Lithium–lanthanum silicate oxyapatite exhibits high lithium-ion conductivity at temperatures above 400 °C. To further enhance its ionic conductivity, the relationships among the microstructure, bulk conductivity, and grain boundary conductivity were investigated for Li-rich compositions. Li_xLa_10−xSi₆O_27−x (x = 1–8), Li₅La₅Si₅O₂₀, Li₅La₅Si_4.5O₁₉, Li₆La₄Si_4.5O₁₈, and Li₇La₃Si₄O₁₆ were synthesized, and their ionic conductivities were determined. Using X-ray diffraction, Li₂La₈Si₆O₂₅, Li₅La₅Si₅O₂₀, Li₅La₅Si_4.5O₁₉, Li₆La₄Si_4.5O₁₈, and Li₇La₃Si₄O₁₆ were analyzed to be close to the apatite phase with few impurities. Scanning electron microscopy/energy-dispersive X-ray spectroscopy and nuclear magnetic resonance analyses revealed that the lithium–silicate glass phase increases with respect to the apatite phase in the following order: Li₂La₈Si₆O₂₅ < Li₅La₅Si₅O₂₀ < Li₅La₅Si_4.5O₁₉ < Li₆La₄Si_4.5O₁₈ < Li₇La₃Si₄O₁₆. Further, as the La/Si ratio of the apatite phase increases, the chemical composition changes from Li₁La₉Si₆O₂₆ to Li₃La₇Si₆O₂₄. Both the bulk (apatite phase) and the grain boundary (glass phase) resistivities at 400 °C decreased in the order Li₅La₅Si₅O₂₀ > Li₅La₅Si_4.5O₁₉ > Li₆La₄Si_4.5O₁₈ > Li₇La₃Si₄O₁₆. The apparent activation energies for the bulk ion conductivity of Li₅La₅Si₅O₂₀, Li₅La₅Si_4.5O₁₉, Li₆La₄Si_4.5O₁₈, and Li₇La₃Si₄O₁₆ were 57.3, 47.6, 43.0, and 40.4 kJ mol⁻¹, respectively. The total conductivities (bulk + grain boundary conductivities) of Li₇La₃Si₄O₁₆ (8.1 × 10⁻³ S cm⁻¹ at 400 °C) was approximately four times higher than that of Li_1.08LaSiO_4.04 (2.2 × 10⁻³ S cm⁻¹ at 400 °C), which has been previously reported to have the highest ionic conductivity.

Shrinkage-rate controlled flash (SCF) sintering using alternative current electric field was systematically performed for 3–10 mol % Y₂O₃-doped ZrO₂. As results, the uniformly densified compacts with about 99 % relative densities could be produced at furnace temperatures of about 754–781 °C for about 30 min as SCF-regime irrespective of Y concentration, while the achieved densities were limited by conventional flash sintering. The shrinkage-rates during SCF-sintering were found to be enhanced in lower temperature range comparing those during thermal-sintering. The enhancement of shrinkage-rates in lower temperature range observed in SCF-sintering is possibly related to the reduction of apparent activation energy of sintering under electric fields.

To obtain guidelines for the microstructure design of BaTiO₃-based multilayer ceramic capacitors from the viewpoint of polarization behavior, the effects of AC- and Uni-poling treatments were examined using intentionally grain-growth samples. For purposes of comparison, the DC-aging characteristics of each sample were also examined. From the results of the polarization behavior induced by AC- and Uni-poling treatments, it was confirmed that changes in the core–shell structure, grain size, and oxygen vacancy concentration of the dielectrics strongly affected the domain wall pinning. In comparison with DC-aging characteristics, AC- and Uni-poling treatments are also expected to be effective tools for clarifying the relationships among more detailed microstructure and polarization behaviors of dielectrics.

In order to obtain material design guidelines for next-generation multilayer ceramic capacitors (MLCCs) from the viewpoint of polarization behavior, we investigated the changes in polarization behavior with AC- and Uni-poling treatment using (Ba,Ca)(Ti,Zr)O₃-based MLCC samples in which a part of the BaTiO₃ in the core was modified with Ca and Zr. Comparisons with DC-aging measurements confirmed that the AC- and Uni-poling treated samples clearly showed a unique phenomenon in which the domain wall of the (Ba,Ca)(Ti,Zr)O₃-based core phase moves faster than that of the BaTiO₃-based core phase. AC- and Uni-poling treatments are expected to be useful tools for evaluating the relationship between more detailed microstructure and polarization behavior of dielectric materials.

