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Feature: Cutting edge researches on electroceramics, 2017
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published : vol. 126, no.5, May 2018
Takuya HOSHINA, Ryuichi SASE, Junji NISHIYAMA, Hiroaki TAKEDA and Takaaki TSURUMI
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We prepared oxygen-deficient strontium titanate ceramics and measured the THz dielectric spectra to discuss the effect of oxygen vacancies on the intrinsic dielectric permittivity. In the presence of oxygen vacancies, the lattice volume of strontium titanate increased. First-principles calculation revealed that the expansion of the lattice originated from repulsion between the oxygen vacancies and cations, causing a decrease in the covalency of the Ti–O bonding. THz dielectric measurement using a far-infrared spectroscopic ellipsometer made it clear that the Slater-type phonon mode hardened and then the intrinsic permittivity of strontium titanate decreased in the presence of oxygen vacancies.
Feature: Cutting edge researches on electroceramics, 2017
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published : Feature: Cutting edge researches on electroceramics, 2017
Takao SHIMIZU, Kiliha KATAYAMA and Hiroshi FUNAKUBO
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Ferrolectric orthorhombic HfO2-based films are potential candidates for future ferroelectirc applications. The stability of the orthorhombic phase of epitaxial YO1.5-substituted HfO2 films on (111) yttria-stabilized zirconia substrates was investigated for various compositions, thicknesses and underlying layers. In the case of 14 nm-thick films, only 7 mol % film consisted of a single orthrohombic phase. With decreasing amount of YO1.5 or increasing thickness, the paraelectric monoclinic phase formed in the films. On the contrary, the highly symmetric phase was grown by the increasing amount of YO1.5. The effect of the underlying layer was also investigated. Differences in the degree of relaxation of the buffer layer give different amounts of the monoclinic phase. These results imply the importance of the compostions as well as of the strain state to (111)-oriented epitaxial Y-substituted HfO2 films.
Feature: Cutting edge researches on electroceramics, 2017
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published : vol. 126, no.5, May 2018
Kazuki OKAMOTO, Tomoaki YAMADA, Jun YASUMOTO, Kentaro NAKAMURA, Masahito YOSHINO and Takanori NAGASAKI
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Self-assembled Pb(Zr,Ti)O3 (PZT) nanorods were grown by pulsed laser deposition (PLD) at an elevated oxygen pressure. PZT grew as a film in the initial growth stage and formed nanorods upon further deposition. The influence of the substrate temperature, target-substrate distance, and Pb composition of the targets on nanorod growth was investigated. It was found that the average radius of the PZT nanorods was larger at higher substrate temperatures and longer target-substrate distances, which can be explained respectively by the enhanced surface diffusion and shadowing effect of the PLD species. The results of this study can contribute to controlling the sizes of PZT nanorods to tune their piezoelectric response.
Feature: Cutting edge researches on electroceramics, 2017
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published : vol. 126, no.5, May 2018
Takahisa SHIRAISHI, Yoshiharu ITO, Mutsuo ISHIKAWA, Hiroshi UCHIDA, Takanori KIGUCHI, Minoru K. KUROSAWA, Hiroshi FUNAKUBO and Toyohiko J. KONNO
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{001}c-oriented (K0.86Na0.14)NbO3 thick films were prepared at 240°C on (100)cSrRuO3//(100)SrTiO3 substrates by repeated hydrothermal deposition technique. The film thickness was found to increase linearly with the number of deposition cycles, and 60 µm-thick film was obtained after nine repetitions of the deposition. The K/(K+Na) ratio of the deposited thick films, measured by X-ray fluorescence spectroscopy, showed constant values regardless of the number of deposition cycles. Cross-sectional scanning electron microscopy images revealed uniformity of the obtained dense films with no obvious micro cracks and pores. Structural characterization based on X-ray diffraction, XRD 2θ-ω patterns and X-ray pole figure measurement, showed that the epitaxial relationship between the films and substrates with a {001}c orientation was maintained throughout the deposition cycles. In addition, cross-sectional Raman spectra showed that 60 µm-thick (K0.86Na0.14)NbO3 film had an orthorhombic structure. The dielectric constant, εr, and tan δ showed frequency dependence. The average remanent polarization measured at 100 Hz was 8 µC/cm2.
