 2021
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published : vol. 130, no. 7, July 2022
Kota Hasegawa, Takao Shimizu and Naoki Ohashi
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The density functional theory (DFT) was employed to understand the ferroelectric behaviors of wurtzite (WZ)-type aluminum nitride (AlN). To explain the decrease in the coercive field (Ec) due to lattice deformation, the total energy and enthalpy of the strained WZ phase were compared to those of the non-polar (NP) phase, which acted as a transition state during polarity switching. The shrinkage of the c-axis length and elongation of the a-axis length were favorable for reducing Ec. In addition, the calculated residual stress in the transient NP phase was as high as 30 GPa, suggesting that such a high residual stress may be related to the polarity switching behavior under a very high electric field.
Feature: Cutting edge research on electroceramics, 2021
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published : vol. 130, no. 7, July 2022
Mizuki Watanabe, Honoka Takahashi, Kazuyoshi Uematsu, Mineo Sato, Takaki Masaki, Dae-Ho Yoon and Kenji Toda
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All-inorganic halides exhibit excellent optical as well as luminescence properties. Among them, non-toxic copper-doped halide Cs2ZnCl4 with high stability is a promising material. However, the conventional method for preparing these materials, using the hot injection technique, is unsuitable for mass production. Therefore, herein, we suggest a simple and low-temperature (below 100 °C) method without using special equipment, regents, and treatments. Cu-doped Cs2ZnCl4 was successfully synthesized using the water-assisted solid-state reaction (WASSR) method, and the oxidation state of Cu in the samples was estimated through the iodometric titration technique. The optical and luminescence properties were investigated using the absorption and photoluminescence excitation/emission spectra. Significantly, Cu-doped Cs2ZnCl4 exhibited unique green emission centered at ∼520 nm under ultraviolet irradiation. Moreover, the oxidation of Cu in the Cs2ZnCl4 lattice was suppressed owing to the low-temperature conditions in the WASSR.
Feature: Cutting edge research on electroceramics, 2021
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published : vol. 130, no. 7, July 2022
Haruki Zayasu, Takahiko Kawaguchi, Hiroki Nakane, Nobuyoshi Koshida, Kazuo Shinozaki, Hisao Suzuki, Naonori Sakamoto and Naoki Wakiya
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Epitaxial growth of yttria-stabilized zirconia (YSZ) thin film on through-hole-type porous silicon [tht-PSi(001)] with vertical pores penetrating from the surface to the back side of the Si(001) substrate was achieved. The in-plane and out-of-plane lattice parameters of YSZ thin film deposited on the tht-PSi(001) were, respectively 0.5167 and 0.5124 nm. Therefore, 0.54 % tensile strain was applied to the YSZ thin film. Also for this work, an all epitaxially grown thin film of YSZ/La0.7Sr0.3MnO3(LSMO)/CeO2/YSZ/Si(001) was prepared. The out-of-plane lattice parameter of YSZ was 0.5145 nm. Therefore, the YSZ thin film of YSZ/LSMO/CeO2/YSZ/Si(001) is almost relaxed, with a small amount of tensile strain (0.12 %). In-plane and out-of-plane electrical properties were measured respectively for YSZ/tht-PSi(001) and YSZ/LSMO/CeO2/YSZ/Si(001) thin films. Results show that ionic conduction was confirmed at 400 °C through constant electric conductivity against the change of oxygen partial pressure (pO2). Enhanced ionic conduction was observed for epitaxial YSZ/tht-PSi(001) thin films measured along the in-plane direction. Such enhanced ionic conduction was not observed for epitaxial YSZ/LSMO/CeO2/YSZ/Si(001) thin films measured along the out-of-plane direction. These findings suggest that enhanced ionic conduction is correlated with tensile strain in YSZ thin films.
The 76th CerSJ Awards for Academic Achievements in Ceramic Science and Technology: Review
Special Article
published : vol. 130, no. 7, July 2022
Hiromichi Ohta
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Thermoelectric energy conversion attracts increasing attention as a technology for effectively reusing waste heat. Although thermoelectric materials that show a good thermoelectric figure of merit (ZT) have been proposed thus far, they are not practical at all because they are thermally and chemically unstable and composed of toxic elements. In order to address this issue, the author focused on metal oxides as thermoelectric materials that are thermally and chemically stable and non-toxic, and succeeded in significantly improving thermoelectric ZT by using two-dimensional electron gas and elemental substitution. In 2007, the author focused on Prof. Dresselhaus’s theory that “by confining carriers in a quantum well thinner than the thermal de Broglie wavelength, the thermoelectric power can be greatly enhanced without lowering the conductivity”, and the oxide superlattice was introduced. In 2010, the author demonstrated a field-effect transistor structure on an insulator SrTiO3 crystal and measured thermoelectric power while inducing 2DEG with a thickness of 2 nm by applying a voltage, similar to an artificial superlattice. It was discovered that the thermoelectric field can be increased 5 times as much as the bulk ratio. Furthermore, in 2020, the author found that the Ba1/3CoO2 thin film with a layered crystal structure had the highest room temperature ZT of 0.11 among metal oxides.
