In solid oxide fuel cells (SOFCs), oxide ion conductors are suitable electrolytes to separate the fuel electrode from the air electrode, and their conductivity has room for improvement. We obtained high oxide ionic conductivity in La_9.7Si_5.7Mg_0.3O_26.25, an oxygen-rich apatite-type lanthanum silicate ceramic involving the partial substitution of Si with Mg in La_9.7Si₆O_26.55. Moreover, partial substitution of La with Sr yielded La_9.33Sr_0.37Si_5.7Mg_0.3O_26.065, which exhibited the highest bulk ionic conductivity (1.9 × 10⁻² S·cm⁻¹ at 500 °C), representing a 1.6-fold increase compared to La_9.7Si₆O_26.55 at 500 °C. To orient La_9.33Sr_0.37Si_5.7Mg_0.3O_26.065 in a magnetic field using a neodymium magnet with c-axis orientation, La was partially replaced by Nd, a trivalent rare earth element with magnetic properties, to prepare (La_0.8Nd_0.2)_9.33Sr_0.37Si_5.7Mg_0.3O_26.065, yielding c-axis oriented products. The ionic conductivity of the bulk parallel to the c-axis (σ//, 5.5 × 10⁻² S·cm⁻¹ at 500 °C) was 1.9 orders of magnitude higher than that of the bulk perpendicular to the c-axis (σ⊥) at 500 °C. An SOFC incorporating (La_0.8Nd_0.2)_9.33Sr_0.37Si_5.7Mg_0.3O_26.065 as the electrolyte [3 % H₂ (Ar balance) | Pt | Sm_0.2Ce_0.8O_1.9 | electrolyte | Sm_0.2Ce_0.8O_1.9 | Pt | air] was fabricated using a 1-mm thick c-axis oriented product. The maximum power outputs at 450, 500, and 550 °C were 29, 60, and 70 mW·cm⁻², respectively.

Efficient global optimization is crucial in resource-intensive computations, such as atomistic structure search using density functional theory (DFT) calculations. This has been accomplished by combining the DFT with Gaussian process regression within a genetic algorithm called GOFEE. In this work, we modified the GOFEE algorithm to increase its efficiency. We introduced the scaled lower confidence bound acquisition function, which balances the surrogate energy and uncertainty to improve the atomic structure exploration. We implemented similarity-based structure sharing between independent GOFEE calculations to avoid redundant calculations in the target potential. We applied our modifications to find the global minimum in two-dimensional Himmelblau’s function, various hydrocarbon molecules, C₆₀, TiO₂ anatase surface reconstructions, and bulk Co-doped TiO₂ anatase (Co@TiO₂). While our modifications successfully increased the success rate in finding the global minimum of the former systems, they failed to find the ferromagnetic structure of Co@TiO₂, as observed in experiments.

Layered perovskite compounds exhibit various electrical properties due to their crystal structure. This review focused on the synthesis and characterization of B-cation-deficient hexagonal perovskite A₃B₂O₉ (A = Ba, Sr; B = W, Re), which exhibits two-dimensional perovskite layers and perovskite layer stacking along the [111] direction in the simple perovskite notation. Ba₃W₂O₉, Sr₃W₂O₉, and Sr₃Re₂O₉ were obtained through high-pressure synthesis. Crystal structure analysis was conducted using single crystal X-ray diffraction and transmission electron microscopy. Ba₃W₂O₉ was found to be isostructural with Ba₃Re₂O₉ and exhibited no octahedral rotation and tilt. By contrast, Sr₃W₂O₉ and Sr₃Re₂O₉ were hettotype structures of Ba₃W₂O₉ at 298 K and demonstrated phase transitions related to octahedral rotation and distortion. The substitution of Sr for Ba at the A-site induced compressive chemical pressure and crystal structure changes. The crystallographic differences between Sr₃W₂O₉ and Sr₃Re₂O₉ were octahedral tilts related to the 5d electron configuration. In A₃B₂O₉ (A = Ba, Sr; B = W, Re), the substitution in the A- and B-site cations changed the octahedral rotation and distortion.