Feature: Cutting edge researches on electroceramics, 2017
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published : vol. 126, no.5, May 2018
Shunsuke NARUSHIMA, Rina SHIMONISHI, Manabu HAGIWARA and Shinobu FUJIHARA
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A facile synthesis method of delafossite-type CuYO2 using a layered yttrium hydroxide (LYH) was developed. LYH microplates and Cu2O nanoparticles were both prepared from aqueous solutions and used as raw materials for the solid-state reaction to form CuYO2. It was found that CuYO2 could be obtained by heating LYH–Cu2O mixed powder at 900°C for 4 h under a N2 atmosphere. Although the product contained a slight amount of Y2O3, the heating time used in the proposed method was much shorter than that required for the conventional synthesis method via the Cu2Y2O5 precursor phase. Analysis of the X-ray diffraction pattern showed that the CuYO2 powder synthesized using LYH contained the 3R-type polymorph as the major content, whereas a larger content of the 2H-type polymorph was included in the powder synthesized by the conventional method. Based on these results, a topotactic reaction maintaining the layered structure of LYH was proposed as the formation mechanism for CuYO2 in LYH–Cu2O mixed powder.
Feature: Cutting edge researches on electroceramics, 2017
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published : vol. 126, no.5, May 2018
Keigo NAKAMURA, Kotaro FUJII, Eiki NIWA and Masatomo YASHIMA
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Metal oxides containing the divalent zinc cation (Zn2+, d10 electronic configuration) as an essential element are promising candidates for oxide-ion conductors, because there are several good oxide-ion conductors containing other d10 cations, such as Ga3+ and Ge4+. In the present study, we have found a new structure family of oxide-ion conductors, BaY2CuO5-type (BaCuY2O5-type) BaR2ZnO5 compounds (R = rare earths). BaR2ZnO5 compounds with a BaY2CuO5-type structure were found to be good candidates for oxide-ion conductors by the bond-valence method. BaR2ZnO5 compounds (R = Sm, Gd, Dy, Er, and Ho) were synthesized by solid-state reactions, and their electrical conductivities and crystal structures were investigated. Rietveld analyses of BaR2ZnO5 (R = Sm, Gd, Dy, Er, and Ho) using synchrotron X-ray powder diffraction data gave good fitting for the BaY2CuO5-type structure. BaHo2ZnO5 had the highest total electrical conductivity in air among BaR2ZnO5 compounds (R = Sm, Gd, Dy, Er, Ho). Oxide-ion conduction was confirmed for BaHo2ZnO5 by electrical conductivity measurements conducted under various oxygen partial pressures. Neutron powder diffraction data of BaHo2ZnO5 were analyzed by the Rietveld method, and the oxide-ion conduction paths were investigated by the bond-valence method.
Feature: Cutting edge researches on electroceramics, 2017
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published : vol. 126, no.5, May 2018
Takuto OSHIMA, Takuya HOSHINA, Takaaki TSURUMI, Kheirreddine LEBBOU and Hiroaki TAKEDA
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We report the effects of Sr or Ba substitution on the crystal growth and electrical and mechanical properties of Ca2Al2SiO7 (CAS) piezoelectric single crystals, which are suitable for use in high-temperature pressure sensors. Ba was scarcely incorporated in the crystal lattice of CAS. Strontium-substituted CAS single crystal with a nominal chemical composition Ca0.75Sr1.25Al2SiO7 (CSAS125) was grown by the Czochralski method. Although the piezoelectric modulus d31 of CSAS125 is a bit lower than that of the CAS crystal, the rupture strength of the (XYt)45° rotation cut substrate of CSAS125 crystal was 170 MPa, which was 1.2 times higher than that of CAS crystal. By considering the rupture strength and the apparent piezoelectric d*31 coefficient calculated for the crystal rotation cut of CAS crystal, the CSAS125 crystal substrate with a rotation cut of (XYt)25° was found to indicate a rupture strength of 220 MPa and a piezoelectric d31 coefficient of approximately 2 pC/N.