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published : vol. 130, no. 7, July 2022
Qing Qin, Yoshio Hasegawa and Toshimitsu Tetsui
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The development of a basic process for the mass production of continuous zirconia fibers with a tensile strength of more than 2 GPa is being extensively researched. It is expected that the use of oxide/oxide composites will improve the performance of jet engines. In this study, continuous zirconia fibers with diameters and crystal sizes below 10 µm and 10 nm, respectively, were synthesized using a dry-spinning method by employing molecular-designed precursor polymers. In addition, strength-enhancing fibers were developed by improving the precursors, solvents, and infusibilization/sintering conditions. The properties of the fibers were investigated via scanning electron microscopy, X-ray diffraction, and mechanical tensile tests. Furthermore, the application of the as-prepared materials as reinforcements for ceramic matrix composites is presented.
Full Paper
published : vol. 130, no. 7, July 2022
Xiaofeng Yuan, Yixuan Wei, Hongliang Liu, Pengpeng Chang, Ying Zhou and Qianqian Gao
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The high-k [(K0.5Bi0.5)xBi1−x](WxV1−x)O4 (0 ≤ x ≤ 0.1) ceramic was prepared via the modified solid-state reaction method. When x = 0.1, the monoclinic scheelite structure was obtained at low sintering temperature. However, when x = 0.2, the impurity phase was found. After being sintered at 650 °C for 6 h, the [(K0.5Bi0.5)0.1Bi0.9](W0.1V0.9)O4 ceramic possesses the best properties with a relative permittivity of 78.7, Q × f value of 7210 GHz and a temperature coefficient of +163 ppm/°C at the frequency of 4.11 GHz. Compared with the result of the pure BiVO4 ceramic, the sintering temperature dropped from 740 to 650 °C and the relative permittivity was increased from 67.8 to 78.7. Due to the high relative permittivity and the low sintering temperature, the [(K0.5Bi0.5)0.1Bi0.9](W0.1V0.9)O4 ceramic is potential to realize the miniaturization in communication application.
Full Paper
published : vol. 130, no. 7, July 2022
Takuma Takayanagi, Akira Nasu, Fumika Tsuji, Kota Motohashi, Atsushi Sakuda, Masahiro Tatsumisago and Akitoshi Hayashi
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For the practical application of all-solid-state batteries, it is necessary to improve the performance of the solid electrolytes. We previously reported the fabrication of Na2.88Sb0.88W0.12S4, which showed the highest ionic conductivity among Na+ conducting sulfide solid electrolytes. In this study, we focused on the anion substitution of Na2.88Sb0.88W0.12S4 and evaluated oxygen substitution. Samples of Na2.88Sb0.88W0.12S4−xOx (0 ≤ x ≤ 0.5) were fabricated by a mechanochemical process and subsequent heat treatment, and structural analysis and electrochemical evaluation were performed. The solid solution of oxygen was found to proceed in the range of x ≤ 0.3. The oxygen substitution decreased the ionic conductivity, but it maintained a high ionic conductivity of more than 10−3 S cm−1. The reduction tolerance was improved by the oxygen substitution based on cyclic voltammetry measurements. An all-solid-state Na–Sn/TiS2 cell using the Na2.88Sb0.88W0.12S3.7O0.3 electrolyte operated at room temperature.
Full Paper
published : vol. 130, no. 7, July 2022
Takuya Aoyagi, Yohei Onodera, Shinji Kohara, Takashi Naito, Toshiaki Ina, Daiko Takamatsu, Taigo Onodera, Tatsuya Miyake, Shinichi Tachizono and Kei Yoshimura
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Achieving both high water durability and low glass transition temperature is crucial for the practical use of low-melting glass in hermetic sealing. In Ag2O–V2O5–TeO2 glass, we found that the increase in Ag2O content lowers glass transition temperature and improves water durability. Furthermore, the reason for the improvement of water durability is considered to be due to the increase in the coordination number of oxygen atoms around vanadium ions without the change in oxidation state, as shown by X-ray absorption fine structure measurements. We demonstrate that a Ag2O–V2O5–TeO2 glass is a key glass system for low-temperature hermetic sealing.
