To detect ionizing radiations efficiently, bulk phosphor materials, including single crystals, opaque and transparent ceramics, and glasses, have been used. Phosphors for ionizing radiation detection are classified into two groups such as scintillators and storage phosphors. In terms of the emission intensity, an inverse correlation of scintillation and storage luminescence has been confirmed in many materials. Based on such a relationship, many new phosphors for ionizing radiations have been developed, and some selected results are shown.

Highly efficient energy storage devices are essential for a sustainable society. Since the launch of lithium-ion batteries in 1991, optimization efforts over the past 30 years have significantly improved their performance, such as energy density, and they now occupy the largest share of the energy storage device market. However, LiCoO₂-based positive electrode materials face supply risks due to cobalt availability and have reached their performance limits, which inhibits further large-scale deployment. In this review, we summarize the recent progress in advanced positive electrode materials for lithium-ion batteries.

An interparticle photo-crosslinkable Pickering emulsion with a high transparency was prepared to improve the printing resolution of porous silica components when using the digital light processing (DLP) approach. A transparent photocurable Pickering emulsion was obtained by vigorously mixing a mixture of isopropyl myristate (IPM) and turpentine oil into a dimethyl sulfoxide aqueous suspension of silica particles in which small amounts of diacrylate monomers and photo-radical initiator were pre-dissolved. Pickering emulsions with a high linear transmittance were prepared by adjusting the refractive indices of the continuous and dispersed phases to be close to that of silica particles by adjusting the solvent mixing ratio. The effects of the in-line transmittance of the Pickering emulsions on the curing depth and overcuring behavior of the photocured bodies were evaluated. The improved in-line transmittance was found to help suppress light scattering during the photocuring process, resulting in a higher printing resolution compared with the use of opaque Pickering emulsions.

Negative thermal expansion materials are expected to be utilized for control of the thermal expansion of structure materials in the fields of semiconductor manufacturing, optical devices and precise machining where precise positioning is required. In this review, giant negative thermal expansions in PbVO₃ derivatives induced by ferroelctric-paraelectric transition and in modified BiNiO₃ induced by intermetallic charge transfer will be discussed.

Melilite-type silicate single crystals have emerged as promising materials for high-temperature piezoelectric applications in devices such as accelerometers, gas sensors, gas injectors, and pressure sensors. Sr-substituted Ca₂MgSi₂O₇ (Sr-CMS) single crystals were grown using the Czochralski (Cz) method. The Sr-CMS crystals exhibited no phase transition from room temperature to the melting temperature, with a piezoelectric d′₃₁ constant of 2.1 pC/N and a compressive strength of 830 MPa on a (ZXt)45° rotation-cut crystal substrate. Thus, Sr-CMS single crystals are promising for high-temperature pressure sensors. Ca₂Al₂SiO₇ (CAS) single crystals, which can also be grown using the Cz method, were investigated for high-temperature microbalance (MB) applications. They exhibit stable piezoelectric properties at high temperatures and have a lower density than langasite-type crystals. The thickness-shear vibration (d′₁₅ mode) of the CAS crystals was characterized, with the (XYw)45°-cut substrate showing the highest d′₁₅ constant. Using this crystal substrate, an LiZrO₃/Au/CAS device was configured and characterized as an MB. The device exhibited a resonance frequency shift when exposed to CO₂ gas in an air atmosphere at 500 °C, indicating that CAS single crystals can be used for MB applications at high temperatures.

This article briefly reviews the author’s recent studies on oxide-based amorphous functional materials, including amorphous and crystalline silica, silsesquioxane-based organic–inorganic hybrids, and the glass-ceramics of sodalites and boracites. The topics covered here are the development and spectroscopic characterization of these materials as well as processes to synthesize them. Major achievements are classified as the exploitation and environmental load reduction of synthesis processes, development and discovery of new materials/substances and phenomena, and evaluation of fundamental properties and values.

In recent, nano-CeO₂ has attracted attention as a new inorganic antiviral material. For this study, Gd-doped CeO₂ (CGO), known as a solid electrolyte, was prepared using hydrothermal method. Also, Cu was modified on the particle surface. Then the CGO antiviral activity was investigated in the dark and under visible light. With the obtained single-phase CGO, at least a part of the surface-modified Cu formed a solid solution. Antiviral activity tests were performed against bacteriophage Qβ, a non-enveloped virus, in accordance with ISO. Findings indicate that CGO exhibits antiviral activity against Qβ in the dark, and that it possesses high activity in an enzyme protein inactivation test, which is attributed to its peptide affinity, water repellency, and genome destruction ability derived from the element. The Cu modification effect on the antiviral activity in the dark was not clear. However, it was improved by Cu modification under visible light, which suggested a contribution by the photocatalytic reaction. These findings revealed Cu-modified CGO as a material that exhibits antiviral activity both in the dark and under visible light.