Feature: Cutting edge researches on electroceramics, 2017
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published : vol. 126, no.5, May 2018
Yuya HATTORI, Ichiro FUJII, Shirou OOTSUKI, Masahito FURUKAWA, Satoshi WADA and Shintaro UENO
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To meet recent requirements for high-performance dielectric capacitors, we have attempted to develop new boundary layer (BL) ceramic capacitors consisting of conductor grains epitaxially covered with insulator boundary layers to improve their dielectric breakdown strength. First, we attempted to synthesize conductor-insulator core–shell particles with epitaxial interfaces, because the desired BL capacitors can be prepared by assembling these core–shell particles. One of the conductive perovskite oxides, lanthanum nickel oxide (LaNiO3, LN), was selected as the conductor layer, and bismuth potassium titanate [(Bi1/2K1/2)TiO3, BKT], which has a similar lattice constant to LN, was selected as the insulator layer. LN nanoparticles synthesized by the sol–gel method were mixed with the titanium oxide (TiO2) and bismuth nitrate [Bi(NO3)3] in the KOH aqueous solution, and hydrothermal treatment was performed at 160°C. LN–BKT powders could be obtained in the presence of the Bi and Ti sources without decomposition of LN. This fact suggests that the BKT coating layers formed initially on the surface of the LN nanoparticles and prevented a decomposition reaction of LN in the KOH aqueous solutions. The formation of a core–shell structure in the LN–BKT powders was confirmed by scanning transmission electron microscopy-energy dispersive X-ray spectroscopy, and high-resolution transmission electron microscopy observation revealed epitaxial growth of a BKT shell layer on the LN core nanoparticles.
Feature: Cutting edge researches on electroceramics, 2017
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published : vol. 126, no.5, May 2018
Tomoya AIZAWA, Ichiro FUJII, Shintaro UENO and Satoshi WADA
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Dense Mn-added 0.3BaTiO3–0.1Bi(Mg1/2Ti1/2)O3–0.6BiFeO3 (0.3BT–0.1BMT–0.6BF) ceramics were fabricated by spark plasma sintering of 0.3BT–0.1BMT–0.6BF powders with different powder sizes of 0.3, 1.0, and 1.4 µm. It was found that use of larger powders suppressed Bi volatilization during the sintering, which was judged by maintained perovskite A site/B site component (A/B) ratios of 1.000 and 0.997 for the 1.0 and 1.4 µm samples and a decreased A/B ratio from 1.000 to 0.998 for the 0.3 µm sample. Grain sizes of the ceramics prepared from the 0.3, 1.0, and 1.4 µm powders were 0.7, 1.2, and 1.9 µm, respectively. These results contributed to increased remanent polarizations of 6.7, 28.3, and 36.6 µC/cm2 and maximum electric-field-induced strains/applied electric fields (Smax/Emax) of 251, 332, and 362 pm/V for the 0.3, 1.0, and 1.4 µm samples, respectively. Comparison with conventionally sintered ceramics was also made.
Feature: Cutting edge researches on electroceramics, 2017
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published : vol. 126, no.5, May 2018
Sangwook KIM, Gopal Prasad KHANAL, Hyun-Wook NAM, Minsu KIM, Ichiro FUJII, Shintaro UENO, Chikako MORIYOSHI, Yoshihiro KUROIWA and Satoshi WADA
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The electric field-dependent crystal structures and electrical properties were investigated in the 0.67BiFeO3–0.33BaTiO3 (BF33BT) lead-free piezoelectric ceramics. The room temperature synchrotron radiation X-ray diffraction (SR-XRD) patterns measured, without the application of an electric field, revealed all the peaks to be single suggesting the cubic like crystal structure of the BF33BT system. The domain switching was ascertained in the PE hysteresis loop and SE curve meanwhile, SR-XRD patterns exhibited beyond doubt single peak. In order to study the electric field induced structural phase transition, SR-XRD was measured in BF33BT ceramics as a function of electric field. The electric field applied up to 40 kV/cm with bipolar cycling was parallel along the longitudinal lattice response direction that was similar for the piezoelectric response measuring method. The shift of SR-XRD peaks to lower and/or higher angle in comparison to the peak position of zero field-SR-XRD was found to depend on the direction and intensity of the applied electric field. The peak shape under maximum electric field was quite same that of SR-XRD patterns at zero electric field. Importantly, the single peak shape was maintained for all the SR-XRD measured under the electric field. Therefore, the electric field induced structural phase transition did not occur in the BF33BT ceramics.