Full Paper
published : vol. 130, no. 7, July 2022
Chang Fa, Zhang Jungui, Lu Shijia, Guo Keke, Dai Pinqiang, Liu Chao and Zhang Xiaofeng
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High-entropy alloys (HEAs) hold promise for achieving excellence performance due to unconventional composition and structure. In this paper, the effect of FeCoCrNiAl HEAs as binder instead of Co on the microstructure of WC cemented carbide was investigated. The isothermal oxidation resistance of the WC-HEAs cemented carbides with 6, 10, 15 % was studies at 700, 800, 900 and 1000 °C. The results revealed that the microstrcture of WC-HEAs cemented carbides was dense, and the average grain sizes of WC decreased with the increase of HEAs binder content. The oxide layers containing WO3, NiWO4, and a small amounts of MWO4 (M = Co, Cr) were formed after high-temperature oxidation of WC-HEAs cemented carbides, the ratio of MWO4-to-WO3 in the WC-HEAs oxide layer increases gradually as oxidation temperature increase. The oxide films thickness of WC-10HEAs cemented carbides became thinner than that of WC-10Co at 900 °C. The oxidation kinetic curves also demonstrated that the oxidation resistance of the WC-HEAs cemented carbides was better than that of WC-Co cemented carbide except that the binder content was 6 %, and the oxidation resistance of the WC-HEAs cemented carbide was superior to WC-Co cemented carbide, which was attributed to the formation of protective oxides and MWO4 tungstate.
Full Paper
published : vol. 129, no. 12, December 2021
Niansheng GUO, Zhaoqiang CHEN, Guangchun XIAO, Qi LI, Shuai ZHANG, Mingdong YI, Jingjie ZHANG and Chonghai XU
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For the sake of enhance the cutting performance of self-lubricating ceramic tools, in this paper, we prepared self-lubricating tool materials by adding CaF2@Al2O3 coated powder with core–shell structured as solid lubricant, the cutting performance of ceramic tool materials were investigated through dry machining of hardened steel, and the wear mechanism was explored. The results showed that CaF2@Al2O3 core–shell structured solid lubricant in the ceramic tool material was more effective than CaF2 in improving the wear resistance. The addition of CaF2@Al2O3 core–shell structured solid lubricant in the ceramic tool materials can reduce the cutting force and cutting temperature. Under the same cutting conditions, compared with Al2O3/TiC/CaF2 ceramic cutting tool, the Al2O3/TiC/CaF2@Al2O3 tool had lower surface roughness of workpieces, while the main cutting force and cutting temperature are reduced by 27.7 and 52.6 % respectively in the cutting process. The wear of the rake face included micro-chipping, crater wear and adhesive wear, while the wear of flank face included micro-chipping, adhesive wear and abrasive wear. The ceramic tool with CaF2@Al2O3 core–shell structured solid lubricant obtained outstanding cutting performance.
Full Paper
published : vol. 129, no. 12, December 2021
Yuuki KAGAMI, Syuuichi YAMAMOTO, Yuta YOKOBAYASHI, Ryunosuke UCHIDA, Koki SUZUKI, Seiichi TARUTA and Toshinori TAISHI
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Polycrystalline SiC coating on large-sized SiC ceramics was investigated for its application to SiC susceptors for use in severe environments in LSI processes. The proposed coating process is simple and special gases are not used. SiC coating on the SiC substrate is achieved by positioning the ceramics above Si melt maintained in a carbon crucible in a furnace constructed using carbon materials. First, we evaluated the effect on the SiC grain size and the thickness of the SiC coating of varying the temperature and the distance maintained between a 1-inch diameter SiC substrate and the melt surface. We found that 6H-SiC grains several micrometers in size were densely deposited on the substrate, and the grain size and thickness of the SiC coating increased with increasing temperature. Next, based on these results, we achieved crystalline SiC coating on both sides of a 6-inch diameter SiC substrate. The number of carbon or SiC particles released from the SiC ceramic surface was evaluated with a submerged particle counter, and this number was found to be reduced by 99 % or more with a sample coated at 1800 °C as compared to the uncoated product. A discussion of possible chemical reactions for crystalline SiC formation is presented here based on the analysis of chemical species in the furnace using quadrupole mass spectrometers.
Full Paper
published : vol. 129, no. 12, December 2021
Du-Cheng TSAI, Feng-Kuan CHEN, Zue-Chin CHANG, Bing-Hau KUO, Erh-Chiang CHEN, Yen-Lin HUANG and Fuh-Sheng SHIEU
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ZnMgO:Al coatings were prepared by radio frequency (RF) magnetron sputtering on glass substrates, and the effects of the substrate temperature on the structural, electrical, and optical properties of ZnMgO:Al coatings were studied. The ZnMgO:Al coatings had a hexagonal wurtzite crystal structure oriented along the c-axis, regardless of the substrate temperature. Increasing the substrate temperature increased the grain sizes of the coatings and thus their Hall mobilities. The high substrate temperature also promoted the doping concentration efficiency of Al3+ ions, leading to enhanced carrier concentration. The optimal deposition was obtained at 400 °C, which led to the lowest resistivity (2.82 × 10−3 Ω cm) and 91 % transmission in the visible range. The optical bandgap increased to 3.632 eV as the substrate temperature increased to 400 °C. Wide bandgap, highly transparent, and conductive ZnMgO:Al coatings can be used as electrodes for ultraviolet photovoltaic applications.
