Ceramic Society of Japan Acta Medica Okayama 1348-6535 134 7 2026 Dielectric response modulation in relaxor (Sr,Ba)Nb2O6 via engineered defect 455 460 EN Ryusei Shiota Graduate School of Natural Science and Technology, Okayama University Takashi Teranishi Graduate School of Natural Science and Technology, Okayama University Shinya Kondo Department of Energy Engineering, Nagoya University Akira Kishimoto Graduate School of Natural Science and Technology, Okayama University Defect engineering provides an effective pathway to tune the dielectric response of relaxor ferroelectrics, yet the roles of individual defect species in tungsten bronze (TTB) systems remain unclear. Here, we investigated how engineered Ti–VO•• defect dipoles and native oxygen vacancies introduced through reduction annealing modify the dielectric properties of relaxor (Sr0.5,Ba0.5)Nb2O6 (0.5-SBN). Ti loading forms stable defect dipoles that generate smaller polar nanoregions (PNRs), suppress their overgrowth, and increase the number of dynamically active PNRs at room temperature, leading to enhanced permittivity ƒĆŒ while preserving DC-bias stability and breakdown strength (EB). Reduction annealing generates Nb4+-related local polarizations aligned with the external electric field, which strengthen dipole fluctuations and slightly increase ƒĆŒ. Electron localization further relaxes the TTB-A2 site disorder–induced random fields, yielding a sharper dielectric peak and promoting more uniform PNR growth. Microwave dielectric spectroscopy combined with electromagnetic simulations revealed that the increases in ƒĆŒ for both Ti-loaded and reduced samples (0.5-SBNT and Reduced 0.5-SBN, respectively) originate predominantly from enhanced dipole polarization. Despite grain coarsening in 0.5-SBNT, the EB remained unchanged, indicating that defect dipoles act as pinning centers that inhibit field-induced PNR aggregation. In reduced 0.5-SBN, EB increased up to pO0 = 4.3 ~ 10|3 atm owing to relaxed random fields, whereas excessive reduction reduced EB through carrier-driven space-charge effects. These results demonstrate that precise control of defect species enables simultaneous optimization of ƒĆŒ, DC-bias stability, and EB in TTB-type relaxor ferroelectrics. No potential conflict of interest relevant to this article was reported.

Elsevier BV Acta Medica Okayama 2238-7854 42 2026 An electric field temporarily strengthens zirconia ceramics 1806 1810 EN Akira Kishimoto Faculty of Environmental, Life, Natural Science and Technology, Okayama University Takahiro Shimizu Faculty of Environmental, Life, Natural Science and Technology, Okayama University Mitsuru Nishiyama Faculty of Environmental, Life, Natural Science and Technology, Okayama University Shinya Kondo Faculty of Environmental, Life, Natural Science and Technology, Okayama University Takashi Teranishi Faculty of Environmental, Life, Natural Science and Technology, Okayama University By applying an electric field to yttria-stabilized zirconia (8YSZ) equipped with an inert electrode, oxide ions are localized near the positive electrode, causing it to expand. When polarization was performed under different conditions, it was possible to strengthen the material to 1.5 times that of an untreated sample. The lattice constant of the positive electrode surface after polarization was larger than before polarization. When the Vickers hardness of the positive electrode surface was measured by changing the test load, the smaller the load, the higher the hardness value. Polarization caused oxide ions to move near the positive electrode, filling in the defects and generating an expanded layer with a large lattice constant. It is believed that this was subjected to compressive stress from the bulk layer, which had not changed in volume, resulting in an increase in strength. No potential conflict of interest relevant to this article was reported.