Feature: Cutting edge researches on electroceramics, 2017
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published : vol. 126, no.5, May 2018
Ken-ichi MIMURA and Kazumi KATO
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Single-crystalline barium zirconate titanate nanocubes (BZxT NCs; x is Zr contents) with various composition of Zr/Ti ratio were synthesized by hydrothermal method using water-soluble titanium and zirconium complex and surfactants. The highly-ordered assemblies of the BZT NCs were directly fabricated on the substrate by dip-coating method with low withdrawal rate. High dielectric constant above 4200 and relative low loss tangent below 1% with extremely small frequency dependence were achieved in the case of BZ0.2T NC assembly. The temperature dependence of capacitance of BZ0.1T NC assembly was quite small from −60 to 150°C. A specific peak in the Raman spectra of BZ0.2T NC assembly was slightly shifted to lower wavenumbers from 294 to 288 cm−1 after heat-treatment which meant the change of local bonding condition was induced by local strains at the interfaces. Zr-substitution and local strain synergistically affected to the dielectric properties of BZT NC assemblies.
Feature: Cutting edge researches on electroceramics, 2017
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published : vol. 126, no.5, May 2018
Yoko TAKADA, Ken-ichi MIMURA and Kazumi KATO
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Cubical Pb(Zr,Ti)O3 (PZT) crystals (PZT cubes) were synthesized using a hydrothermal method at different synthesis temperatures from 140 to 220°C. The Pb(Zr0.52Ti0.48)O3 precursor solution was prepared from Pb(CH3COO)2·3H2O, Zr(OH)[(OCH(CH3)COO]3(NH4+)3, and titanium (IV) bis(ammonium lactato)dihydroxide. In this study, the effects of synthesis temperature on the shape, morphology, and crystallinity of PZT crystals were investigated. We successfully obtained PZT cubes possessing faceted structures without circular shaped PX-phase (Ti-rich PZT) at a synthesis temperature of 180°C; these PZT cubes consisted of perovskite phase without any non-ferroelectric pyrochlore phase. Precise analysis based on selected area electron diffraction and energy-dispersive X-ray spectroscopy revealed that PZT cube was a single crystal and the chemical composition of PZT cubes was closed to the nominal composition of the PZT precursor solution, respectively. PZT cubes with single perovskite phase could be synthesized at a lower temperature of 180°C by the hydrothermal method, compared with conventional methods such as sol–gel process and metal organic decomposition method. The piezoelectric properties were confirmed for single PZT cubes using the piezoresponse force microscopy mode of a scanning probe microscope.
Feature: Cutting edge researches on electroceramics, 2017
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published : Feature: Cutting edge researches on electroceramics, 2017
Shunsuke HONDA, Kiyoto SHIN-MURA and Kazuya SASAKI
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Concentrating 6Li isotopes, which exist only approximately 7.6% in nature, to 40 to 90%, is necessary for development of thermal fusion reactors, which are promising as next-generation base-load energy systems. We investigated the possibility of 6Li enrichment by electrochemical pumping using La0.57Li0.29TiO3 solid lithium electrolytes. We also clarified the influence of potential application profiles on separation efficiency. Giving a potential difference to electrodes prepared on both sides of the electrolyte made the electrode on the lithium solution side positive and concentrated 6Li. The efficiency of lithium isotope enrichment was affected by the potential application profile. An intermittent potential application concentrates 6Li with high efficiency. In an intermittent potential application in which the electrode on the lithium solution side was positive, an 6Li concentration with higher efficiency was achieved when a small negative potential was applied to the lithium solution side electrode while suspending application of the positive potential.
Feature: Cutting edge researches on electroceramics, 2017
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published : vol. 126, no.5, May 2018
Atsushi TSU-URA, Hirotaka TORII, Takuya HASEGAWA, Dai MURAYAMA, Sun Woog KIM, Kazuyoshi UEMATSU, Kenji TODA and Mineo SATO
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Polytetrafluoroethylene (PTFE), composed of fluorine and carbon atoms, has a potential to produce carbon-coated fluorides in the calcination of inorganic compounds. We synthesized high voltage cathode material for Na ion secondary battery, Na2FePO4F, using PTFE as the carbon-coating and fluorine source. The Na2FePO4F carbon-coated by a thermal decomposition of PTFE showed high discharge capacity (64.4 mAh g−1) at the first cycle of galvanostatic cycling by the improvement of conductivity.