Full Paper
published : vol. 129, no. 12, December 2021
Kohei KASUYA, Md. SHAHIDUZZAMAN, Makoto KOBAYASHI, Shu YIN, Masato KAKIHANA and Koji TOMITA
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We present a method for synthesizing brookite-type titanium dioxide (TiO2) using an emulsion-assisted hydrothermal approach and a water-soluble titanium complex with glycolic acid as a complexing agent. In this study, stirred hydrothermal synthesis was used to synthesize water-in-oil emulsions with titanium glycolate complex in the aqueous phase. The resulting brookite-type TiO2 was investigated using Raman spectroscopy for crystal polymorph identification, X-ray Diffraction to identify crystal polymorphs and crystallite size, Transmission Electron Microscope for primary particle size, and crystal shape, and Dynamic Light Scattering for TiO2 secondary particle size in aqueous dispersion. The synthesized brookite-type TiO2 was a needle-like crystal with a width between 20 and 30 nm and a length of more than 70 nm, growing in the b-axis direction at an angle of about 70° from the (120) plane. Furthermore, compared to the conventional synthesis method, the secondary particle size was smaller, and the dispersibility in water was improved. The results show that the brookite-type TiO2 dispersion obtained using the emulsion-assisted hydrothermal method can facilitate the formation of uniform films and can be applied to the electron transport layer of organic perovskite solar cells.
Full Paper
published : vol. 129, no. 12, December 2021
Dandan WEI and Wenxuan LI
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36Pb(In1/2Nb1/2)O3–30Pb(Mg1/3Nb2/3)O3–34PbTiO3 (36PIN–30PMN–34PT) ternary ceramics with morphotropic phase boundary (MPB) composition were fabricated by two-columbite precursor method. The effects of sintering temperature on phase formation, densification and electrical performance of PIN–PMN–PT ceramics were investigated in detail. It was found that the optimized sintering condition was 1240 °C for 5 h. The electric properties of the 36PIN–30PMN–34PT ceramics were dependent on sintering temperature. More importantly, the dielectric and piezoelectric constant increased as the sintering temperature increased. However, the increasing trends between electric properties and the sintering temperature were interrupted when the ceramics were sintered above 1260 °C as a result of PbO vaporization.
Full Paper
published : vol. 129, no. 12, December 2021
Ruirui LIU, Qi ZHAO and Zhijiang JI
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Ternary Au/Bi2WO6/BiOBr composites were skillfully prepared via a two-step synthetic route. The two-component Bi2WO6/BiOBr heterojunction was firstly fabricated by hydrothermal method, and Au nanoparticles (NPs) were further introduced and uniformly anchored on the surface of Bi2WO6/BiOBr, where the loaded Au NPs could be beneficial for improving visible-light absorption and adjusting photoinduced charge carriers in the heterostructure through surface plasmon resonance (SPR). In comparison with pristine Bi2WO6 and two-component Bi2WO6/BiOBr, the ternary Au/Bi2WO6/BiOBr composite exhibits a better photocatalytic activity for removal of rhodamine B (RhB) under visible light irradiation. The degradation efficiency of GTB-3 composite 1.9 times higher than that of the pure Bi2WO6 and 1.24 times than that of Bi2WO6/BiOBr. Trapping tests with different scavengers revealed that not hydroxyl radicals but superoxide radicals and photogenerated holes were highly responsible for the degradation process. The enhanced photocatalytic activity was ascribed to the synergetic effect of heterojunction effect (efficient separation of charge carriers), porous structure of Bi2WO6 (strong adsorption), SPR of Au.
Full Paper
published : vol. 129, no. 12, December 2021
Yutaka AIKAWA, Mamiko UMETSU, Toshinari MUKAI and Etsuo SAKAI
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An equation was derived to analyze carbonation phenomena in cement based on the Tomosawa theory, and it was applied to examine the difference between the cement content and degree of charcoal oxidation. Two types of fly ash cement based on ordinary Portland cement (OPC), high-alite cement (HAC), low-heat Portland cement (LHC), and moderate-heat Portland cement (MPC) were prepared, and the degree of carbonation was measured by acceleration examination. With these measurements, long-term carbonation was simulated using the new equation. Under the accelerated condition (CO2 5 %), when 18 % fly ash was added to Portland cement (OPC+FA18) and 18 % fly ash to HAC (HAC+FA18), the degree of carbonation in one month was examined relative to unmodified cement, and the carbonation rate increased by approximately 1.8 and 1.6 times, respectively. The degree of carbonation of MPC was approximately the same as that of OPC, but the carbonation of LHC was about three times greater. Therefore, fly ash cement (OPC+FA18, HAC+FA18) and LHC are more useful in the environment because these cements have a superior ability to prevent carbon dioxide release compared with that of OPC.
