Language：English   Publisher：The Ceramic Society of Japan  

DOI： 10.2109/jcersj2.25171

CiNii Research

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DOI： 10.1021/acsaem.5c02963

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DOI： 10.1111/jace.70447

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/j.mseb.2025.118499

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DOI： 10.35848/1347-4065/ae0485

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IOP Publishing  

Abstract

The polarity of aluminum scandium nitride (Al_1-xSc_xN) thin films with different Sc contents deposited on transparent indium tin oxide (ITO) electrode-covered yttria-stabilized zirconia (YSZ) (111) substrates using radio frequency-magnetron sputtering was investigated. The Al_1-xSc_xN (x=0), i.e., pure AlN, film on ITO/YSZ(111) exhibited Al polar. By comparing with the polarity of AlN films deposited on different substrates, including Al₂O₃(0001), Pt/YSZ(111), YSZ(111), Pt(111)/TiO_y/SiO₂/Si(100) and Si(100), it was found that the polarity is affected by the degree of epitaxy. In addition, for the Al_1-xSc_xN films on ITO/YSZ(111), the transition from Al polar to N polar occurred with increasing Sc content, x, whereas the degree of epitaxy almost unchanged. These findings offer important insights into the mechanisms governing the self-poling in Al_1-xSc_xN thin films and pave the way for their use in electro-optic devices.

DOI： 10.35848/1347-4065/adf7b2

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Other Link： https://iopscience.iop.org/article/10.35848/1347-4065/adf7b2/pdf

Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Electrochemical Society  

One of important properties for Lithium-ion batteries is well known to be the rate performance because of the need to shorten discharging time and keep sufficient performance even under high load. The rate performance means the rate of decrease in charge-discharge capacity with increasing charge-discharge rate, which resulted from the internal resistance of batteries. Therefore, decreasing the internal resistance gives the improvement of the rate performance. The authors have thought to reduce the interfacial resistance between the electrolyte and cathode because it has been thought to be the largest of internal resistances. In order to reduce the interfacial resistance, we focused on an additive material adsorbing solvated Li-ions by the electrostatic force for cathode. Based on the possibility to design the positively and negatively polarized sites and their distance, fluorite-structured (Zr,M)O_2-xwas selected for the cathode additive. The fluorite-structured (Zr,M)O_2-x substituted with trivalent cation of M was synthesized for expecting the formation of negatively and positively polarized sites that adsorb solvated Li-ions and promote the dissolvation. It is thought that M³⁺ sites are negative as base sites δ^- and oxygen vacancy Vo sites are positive as acid sites δ⁺in (Zr⁴⁺ _1-2xM³⁺ _2x)O_2-xVo_x. Temperature-programmed desorption using acidic gas CO₂ and basic gas NH₃ revealed that many strong acidic and basic sites were formed, as compared with these of ZrO₂ without M-substitution. Furthermore, the synthesized (Zr,M)_O2-x powder was dispersed at 1 mass% on cathode particles of LMO, resulting in higher discharged capacity than those of LCO without additive and with ZrO₂ especially at high rates. Thus, we demonstrated that the design of negatively and positively polarized sites and their distance in the cathode additive (Zr,M)O_2-x was effective for improving the rate performance.



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DOI： 10.1149/ma2025-013216mtgabs