Feature: Cutting edge researches on electroceramics, 2017
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published : vol. 126, no.5, May 2018
Wataru UNO, Kotaro FUJII, Eiki NIWA, Shuki TORII, Ping MIAO, Takashi KAMIYAMA and Masatomo YASHIMA
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Crystal structure and neutron scattering length density distribution of a pyrochlore-type ytterbium titanate Yb2Ti2O7 have been investigated by in situ neutron powder diffraction measurements at 293 and 1173 K, Rietveld analysis and maximum-entropy method (MEM). In the MEM neutron scattering length density distributions of Yb2Ti2O7, the oxide ion O48f bonding to Ti cation was relatively localized at lower temperature of 293 K, while it was largely distributed at a higher temperature of 1173 K. At 1173 K, one oxide-ion diffusion path along the 〈110〉 unshared edge of TiO6 octahedron was clearly visualized and the other oxide-ion diffusion path along 〈100〉, strictly 〈2 −8x(O48f) + 3 8x(O48f) − 3〉, shared edge of TiO6 octahedron was also indicated. Here x(O48f) is the atomic coordinate x of O48f anion. The MEM neutron scattering length density distribution and difference bond valence sum map at 1173 K strongly suggested that the energy barrier for oxide-ion migration along 〈110〉 directions was lower than that along the 〈100〉 one. Oxide ions three-dimensionally diffuse through both the 〈110〉 and 〈100〉 paths across the unit cell.
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published : vol. 126, no.5, May 2018
Li LONGBIAO
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In this paper, the out-of-phase (OP) thermomechanical fatigue (TMF) hysteresis of fiber-reinforced ceramic-matrix composites subjected to different loading sequences has been investigated. The relationships between the OP TMF hysteresis, fiber/matrix interface debonding/sliding and multiple loading sequence have been established. The OP TMF hysteresis loops and interface damage for different loading sequences, cycle numbers and thermal cyclic temperature ranges have been analyzed. Comparisons of OP TMF hysteresis between single and multiple loading sequences have been conducted. The stress–strain hysteresis loops and fiber/matrix interface debonding/sliding of cross-ply SiC/MAS composites subjected to single and multiple loading sequences have been predicted.
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published : vol. 126, no.5, May 2018
Tao XIAN, Lijing DI, Xiaofeng SUN, Jun MA, Yongjie ZHOU and Xuegang WEI
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Au–SrTiO3 nanocomposites were prepared using a photocatalytic reduction method by which the Au nanoparticles with particle size of 7–26 nm were deposited on the surface of SrTiO3 particles with an average diameter of ∼55 nm. The structure, morphology and optical properties of products were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, Transmission electron microscopy and UV–visible diffuse reflectance spectroscopy. It is found that the loaded Au nanoparticles on SrTiO3 particles exist in the metallic state, and the surface plasmon resonance absorption band centered around 557 nm is obviously detected in the diffuse reflectance spectra of Au–SrTiO3 nanocomposites. The photocatalytic activities of samples toward the degradation of dyes (acid orange 7 and methyl orange) were evaluated under simulated sunlight and visible light irradiation. The results indicate that the decoration of Au nanoparticles can effectively improve the photocatalytic activity of SrTiO3, and the catalytic efficiency of composites is related to the content of Au. More importantly, the Au–SrTiO3 nanocomposites exhibit much higher photocatalytic activity under simulated sunlight than under visible light. In addition, a possible promotion mechanism of Au nanoparticles on the photocatalytic activity of SrTiO3 was proposed.
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published : vol. 126, no.5, May 2018
Kunyong KANG, Kaimeng XU, Gang ZHU, Can LIU, Yuanbo HUANG, Xiaoqing YANG, Zhenguan TANG and Zhifeng ZHENG
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This study investigates the influence of GeO2 on the nonlinear coefficient (α) and breakdown voltage (EB) of TiO2–Ta2O5–CaCO3 varistor ceramics doped with GeO2 and prepared according to a conventional ball milling–molding–sintering process. The electrical performance parameters, including the nonlinear coefficient (α), breakdown electric field (EB), and leakage current (JL), were assessed using a varistor direct-current instrument. The average barrier height ΦB of each sample was calculated using the relevant formula. Analyses conducted by X-ray diffraction, scanning electron microscopy, and scanning transmission electron microscopy demonstrated that GeO2 doping changed the microstructures of TiO2–Ta2O5–CaCO3 ceramics, resulting increased α and decreased EB values. Ceramics doped with 0.2 mol % Ta2O5, 0.2 mol % CaCO3 and 0.9 mol % GeO2 exhibited the maximum α value (α = 9.8) and the highest grain boundary barrier (ΦB = 0.92 eV) but a low EB value (EB = 17.2 V·mm−1).