Full Paper
published : vol. 129, no. 12, December 2021
Shigeomi TAKAI, Yoshinobu TAWA, Masashi TAKEMOTO, Jian KANG, Takeshi YABUTSUKA and Takeshi YAO
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LiMn2O4 has been prepared by means of high-energy ball-milling of Li2CO3 and MnCO3 followed by one-pot sintering. Milling at 800 rpm for 4 h with sintering at 700 °C for 12 h leads the enhanced cathode performance as 123.5 mAh g−1 of initial discharge capacity under 1 C charge–discharge rate, retaining 95.1 and 91.6 % of capacity after 100 and 200 cycles, respectively. Mechanochemical reaction facilitates the sintering reaction to form the favorable microstructure homogeneously without second phase. Relaxation analysis showed that, at the charging around x = 0.2 for LixMn2O4, the sample prepared by optimal milling time varies mainly lithium concentration in Li-rich phase, while excessively milled sample alter the molar ratio of Li-rich and Li-lean phases. This indicates that optimal milling time allows the sample to undergo the less structural change at the charging, which enables the improved cycle performance.
Full Paper
published : vol. 129, no. 12, December 2021
Dasong PENG, Xiaodong WANG, Yanchao REN, Xiaoqiang DU and Zhihua DAI
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In this work, based on the sol–gel and titration technology, an innovative method to prepare the yttria stabilized ZrO2–Al2O3 composite beads which can greatly improve the bead properties is proposed. Using this method, the yttria stabilized ZrO2–Al2O3 composite beads samples with different proportion of alumina component were prepared and tested. The density results show that the density of the ceramic beads is very close to the theoretical value, which implies that the new method can prepare the beads with high compactness and without containing pores. Vickers hardness results show that the hardness of the composite beads is higher than the zirconia beads without containing alumina. The SEM analyses show that the average grain size of the composite beads is about 180 nm, much smaller than that of the beads prepared by the conventional rolling process. X-ray diffraction results show that there is no monoclinic phase in the composite beads after sintering at 1250 °C. The EDS analyses show that the aluminum element exists in composite beads and the alumina grains are evenly distributed. Furthermore, the beads sintering temperature using this new process can achieve low-temperature which is about 1250 °C, much lower than that of the beads prepared by the conventional rolling process.
Note
published : vol. 129, no. 12, December 2021
Yuki NAKASHIMA, Hideki HYUGA, Kiyoshi HIRAO, You ZHOU, Manabu FUKUSHIMA and Norimitsu MURAYAMA
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Silicon nitride ceramics have attracted increasing attention as insulated heat-dissipating substrates for power modules due to their high thermal conductivity and mechanical strength. However, there are very few reports on their dielectric breakdown strength, which was only evaluated for the substrates with thicknesses between 250 and 640 µm, though thinner substrates are preferable for attaining better performance of the module. In this work, dielectric breakdown of sintered silicon nitride substrates with thicknesses ranging from 285 to 15 µm was evaluated for the first time. Average breakdown strength increased from 36.38 to 103.80 kV/mm with decreasing thickness from 285 to 15 µm. It should be noted that the silicon nitride specimen had very high dielectric breakdown voltage of 1.5 kV even with a thickness as small as 15 µm.
Note
published : vol. 129, no. 12, December 2021
Yuki OBUKURO and Shigenori MATSUSHIMA
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The electronic structure of Pr-doped ZrSiO4 is calculated using modified Becke–Johnson potential plus on-site Coulomb interaction (MBJ + U). The minimum energy gap of ZrSiO4 calculated using the MBJ method is 5.8 eV, which is close to the experimental value. When a Pr atom replaced one of Zr atoms, strongly localized Pr 4f states appear in the forbidden gap of ZrSiO4. By considering the on-site Coulomb interaction in addition to the MBJ potential, the empty Pr 4f states appear about 2 eV above the valence band maximum of ZrSiO4. Compared with generalized gradient approximation (GGA), MBJ, and GGA + U approaches, MBJ + U better describes the position of empty Pr 4f states for Pr-yellow pigment.