A first-principles energy band calculation was performed for V-doped ZrO₂, (M,V)-doped ZrO₂ (M = Al, Y, La) supercells, and pure ZrO₂ unit cells to elucidate the effects of M doping on the electronic structure and optical properties of a V-doped ZrO₂ pigment. Structural optimization calculations revealed that the calculated lattice constants of ZrO₂ agreed well with those obtained from experimental data. Using a generalized gradient approximation calculation, the minimum bandgap was estimated to be 3.67 eV. Density of states calculations indicated that the valence band (VB) was mainly composed of O 2p states mixed with Zr 4d states. The conduction band (CB) was mainly composed of Zr 4d states with small O 2p character. For V-doped ZrO₂, three minority-spin and four majority-spin localized states newly appeared in the bulk ZrO₂ bandgap. They were mainly derived from V 3d states. The addition of a second element, M, to V-doped ZrO₂ changed the energy position and peak number of the localized V 3d states in the bandgap. This change was most pronounced for La, which has the largest ionic radius of all M. Based on the dielectric function calculation of the V-doped ZrO₂ supercell, there was a broad absorption from the O 2p VB states to the V 3d gap states occurring from the ligand–metal charge transfer (LMCT) and dd transition of V⁴⁺ ions, as well as a VB–CB optical transition in the ZrO₂ bulk. Furthermore, when an M atom was added to the V-doped ZrO₂ supercell, the optical absorption by the LMCT was considerably enhanced in the visible region. Based on these calculations, which supplement the research on common inorganic dyes, we conclude that the addition of a second element, M, is effective in enhancing the chromogenicity of the Zr-yellow pigment.

In the vitrification of high-level radioactive waste, it is important to understand the crystallization behavior because precipitation of molybdenum (Mo) phase reduces the chemical durability of the waste form. In this study, the crystallization of Mo phase under slow cooling conditions was investigated with glasses of SiO₂–B₂O₃–Al₂O₃–CaO–Na₂O–MoO₃ systems and simulated high-level waste (HLW) compositions. When the B₂O₃ in the glass decreases and the Al₂O₃ increases, the phase separation of Na₂MoO₄ and the crystallization of powellite (CaMoO₄) were promoted. The waste components included in the HLW glass has the effect of increasing the MoO₃ solubility and suppressing crystallization. Furthermore, it was found that the suppressing effect was further enhanced by addition of rare earth element oxides. In contrast, there was no suppressing effect of addition of V₂O₅ on the crystallization of powellite. The precipitation of the Na₂MoO₄ is mainly related to liquid-liquid immiscibility, while the crystallization of powellite depends on the multiple factors, an equilibrium MoO₃ solubility at high temperature, nucleation and growth rates under slow-cooling and crystallization of Ca-silicate phase. The compositional effects on the crystallization can be described using the melt viscosity.

In this study, silicon carbide (SiC) nanoplates are prepared from the waste quart tube (main composition: silicon dioxide) and waste autoclave lining (main composition: polytetrafluoroethylene) produced in the laboratory. The reaction is carried in a stainless steel autoclave at 600 °C through a magnesium reduction route. Electron microscopy investigations show that the nanoplate thickness of the SiC sample is about 20 nm, and the edge length is about 200 nm. Furthermore, the photoluminescence property of the obtained SiC nanoplates is investigated.

The magnetic hybrid structure of a half-metallic ferromagnetic oxide and a non-magnetic oxide is promising for future spintronic devices. However, the ferromagnetic layer’s structural and magnetic characterizations must be improved urgently. Here, we report on the effect of annealing time on enhancing the structural and magnetic properties of Fe₃O₄ films. Radio-frequency magnetron sputtering was used to fabricate Fe₃O₄ thin films on a multilayer of MgO/Ta/SiO₂ at room temperature. As-grown Fe₃O₄ samples were annealed at the optimal temperature for various times. The structural and magnetic properties of Fe₃O₄ were observed by using atomic force microscopy, X-ray diffraction, and a vibrating sample magnetometer. The structural characterization of Fe₃O₄ thin films is significantly enhanced when increasing the annealing time. Moreover, the magnetization of Fe₃O₄ thin films is also highly improved compared to the bulk value. Our finding provides a highlight for the next generation of spintronics.