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published : vol. 126, no.5, May 2018
Mitsuhiro HONDA, Qiyan ZHANG, Hiroki TATEYAMA and Yo ICHIKAWA
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The room temperature growth of ZnO nanoneedle arrays on seed layers was demonstrated via wet-chemical synthesis. The orientation of ZnO nanoneedles was found to be extremely high on the flat seed layer with high crystallinity, whereas a poor orientation was observed on rough seed layers. We expect that the direction of ZnO [0001] (c-axis) dictates the orientation of ZnO nanoneedles. With longer reaction time, ZnO nanoneedles grew dominantly in a length compared to a diameter. Dense ZnO nanoneedles with a high orientation is believed to be promising for many applications in optelectronics and photonics.
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published : vol. 126, no.5, May 2018
Li BAO, Xiwei QI, Ruibin MEI and Xiaohui CHEN
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Calcium doped bismuth ferrite (BiFeO3, BFO)-barium titanate (BaTiO3, BTO) powders were successfully synthesized by a facile sol–gel route. Subsequently as-synthesized powders were packed within a fugitive silver metal tube and formed into tapes with uniform thickness by means of cold drawing and rolling processes, which is called powder in tube (PIT) method. The influence of calcining temperature on the crystalline structure and characterization of BFO-based tape was also studied. The particle size of tape prepared by PIT method is becoming smaller, indicating PIT method has great effect on refined particle. Furthermore, the remanent magnetization 2Mr and coercive force Hc for the tape are 0.092 emu/g and 281.59Oe, respectively. The optimized calcining temperature for the tape is 400°C.
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published : vol. 126, no.5, May 2018
Tetsuro JIN, Tomoyo OCHIISHI, Yuri SHIBUYA and Tetsuo YAZAWA
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Hexagonal GdF3:Tm3+, which is thermodynamically unstable at room temperature, was successfully crystallized in borosilicate glass using a phase separation technique. The crystal structure of GdF3 was controlled by the addition of alkaline earth metals to the glass composition. Increasing the amount of SrF2 added to the glass composition to 1.65 mol % increased the amount of precipitation of hexagonal GdF3:Tm3+ crystals and the luminescence intensity. Lanthanide trifluoride phosphors were restrictively obtained in the borate phase as a result, and the emission of Tm3+ at 458 nm was observed. Furthermore, the luminescence intensity of GdF3:Tm3+ in the phase separation glass upon SrF2-doping was about three times larger than that without doping.
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published : vol. 126, no.5, May 2018
Mun Keun LEE and Shinhoo KANG
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Nano-sized ZnGa2O4, ZnGa2O4:Cr and ZnGa2O4:Ti phosphors were synthesized by low-temperature combustion method and the luminescent properties were studied in comparison with those from conventional solid-state reaction. The combustion reaction resulted in a single-phase spinel structure and the particles were 5–10 nm in size. Of all samples, undoped nano ZnGa2O4 exhibited an intrinsic blue emission and Ti-doped nano ZnGa2O4 had a tendency of white emission whereas Cr-doped nano ZnGa2O4 showed red emissions. Titanium ions in spinel structure was found to exist as in Ti3+ and Ti4+, but favouring trivalent state. The oxidation state of Cr ions was confirmed as 3+ in nano ZnGa2O4.
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published : vol. 126, no.5, May 2018
Kazuki MATSUZAWA, Masashi SHINSUGI, Daiki ATARASHI and Etsuo SAKAI
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Low heat Portland cement (LHC) containing expansive additives can reduce the temperature stress and the crack generation of concrete, therefore it can be used for producing mass concrete and high-strength concrete. However, since LHC does not contain much aluminum, it is difficult for LHC to immobilize chloride ions and be used in salt damage environments such as seashore. CaO·2Al2O3 addition to LHC can be the countermeasure, however chloride immobilization in LHC with CaO·2Al2O3 has not been researched in detail. This paper describes the influence of CaCl2 addition on hydration of LHC containing an expansive additive and CaO·2Al2O3. In LHC containing an expansive additive, ettringite was mainly generated with and without CaCl2. In contrast, in LHC containing an expansive additive and CaO·2Al2O3, monosulfate was generated without CaCl2, and Friedel’s salt were generated with CaCl2. Therefore, LHC containing an expansive additive and CaO·2Al2O3 showed potential for chloride ion immobilization.