Full Paper
published : vol. 129, no. 11, November 2021
Manabu KOIDE, Khaled JABRI and Tomohiro SATO
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The effect of TiB2 and TiN contents on the phase formations and their mechanical properties in the binary systems of Ti–TiB2 and Ti–TiN, and in the ternary system of Ti–TiB2–TiN was investigated. In the binary systems, TiB2 and TiN addition improved the hardness of Ti but reduced its bending strength. In the ternary system of Ti–TiB2–TiN, the addition of TiB2–TiN mixture to Ti further improved the hardness to around Hv = 10.0 GPa compared to 7.0 GPa in the binary systems, but it did not improve the bending strength. The increase of hardness in the binary system of Ti–TiB2 was mainly attributed to the formation of TiB (or non-stoichiometric solid solution of TiB1−x) and to remaining TiB2 in samples with high TiB2 contents. The reduction of bending strength, however, was attributed to the disappearance of metallic Ti, to the formation of TiB1−x, and to porous structure in samples with high TiB2 contents. The increase of hardness in the binary system of Ti–TiN was attributed mainly to the formation of non-stoichiometric solid solution of TiN1−x. The reduction of bending strength was attributed to the large crystal growth of flake like structure of TiN1−x. The further improvement of hardness in the ternary system of 80Ti–20(TiB2–TiN) was attributed to the formation of fine crystals of TiB (or TiB1−x) within the flake like structure of N-diffused α(Ti) crystal phase. The reduction of bending strength is mainly attributed to the large growth of flake like structure of N-diffused α(Ti) crystal phase.
The 75th CerSJ Awards for Academic Achievements in Ceramic Science and Technology: Review
Special Article
published : vol. 129, no. 11, November 2021
Shinji TAMURA
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Various kinds of conducting ion species in solids have been discovered by selecting the NASICON-type three-dimensional network structure. By introducing high-valence Nb5+ into NASICON-type solids, both the thermal stability and crystallinity of NASICON-type trivalent cation conductors were simultaneously improved, leading to 13 kinds of trivalent cations that were newly reported to migrate in solids. In addition, highly selective low-temperature operative gas sensors were successfully fabricated using the (Al0.2Zr0.8)20/19Nb(PO4)3 solid, which possesses a high trivalent cation conductivity of over 10−4 S·cm−1 at 600 °C, as well as high thermal and chemical stabilities.
The 66th CerSJ Awards for Advancements in Ceramic Science and Technology: Review
Special Article
published : vol. 129, no. 11, November 2021
Akihiko ITO
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High-intensity laser irradiation promotes a chemical reaction between the vapor phase and the film surface in the chemical vapor deposition (CVD) process, resulting in a high-speed deposition and a significant oriented growth of various kinds of oxides, nitrides, carbides, and their compounds and composites. TEM observation revealed unique microstructures, such as columnar, feather-like, and single-crystalline growth, in the produced CVD coatings. This CVD process enables the combination of high-speed epitaxial growth and excellent properties for structural and functional ceramic coatings. Traditional ceramics, such as Al2O3, TiO2, Al2TiO5, BaAl12O19, BaTiO3, YBa2Cu3O7−δ, and CeO2, can be still highly valued as practical materials by functionalization of ceramic coatings with the control of orientation and nanostructure.
Full Paper
published : vol. 129, no. 11, November 2021
Jingren LI, Wenzhong LU and Hai JIANG
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Dense silicon carbide (SiC) ceramics were fabricated through hot-pressing with a novel combination of rare earth oxides and fluorides (CeO2–CeF3, Nd2O3–NdF3, Gd2O3–GdF3 and Y2O3–YF3) as additive. Effects of these additive combinations on microstructure, phase composition, flexural strength and thermal conductivity of SiC ceramics were evaluated. The samples with 1 wt %Nd2O3–2 wt %NdF3 (1Nd2Nd sample) and 1 wt %Gd2O3–2 wt %GdF3 (1Gd2Gd sample) additive exhibited the highest thermal conductivity of 187.8 W/m·K and highest flexural strength of 607.6 MPa respectively. Impedance spectroscopy analysis was employed to further investigate the variations of defects and impurities in SiC ceramics. 1Nd2Nd sample exhibited a higher fitting grain and grain boundary resistance that suggested a lower concentration of V””Si vacancies than other samples, which resulted in a higher thermal conductivity. On the other hand, the highest flexural strength of 1Gd2Gd sample was attributed to a combined effect of its small grain size, contiguous microstructure and low content of grain boundary phases. All in all, Re2O3–ReF3 additive combinations are suitable for tailoring and improving the thermal conductivity and flexural strength of SiC ceramics.
