Journal of the Ceramic Society of Japan
vol. 134, no.8, 2026
◆Full paper◆
Thermodynamics of W-type ferrite solid-solution system SrCoxFe18−xO27
https://doi.org/10.2109/jcersj2.26038
Shinji Nakai, Takeshi Waki, Yoshikazu Tabata, Hiroto Ohta, Masaki Kato, Christian Teichmann, Jörg Töpfer and Hiroyuki Nakamura
543
W-type ferrite (AT2+2Fe3+16O27, A = Sr, Ba, etc., T2+ = Fe2+, Co2+, Zn2+, etc.) is a type of hexagonal ferrite with different magnetic properties depending on T2+. It is a promising functional material for various applications. However, its phase stability, particularly when T2+ is partially or fully a stable divalent cation such as Co2+, is not well understood from an equilibrium perspective. We performed thermogravimetry (TG) measurements, compositional analyses, as well as high oxygen pressure (PO2) synthesis, to estimate the equilibrium PO2 of the reduction reaction of the W-type ferrite solid-solution system, SrCoxFe18−xO27. Furthermore, we thermodynamically evaluated the behavior of the equilibrium PO2 versus Co concentration in the W phase. Our results show that the equilibrium PO2 of the solid-solution W, SrCoxFe18−xO27, diverges as the composition approaches SrCo2Fe16O27 because the configuration entropy change associated with Fe2+ formation in the W phase diverges as Fe2+ vanishes.
◆Express letter◆
Bond angle distributions in silica polymorphs
https://doi.org/10.2109/jcersj2.26055
Shinji Kohara, Yohei Onodera, Motoki Shiga, Hirokazu Masai, Atsunobu Masuno, Koji Kimura and Koichi Hayashi
555
Bond angle distributions (BADs) in silica crystals, silica glass, and siliceous zeolites were compared to understand the topology of silica polymorphs. It is found that the Si–O–Si bond angle is 180° in β-cristobalite, which is characteristic of highly symmetrical sixfold rings. In contrast, the Si–O–Si BAD of silica glass, obtained from a molecular dynamics–reverse Monte Carlo model, has an average value of 153° with a full width at half maximum (FWHM) of 20°. The Si–Si–Si BAD of β-cristobalite exhibits a peak at 110° demonstrates that SiSi4 hyper tetrahedra possess high symmetry. This feature is consistent with the presence of symmetric six-membered rings in β-cristobalite. On the other hand, both coesite and silicalite-1 (MFI) shows a variety of bond angles like silica glass, which is consistent with the variation of (Si–O)n ring size.
◆Special Article-Academic Achievements◆
The 80th CerSJ Awards for Academic Achievements in Ceramic Science and Technology: Review
New phosphor exploration from single particle and local structure
https://doi.org/10.2109/jcersj2.26042
Takashi Takeda
559
Ceramics phosphors with luminescent centers are composed of luminescent center ions and host materials that accommodate these centers. In this paper, three topics for new phosphor exploration are presented. (1) new phosphor exploration focusing on individual phosphor particles within powder products for the discovery of new material phosphors, (2) new phosphor with unique luminescent centers different from the conventional substitutional type, and (3) new phosphor exploration utilizing local structure similarity to achieve desired luminescent properties.
◆Special Article-Advancements◆
The 80th CerSJ Awards for Advancements in Ceramic Science and Technology: Review
Strain engineering in lead zirconate titanate thin films: Reversible ferroelastic domain switching and giant electromechanical response
https://doi.org/10.2109/jcersj2.26040
Yoshitaka Ehara
565
Piezoelectric thin films are essential building blocks for next-generation microelectromechanical systems (MEMS). However, their functional performance has historically been limited by substrate mechanical constraints—a phenomenon known as the “clamping effect.” This phenomenon typically suppresses ferroelectric- and ferroelastic-domain mobilities. This review summarizes a paradigm shift in thin-film design: it redefines substrate clamping as a vital “restoring force” that ensures reversible domain switching rather than viewing it as purely degradative. By implementing a “hybrid strain engineering” approach that precisely tunes epitaxial and thermal strains in lead zirconate titanate thin films, our group demonstrates the feasibility of maximizing extrinsic contributions from non-180° (ferroelastic) domain-wall motion. Employing in situ synchrotron X-ray diffraction (XRD) at SPring-8, our group provides direct evidence of ultrafast, reversible 90°-domain switching at megahertz frequencies. This design guideline enables the giant piezoelectric responses in MEMS cantilevers, outperforming conventional clamped films and providing a scalable path for Beyond 5G/6G communication technologies and high-efficiency actuators.
◆Full papers◆
Substitution effect of metal oxide on the elastic modulus of aluminoborate glasses
https://doi.org/10.2109/jcersj2.26044
Hirokazu Masai
576
The remarkable diversity of the physical properties of glass is primarily attributed to its ability to incorporate various chemical species. Glass is a solidified liquid, i.e., a monolithic material with a “randomly” connected network; therefore, its properties can be tailored through compositional design. Titanium dioxide (TiO2), which is classified as an intermediate oxide, affects the structural, thermal, optical, and mechanical properties of glass. Moreover, the valence of titanium influences the optical properties of glass and its thermal stability against the precipitation of crystallites. This study investigates the substitution effect of TiO2 on aluminoborate glasses with high hardness and Young’s modulus. The glasses are prepared using a conventional melt-quenching method. Ti-free glasses possess high transparency in the visible region, and the coefficient of thermal expansion correlates with those of the substituted metal oxides. Both the thermal stability against crystallization and the mechanical properties change with composition. Although structural data for B2O3 and Al2O3 in all glasses are not available, the elastic properties may mainly depend on the dissociation energies of the metal oxides.
Degradation of 2-naphthol and antiviral activities of Bi2Sn2O7 doped with La or Ce under dark and visible-light conditions
https://doi.org/10.2109/jcersj2.26039
Riku Nakane, Yasuhide Mochizuki, Toshihiro Isobe, Keiichi Kobayashi, Takeshi Nagai, Hitoshi Ishiguro and Akira Nakajima
586
La- or Ce-substituted Bi2Sn2O7 (BSO) powders were synthesized via a hydrothermal method, and correlations between their structural, compositional, and adsorption properties and their 2-naphthol decomposition and antiviral activities under dark and visible-light conditions were investigated. Ten mol % of Bi was substituted with La or Ce, and all samples were confirmed to be single-phase BSO, exhibiting lattice parameter changes consistent with the ionic radii of the dopant ions. All samples were found to decompose 2-naphthol in aqueous solution at room temperature even in the dark, and the activity was further enhanced under visible-light irradiation. Antiviral performance was evaluated against two structurally distinct viruses, a non-enveloped virus and an enveloped virus, using test procedures with reference to ISO methods. Visible-light irradiation enhanced the antiviral activity of all samples, with La-substituted BSO exhibiting the highest performance against both viruses under both dark and visible-light conditions. The observed antiviral activity is attributed primarily to interactions between rare-earth elements and viral proteins, leading to virus immobilization on the material surface, followed by structural damage to viral components, including capsid disruption, envelope oxidation, and spike protein denaturation, driven by the intrinsic oxidative properties of BSO and the presence of rare-earth elements. It was suggested that La substitution is more effective than Ce substitution at promoting virus immobilization, resulting in superior antiviral activity.
◆Announcement◆
Call for a Guest Editor for a Special Issue
https://doi.org/10.2109/jcersj2.134.A8-1A8-1
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