Na₂O–MgO–SiO₂ glasses were evaluated as a matrix of alkali waste solidification in the plutonium-uranium redox extraction (PUREX) process. Effects of ZnO, Al₂O₃, and B₂O₃ additions in small concentrations (≤4 mol %) on thermal stability against crystallization at high temperatures and water durability were studied. Infrared spectroscopy was used to evaluate the network structures of the Si–O and B–O bonds. Melt viscosity was measured by an inner rotation method in the temperature range between 1100 and 1300 °C. The results revealed that the addition of B₂O₃ and ZnO significantly contributed to respective enhancements of the thermal stability and water durability of silicate glasses with moderate melt viscosities at the operating temperatures of the glass solidification method for nuclear waste.

La₂O₃–TiO₂ (LT)-based glasses are promising materials for a wide range of optical applications because of their exceptionally high refractive indices and relatively low optical absorption in the visible wavelength range. In this study, LT-based multicomponent glasses were developed using the aerodynamic levitation technique, and their thermal stability, refractive index dispersion, and optical transmittance spectra were comprehensively analyzed. The addition of ZrO₂ and SiO₂ significantly improved the thermal stability of the glasses against crystallization. This enabled the fabrication of samples having diameters up to 25 mm, which is substantially larger than the typical glass size (approximately 2–3 mm) that is achievable through containerless processing. The LT-based glasses exhibited refractive indices at 2.161–2.315 at 587.562 nm, along with excellent transmittance characteristics relative to those of general optical glasses. An analysis of the refractive index dispersion based on the Lorentz model revealed that the densely packed structures and high electronic polarizabilities of oxygen atoms are critical factors in achieving ultra-high refractive indices and superior transmittance characteristics. Prototype lenses and wafer-shaped optical elements were fabricated using a glass molding press to demonstrate the potential of LT-based glasses for use in practical applications.

Tantalum borides have conventionally been produced via high-temperature solid-state reactions of the corresponding elemental raw materials. In this study, a unique chemical reaction design to add SiO₂ to the starting materials for an assist of TaB₂ formation is demonstrated. Powder mixtures of Ta₂O₅, B₂O₃, and SiO₂ were heated together with Na metal. TaB₂ was formed with concurrent generation of Na₂SiO₃ (otherwise known as water glass) in the reaction. Nearly single phase of TaB₂ powders with 50–200 nm particle sizes were obtained by by heating at a temperature range from 800 to 1000 °C followed by the successive removal of unreacted sodium and washing with ethanol and water. TaB₂ grains having a hexagonal prism morphology and sizes of several micrometers were grown in the sample heated at 1100 °C, possibly because molten Na₂SiO₃ with a melting point of 1088 °C acted as a flux.

We report a cross-linker-free 3D printing strategy for fabricating hierarchically porous nickel-cobalt oxide objects using highly concentrated dispersions of metal hydroxide acrylate nanoparticles. By employing an optimized photoinitiator, millimetre-scale nanoparticle-based structures were successfully printed without the need for cross-linking agents. Upon thermal treatment under inert atmosphere, the printed objects transformed into Co–Ni alloy/carbon nanocomposites via intermediate carbide phases. Subsequent oxidation removed carbon domains and produced porous metal oxide architectures with tuneable meso- to macroporosity, while preserving the original printed shapes. This solid–solid phase separation process enabled pore formation without sacrificial templates or collapse of structure. Our approach offers a streamlined route to functional ceramic frameworks, with potential applications in catalysis, energy storage, and separations.

Composite particles consisting of aragonite and hydroxy-carbonate apatite (HCA) were developed using strontium-containing aragonite [(Ca,Sr)CO₃] as the precursor via a phosphate-solution reaction under controlled conditions. An HCA layer with an approximate thickness of 1 µm was uniformly formed on the surfaces of the (Ca,Sr)CO₃ particles. The formation of this HCA layer was achieved using (Ca,Sr)CO₃; the introduction of Sr into aragonite, along with the adjustment of the phosphate solution’s pH and temperature, contributed to the moderate dissolution of aragonite. The gradual release of Ca²⁺ and Sr²⁺ ions from the particles, followed by their rapid reaction with phosphate ions in the solution, resulted in the formation of HCA on the particle surfaces.