Full Paper
published : vol. 129, no. 11, November 2021
Sung Il YUN, Sahn NAHM and Sang Whan PARK
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Liquid phase bonded (LPB) porous SiC with neck bonding phases consisting of yttrium aluminate (Y4Al2O9, Y3Al5O12), yttrium silicate (Y2Si2O7), and Al2O3 were fabricated using varying amounts of an Al2O3–Y2O3–SiO2 bonding additive in Ar at 1500 °C for 1 h. LPB porous SiC ceramics exhibited unimodal pore-size distributions, porosities of 36.6–44.8 %, and pore sizes of 7.7–8.5 µm. The particle-size distribution of SiC powders was an important factor in determining the pore characteristics, including pore-size distribution, pore shape, porosity, and pore size, and the flexural strength as well as the gas permeability of LPB porous SiC ceramics. The porosity and pore size increased, and the pore-size distribution narrowed by using SiC powders with a narrow size distribution. The flexural strength of porous SiC varied in the range of 39.7–66.7 MPa and was mainly dependent on the porosity, pore shape, pore size, and solid boning area varied by the SiC particle-size distribution. A relatively high permeability (1.28–1.84 × 10−12 m2) of LPB porous SiC was attained mainly due to the unimodal pore size distribution of pores with sizes of 7.7–8.5 µm.
Full Paper
published : vol. 129, no. 11, November 2021
Zhongfeng XIA, Zhoufu WANG, Yan MA, Hao LIU and Xitang WANG
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Drying process is necessary in the preparation and application of refractory castables. In this work, the effects of conventional drying, microwave drying and freeze drying on the composition and properties of cured calcium aluminate cement (CAC) pastes were comparatively investigated. The differences in the microstructures evolution process under various drying mechanisms were discussed. The results show that metastable CAH10 and C2AH8 are completely transformed into stable phases in the conventional dried pastes, while a small amount of flaky C2AH8 remained in pastes dried via microwave. Nevertheless, the major hydrates in the freeze-dried pastes are CAH10 and C2AH8. In addition, the pores in pastes dried by microwave are mainly distributed in the range of 20–2000 nm, while the freeze-dried pastes contain more gel pores and show higher elastic modulus. A new approach to effectively regulate the pore structure of CAC bonded materials via non-conventional drying methods is proposed in the present work.
Full Paper
published : vol. 129, no. 11, November 2021
Takeo HYODO, Azusa IWANAGA, Keijiro ISHIDA, Kai KAMADA, Taro UEDA and Yasuhiro SHIMIZU
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Fundamental gas-sensing properties of porous (pr-)In2O3 powders loaded with and without 0.5 mass % noble metal (pr-0.5N/In2O3 and pr-In2O3, respectively, N: noble metal (Au or Pd)) to NO2, H2, and ethanol balanced with dry air were investigated at 30 °C under UV-light irradiation (main wavelength: 365 nm). The spherical pr-0.5N/In2O3 and pr-In2O3 powders were prepared by ultrasonic-spray pyrolysis employing polymethylmethacrylate microspheres with a diameter of ca. 70 nm, which were synthesized by ultrasonic-assisted emulsion polymerization. The Au loading largely improved the NO2 response of the pr-In2O3 sensor, a ratio of the resistance in NO2 to that in air, especially under weak UV-light irradiation, because of the relatively large resistance in air. On the other hand, the Pd loading efficiently increased the difference in the conductance of the pr-In2O3 sensor between in NO2 and in air under the whole UV-light irradiation range. The UV-light irradiation is effective in improving the NO2-sensing properties of these sensors at room temperature, but the sensing performance was a little inferior to that operated at elevated temperatures under no UV-light irradiation. These sensors also responded to reducing gases, H2 and ethanol, under UV-light irradiation, and the responses to ethanol were much larger than those to H2. However, the responses to both the gases were much smaller than that to NO2.
Full Paper
published : vol. 129, no. 11, November 2021
Kazuya UJIIE, Takashi KOJIMA, Kosuke OTA, Shuhei HOSOYA and Naofumi UEKAWA
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Strontium titanate (SrTiO3) particles are expected to be applied to various catalysts, and many kinds of synthesis procedures of SrTiO3 particles with a high specific surface area have been proposed. This study investigates a synthesis procedure of preparing SrTiO3 particles with a high specific surface area by minimizing the crystallization temperature to the least possible value. The SrTiO3 particles are prepared by maintaining spherical hydrous titania particles with smooth or porous surfaces in highly concentrated strontium hydroxide solutions at ≤120 °C. When porous hydrous titania particles are used as the raw material and the Sr/Ti ratio in the reaction solution is set at 10, spherical protrusions of SrTiO3 develop on the surface of the original hydrous titania, even at a low temperature (25 °C). Single-phase SrTiO3 particles with spherical protrusions composed of very fine crystallites are obtained by treatment at 40 °C for 24 h. These particles have a high BET specific surface area of 237 m2 g−1. The process developed herein is eco-friendly and effective for fabricating various perovskite-type compounds with a high specific surface area.