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published : vol. 126, no.5, May 2018
Hiroki YAMASHITA, Takaaki OGAMI and Kiyoshi KANAMURA
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Pt–Rh/CeO2/Al2O3 was successfully synthesized by the hydrothermal method, and its chemical and physical properties as well as its catalytic activity were evaluated. Pt–Rh/CeO2/Al2O3 was also synthesized by the conventional impregnation method for purpose of comparison. Pt–Rh/CeO2/Al2O3 synthesized by the hydrothermal method comprised hollow CeO2 nanorods coated with nanoparticle arrays that served as selective supports for Pt and Rh on CeO2 surfaces. Although the lights-off temperatures of NO and C3H6 were similar for Pt–Rh/CeO2/Al2O3 catalysts synthesized by the two methods, moreover, Pt–Rh/CeO2/Al2O3 synthesized by the hydrothermal method exhibited a lower lights-off CO temperature than that synthesized by the impregnation method. Pt–Rh/CeO2/Al2O3 synthesized by the hydrothermal method also exhibited better catalytic activity, which was attributed to its better dispersion of Pt and Rh than that synthesized by the impregnation method.
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published : vol. 126, no.5, May 2018
Kenji OBATA, Akane DOI, Maiko NISHIBORI, Kengo SHIMANOE, Takuya SUZUKI and Shigenori MATSUSHIMA
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La-added and pure MgFe2O4 powders were prepared from a malic acid complex, and the effect of La-adding on the microstructure and specific surface area of MgFe2O4 powder were examined. There were no traces of impurity phases for pure MgFe2O4 powder in the X-ray diffraction measurement after calcination in the range of 600 to 800°C. When La atoms were added to MgFe2O4, the crystallite growth of MgFe2O4 was suppressed remarkably, resulting in a higher specific surface area in comparison with the pure material, and the lattice volume increased. X-ray photoelectron spectroscopy measurements showed that the binding energies of Mg 2s, Fe 2p, O 1s, and La 3d signals were in good agreement with the Mg2+, Fe3+, O2−, and La3+ valence states, respectively. Scanning electron microscopy observations revealed that MgFe2O4 powder shows an aggregation of granular particles and that the individual particles are tightly interconnected with each other, whereas smaller particles compared with pure MgFe2O4 were observed for the La-added powder. It was found from the N2 adsorption measurement, moreover, that the amount of mesopore increases with La addition.
Note
published : vol. 126, no.5, May 2018
Keiji KUSUMOTO
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Glass mixtures based on turquoise blue glaze were synthesized by the conventional ceramic method, and their color properties were investigated as environmentally friendly Co-free inorganic blue pigments. Samples showed coloring from light blue to black depending on their compositions. The bluest color was observed for 0.60 BaO·0.20 Li2O·0.20 Na2O·0.45 Al2O3·2.50 SiO2 in a 20 wt % CuO sample heated at 900°C, which had the following color parameters: (L*a*b*) of L* = 41.9, a* = −4.5, and b* = −14.2. The a*, b* values are comparable to those of commercial Co-based blue pigments. Since the glass mixtures do not include cobalt oxide as a raw material, it should be an attractive alternative to conventional Co-based inorganic blue pigments.
Express Letter
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Miyuri TERASAWA, Tsuyoshi HONMA, Takayuki KOMATSU
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Optically transparent and electrically conductive glass-ceramics have been successfully prepared from 1Na2O–0.5MnO–0.5FeO–1SiO2 (Na2Mn0.5Fe0.5SiO4) glass by heat-treatment. Crystallization tendency was sensitive to the valence state of transition metal oxide. The as-quenched glass melted at 1400°C for 15 min, exhibited two exothermic peaks in the differential thermal analysis. Optically transparent glass-ceramics obtained at 493°C for 3 h showed simple X-ray diffraction pattern, which could be assigned to a cubic phase with a lattice constant of 0.74511 nm. A monoclinic Na2MSiO4 (M = Mn, Fe) phase appeared with the heat treatment above 610°C, suggesting that the crystal phase precipitated in the low temperature region was thermodynamically metastable. The transparent glass-ceramics showed an order of magnitude higher electrical conductivity than that of glass and the monoclinic phase.