ˆź”ŹŽŠ’c–@l•²‘Ģ•²–––č‹ą‹¦‰ļ Acta Medica Okayama 0532-8799 73 3 2026 ”MŠŌĆ…ˆ³‰Įˆ³–@‚š—p‚¢‚½ƒCƒbƒgƒŠƒAˆĄ’艻ƒWƒ‹ƒRƒjƒAćk–§‘w‚Ģ’į‰·Œ`¬ 55 59 EN Kyohei MANABE Osaka Gas Co. Ltd. Mitsuaki ECHIGO Osaka Gas Co. Ltd. Akira KISHIMOTO Institute of Academic and Research, Faculty of Environmental, Life, Natural Science and Technology, Okayama University The sintering conditions using hot isostatic press (HIP) of yttria-stabilized zirconia (YSZ) were investigated to obtain a dense YSZ layer at low sintering temperature such as 1000‹C for an electrolyte of metal-supported solid oxide fuel cell. It was found that a dense YSZ pellet with relative density of 93% could be obtained under a sintering condition of 1000‹C-10 hours with HIP in 195 MPa. On the other hand, in X-ray diffraction analysis of the dense YSZ pellet, peaks of the monoclinic phase were slightly detected in addition to peaks of the cubic phase. From energy dispersive X-ray spectroscopy analysis, a small amount of boron was detected in the dense YSZ pellet. It is considered that the YSZ crystalline phase transformation of cubic to monoclinic phase was occurred by the boron diffusion from the diffusion barrier coating of metal foil capsule used for the HIP. No potential conflict of interest relevant to this article was reported.

American Chemical Society (ACS) Acta Medica Okayama 2574-0962 2025 Enhanced Charge-Transfer Kinetics Enabled by ZrO2–Based Dielectric Layers in Lithium-Ion Batteries EN Takashi Teranishi Graduate School of Natural Science and Technology, Okayama University Yusuke Higaki Graduate School of Natural Science and Technology, Okayama University Tomonori Imamura Graduate School of Natural Science and Technology, Okayama University Motoki Horibe Department of Advanced Ceramics, Nagoya Institute of Technology Shinya Kondo Department of Energy Engineering, Nagoya University Chinatsu Sasaoka R&D Laboratory, Nippon Denko Co., Ltd. Hikaru Hirabaru R&D Laboratory, Nippon Denko Co., Ltd. Shingo Katayama R&D Laboratory, Nippon Denko Co., Ltd. Masanobu Nakayama Department of Advanced Ceramics, Nagoya Institute of Technology Akira Kishimoto Graduate School of Natural Science and Technology, Okayama University The development of high-rate capability lithium-ion batteries (LIBs) requires suppression of charge-transfer resistance (RCT) at electrode–electrolyte interfaces. Here, zirconia-based dielectric oxides (MZ; M = Y, Gd, Sm, Er, etc.) were introduced onto LiCoO2 (LCO) surfaces as electronically and ionically insulating modifiers to accelerate interfacial ion transport. Electrochemical impedance spectroscopy showed that Y2O3 modified ZrO2 (YZ) decoration reduced RCT from 75.8 ƒ¶ in reference LCO to 38.3 ƒ¶, accompanied by a 2.3-fold improvement in capacity retention at 20C. Density functional theory molecular dynamics (DFT–MD) simulations showed that solvated Li ions coordinate with surface oxygen atoms in discharging, and that adsorption energies are governed by local charge distributions determined by stabilizing cations. Optimal adsorption activity, and thus the lowest RCT, occurred when the surface charge corrugation was balanced. These findings provide design principles for dielectric interface engineering to enhance rate capability of LIBs. No potential conflict of interest relevant to this article was reported.

AIP Publishing Acta Medica Okayama 0003-6951 126 1 2025 Dynamic domain motion enhancing electro-optic performance in ferroelectric films 012901 EN Shinya Kondo Graduate School of Environmental, Life, Natural Science and Technology, Okayama University Kazuki Okamoto Department of Energy Engineering, Nagoya University Osami Sakata Japan Synchrotron Radiation Research Institute (JASRI) Takashi Teranishi Graduate School of Environmental, Life, Natural Science and Technology, Okayama University Akira Kishimoto Graduate School of Environmental, Life, Natural Science and Technology, Okayama University Takanori Nagasaki Department of Energy Engineering, Nagoya University Tomoaki Yamada Department of Energy Engineering, Nagoya University With the rapid advancement of information technology, there is a pressing need to develop ultracompact and energy-efficient thin-film-based electro-optic (EO) devices. A high EO coefficient in ferroelectric materials is crucial. However, substrate clamping can positively or negatively influence various physical properties, including the EO response of these films, thus complicating the development of next-generation thin-film-based devices. This study demonstrates that reversible dynamic domain motion, achieved through substrate clamping, significantly enhances the EO coefficient in epitaxial ferroelectric rhombohedral Pb(Zr, Ti)O3 thin films, where the (111) and (⁠ 111⁠) domains coexist with distinct optical axes. In principle, this approach can be applied to different film-substrate systems, thereby contributing to the advancement of sophisticated EO devices based on ferroelectrics. No potential conflict of interest relevant to this article was reported.