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Electrochemical Society  

The rate performance of Li-ion batteries is one of the important properties, especially for electric vehicles and power tools. The rate performance is governed by the internal resistance of a battery, which is mainly divided to electrode-resistance, electrolyte-resistance, and interfacial-resistance between electrolyte and electrode. Reducing these resistances can keep high charge-discharge capacity even at increasing charge-discharge rate, meaning the improvement of the rate performance. Among the resistances, the authors have tried to reduce the interfacial-resistance between electrolyte and cathode by using the cathode additive (Zr,M)O_2-x. The fluorite-structure of (Zr,M)O_2-xis one of candidates suitable for designing positively and negatively polarized sites that adsorb solvated Li-ions by the electrostatic force. The fluorite-structured (Zr,M)O_2-x substituted with trivalent cation of M was found to be effective in increasing the number and strength of positively and negatively polarized sites (acidic and basic sites), thereby improving the rate performance as a cathode additive. Assuming that M³⁺ sites are negative as base sites δ- and oxygen vacancy Vo sites are positive as acid sites δ⁺in (Zr⁴⁺ _1-2xM³⁺ _2x)O_2-xVo_x, it is thought that the kind of M³⁺ would affect the number and strength of negatively and positively polarized sites. Thus, we have investigated the effect of trivalent M³⁺ in cathode additive (Zr,M)O2_-x on rate performance of lithium batteries. Samples of (Zr⁴⁺ _1-2xM³⁺ _2x)O_2-xVo_x, where M=Sc, Y, La, Nd, Sm, Gd, Ho, Er, Yb, etc. and x=0.15, were prepared by a wet method. The experimental results of temperature-programmed desorption using acidic gas CO₂ and basic gas NH₃ revealed that the number and strength of acidic and basic sites corresponding to positively and negatively polarized sites, respectively, varied depending on M³⁺. Each (Zr,M)O_2-x powder was also dispersed at 1 mass% on cathode particles of LMO, showing the improvement of discharged capacity at high rates depending on M³⁺. The discharged capacity at high rates was found to have a tendency to become higher with increasing the number and strength of acidic and basic sites. This may result from differences in features of M such as ionic size, configuration of M³⁺ and Vo, electronegativity of M, and ligand-field stabilization energy of M³⁺.

DOI： 10.1149/ma2025-013382mtgabs

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AIP Publishing  

We investigated the dependence of the electro-optic (EO) properties of (111)-epitaxial Hf0.5Zr0.5O2 (HZO) thin films on their thickness in the range of 3–30 nm. HZO films were deposited on (La, Sr)MnO3-bufferred SrTiO3(001) substrates using pulsed laser deposition. Both the ferroelectric orthorhombic and paraelectric monoclinic phases were found to coexist in the 30 nm thick film, and the fraction of the former phase increased with the decrease in thickness down to 5 nm. Although the effective EO coefficient, reff, remained almost unchanged down to 10 nm and decreased with a further decrease in thickness, the evident EO response was observed down to 3 nm, which agrees with the fact that HZO films can maintain ferroelectric properties down to a few monolayers in thickness. The small reff in the HZO films with thickness below 5 nm was attributed to the stabilization of the ferroelectric rhombohedral-like phase.

DOI： 10.1063/5.0267559

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The electrocaloric effect (ECE)-induced temperature change (ΔT) in (Ba, Sr)TiO3-based ferroelectrics under unipolar electric fields was analyzed from the separate contributions of the dielectric constant (ε) and remanent polarization (Pr) based on the Maxwell relation. Consideration of the contributions of both ε and Pr is particularly important in a unipolar electric field operation, such as on/off field switching used in device applications. Direct ΔT measurements were also performed based on the lock-in thermography technique to verify the accuracy of the ΔT intensity estimated by the indirect method. The indirect and direct ΔT values were largely consistent. The ΔT intensity near the peak temperature of ΔT was dominated by the Pr contribution; a large ∂Pr/∂T was necessary to increase the overall ΔT magnitude. In contrast, a large ∂ε/∂T was essential to expand the operating temperature range of ΔT at temperatures higher than the dielectric maximum temperature. Quantitative understanding of the contributions of both ε and Pr to ΔT in unipolar electric fields is expected to guide the search for materials with a superior ECE.

DOI： 10.1063/5.0259805

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Powder and Powder Metallurgy  

DOI： 10.2497/jjspm.15f-t14-02

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Event date： 2025.6

Language：Japanese   Presentation type：Public lecture, seminar, tutorial, course, or other speech  

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Country：Japan  

Event date： 2025.9

Language：Japanese   Presentation type：Oral presentation (general)  

Country：Japan  

Event date： 2025.9

Language：Japanese   Presentation type：Oral presentation (general)  

Country：Japan