Note
published : vol. 129, no. 11, November 2021
Kunihiko KATO, Takafumi SUDO, Yunzi XIN and Takashi SHIRAI
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To create a highly photocatalytic performance in addressing the global environmental issues, we develop a highly efficient photocatalyst engineered by a combination of control of exposed facet in TiO2 and composite with the non-noble metal nanoparticle. The formation of a fluorinated surface during crystal growth assists the morphology control of TiO2 with coexposed {001}/{101} facets. In addition, the deposition of nano-sized Sn particles (>10 nm) is achieved via photochemical reduction on the faceted TiO2 from anhydrous chelated tin(II) complexes by amino acid. Here, the bidentate ligands (i.e., carboxyl and amino group) in proline molecular play a vital role in associating the strong interaction between TiO2 surface and chelated Sn complexes. The optimal balance in the ratio of exposed {001}/{101} facets and loading amount of Sn nanoparticles are essential factors for an enhancement of photocatalytic activity for efficiently consume photo-exited electrons in the degradation of azo-dye water pollutants.
Full Paper
published : vol. 129, no. 10, October 2021
Chihiro KATO, Nobutomo OTSUKA, Kayano SUNADA, Toshihiro ISOBE, Sachiko MATSUSHITA, Takeshi NAGAI, Hitoshi ISHIGURO and Akira NAKAJIMA
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Using hydrothermal processing, we prepared a cerium bismuth solid solution oxide ((Ce0.8,Bi0.2)O2−δ, CBO) and a cerium lanthanum solid solution oxide ((Ce0.8,La0.2)O2−δ, CLO). The resultant powders possessed fluorite-type crystal structure. They also decomposed 2-naphthol in water in the dark. From their valence change and temperature dependence, we infer that the Mars–van Krevelen (MvK) mechanism of Ce contributes to this decomposition activity. These materials showed higher decomposition activity under visible light. Modification of CoOx onto these materials enabled an apparent bandgap decrease and the MvK mechanism of Ce and Co, which led to higher decomposition activity in the dark and under visible light. The CBO activity was higher than that of CLO on the decomposition of 2-naphthol in water, but the CLO antiviral activity was higher than that of CBO. Results suggest that the CLO antiviral activity results from virus deactivation by direct contact with the powder surface.
Express Letter
published : vol. 129, no. 10, October 2021
Yusuke DAIKO, Junki KATO, Sawao HONDA and Yuji IWAMOTO
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A few GPa-order high-pressure impedance measurement was performed by utilizing an indentation method, which is often used to evaluate mechanical characteristics, and the alternating current (AC) impedance method simultaneously. We succeeded in estimating the activation volume (Δ V = 3.2 cm3/mol) for O2− ion conduction of YSZ with a single sweep of load at 0.25 N/s up to 25 N. Such a quick and easy method for determining Δ V is completely new that has not been proposed so far.
Full Paper
published : vol. 129, no. 10, October 2021
Jaegyeom KIM, Hiroaki KATSUKI, Oratai JONGPRATEEP, Sansanee BOONSALEE and Jae-Hwan PEE
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Alumina, mullite, and cordierite powder were added to a whiteware porcelain slurry and sintered at 1280 °C to investigate the correlation between porcelain composition and strength. The X-ray diffraction patterns of the sintered bodies show that no new phase was formed, and that the added material remained intact. Except for the sample group to which cordierite was added, the strength increased as the additive content increased. A Rietveld quantitative analysis indicated that the amorphous phase decreased with increasing additional alumina and mullite content, while the amorphous content remained constant regardless of the additional cordierite content. The decrease in the amorphous content increased the strength of the porcelain, which, in the case of the sample with 15 wt.% alumina, increased by 57 %. The dramatic increase in strength is attributed to the increase in residual stress due to the difference in the thermal expansion coefficient between the alumina and the amorphous phase, as well as the increased formation of mullite by the addition of alumina.
Full Paper
published : vol. 129, no. 10, October 2021
Hiromichi ICHINOSE, Mitsunori YADA and Kohjiro HARA
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Titanium oxide films were prepared from peroxotitanium complex aqueous solution containing a peroxo complex of vanadium, molybdenum or tungsten of 2, 5, 10 mol % by heating at 200 °C for the purpose of suppressing the photocatalytic activities that may be developed by crystallization during long-term use as a prevention film against potential-induced degradation (PID) of crystalline silicon (c-Si) photovoltaic (PV) module. The films containing those dopants crystallized to anatase by hydrothermal treatment at 100 °C for 15 h as an acceleration test, but hardly showed any photocatalytic activity. According to the lattice constants, X-ray photoelectron spectroscopy analyses and UV–visible light reflection spectra, it was estimated that vanadium (V), molybdenum (VI) and tungsten (VI) were substituted with titanium (IV) in titanium oxide heated at low temperature of 200 °C. The titanium oxide films containing the dopants of 2 mol % were coated at 200 °C onto the rear side of front cover glass with 200 nm thickness. No significant PID was observed in the c-Si PV modules based on the film-coated glass by a PID test by applying −1000 V at 85 °C for 2 h.