MDPI Acta Medica Okayama 2079-4991 14 20 2024 Colossal Dielectric Constant of Nanocrystalline/Amorphous Homo-Composite BaTiO3 Films Deposited via Pulsed Laser Deposition Technique 1677 EN Shinya Kondo Graduate School of Environmental, Life, Natural Science and Technology, Okayama University Taichi Murakami Graduate School of Environmental, Life, Natural Science and Technology, Okayama University Loick Pichon Institut National de la Recherche Scientifique (INRS), Centre Énergie, Matériaux et Télécommunications Joel Leblanc-Lavoie Institut National de la Recherche Scientifique (INRS), Centre Énergie, Matériaux et Télécommunications Takashi Teranishi Graduate School of Environmental, Life, Natural Science and Technology, Okayama University Akira Kishimoto Graduate School of Environmental, Life, Natural Science and Technology, Okayama University Khakani, My Ali El Khakani Institut National de la Recherche Scientifique (INRS), Centre Énergie, Matériaux et Télécommunications We report the pulsed laser deposition (PLD) of nanocrystalline/amorphous homo-composite BaTiO3 (BTO) films exhibiting an unprecedented combination of a colossal dielectric constant (epsilon(r)) and extremely low dielectric loss (tan delta). By varying the substrate deposition temperature (T-d) over a wide range (300-800 degrees C), we identified T-d = 550 degrees C as the optimal temperature for growing BTO films with an epsilon(r) as high as similar to 3060 and a tan delta as low as 0.04 (at 20 kHz). High-resolution transmission electron microscopy revealed that the PLD-BTO films consist of BTO nanocrystals (similar to 20-30 nm size) embedded within an otherwise amorphous BTO matrix. The impressive dielectric behavior is attributed to the combination of highly crystallized small BTO nanograins, which amplify interfacial polarization, and the surrounding amorphous matrix, which effectively isolates the nanograins from charge carrier transport. Our findings could facilitate the development of next-generation integrated dielectric devices. No potential conflict of interest relevant to this article was reported.

Elsevier Science B.V. Acta Medica Okayama 0167-577X 65 14 2011 Effect of varying the ratio of matrix/dispersoid particle size on the piezoresistivity of alumina/carbon-black composite ceramics 2197 2200 EN Akira Kishimoto Yuto Takagawa Takashi Teranishi Hidetaka Hayashi Alumina/carbon-black composite ceramics with different percolation thresholds were fabricated by changing the size ratio of constituent particles. The dependence of resistivity on pressure was established for each sample. The compositional dependence of resistivity can be explained by percolation theory. The percolation threshold decreases with increasing alumina/carbon-black particle size ratio. The pressure dependence of the resistivity increases as the composition approaches the percolation threshold. When the relative composition at the percolation threshold is fixed, the sensitivity increases with increasing matrix/dispersoid initial particle size ratio. No potential conflict of interest relevant to this article was reported.

Elsevier Science Ltd Acta Medica Okayama 0272-8842 34 4 2008 Improvement of piezoresistance properties of silicon carbide ceramics through co-doping of aluminum nitride and nitrogen 845 848 EN Akira Kishimoto Yasuyuki Okada Hidetaka Hayashi The piezoresistance coefficient was measured on co-doped silicon carbide ceramics. Evaluation samples of alpha-silicon carbide ceramics were first fabricated by glass capsule HIP method using powder mixture of silicon carbide and aluminum nitride with various ratios. The resultant aluminum nitride added silicon carbide ceramics were doped with nitrogen by changing the post-HIP nitrogen gas pressure. The lattice parameter increased with the amount of adding aluminum nitride indicating that the incorporated aluminum substituted smaller silicon atoms. After post-HIP treatment, lattice parameter then decreased with nitrogen gas pressure. The piezoresistive coefficient increased with the addition of aluminum nitride, it further increased with the nitrogen doping pressure. No potential conflict of interest relevant to this article was reported.