Li₁₀GeP₂S₁₂ solid electrolytes, which exhibit ionic conductivity comparable to that of organic electrolytes, have attracted attention. An excess sulfur solution method for short-time synthesis of Li₁₀GeP₂S₁₂ has been proposed, and it has been revealed that the heat treatment process using a titanium boat improves ionic conductivity compared to other combustion boats, such as quartz boats. To elucidate the mechanism, analysis including X-ray diffraction and Raman spectroscopy were conducted, and they revealed the formation of lattice distortion related to the enhanced ionic conductivity. Furthermore, applying a Ge-rich composition precursor successfully achieved the liquid-phase synthesis of Li₁₀GeP₂S₁₂ solid electrolyte with high ionic conductivity.

Pure magnesium powders added 0.50 g of stearic acid as process control agent (PCA) were mechanically milled (MMed) 24 hours using a vibration ball mill. MMed powders were consolidated into bulk materials by spark plasma sintering (SPS). Changes in hardness, solid-state reactions, bulk density and thickness of the SPS materials have been examined by hardness measurements, an X-ray diffraction, measurements of weight, diameter, height and vernier caliper, respectively. The Vickers hardness of the SPS material decreased with increasing sintering temperature. A minimum hardness value of the SPS material was 19 HV. No effect of sintering pressure on thickness of the SPS materials was observed. Formation of MgH₂ by solid-state reaction during the SPS process was observed for the SPS materials. The sintering temperature contributed to the expansion of the SPS materials than the sintering pressure.

Calculated phase diagram of C-Co-V-W quaternary system was attempted to investigate constitution phases of WC-VC-Co cemented carbide during liquid phase sintering. It was found that VC phase could not exist stably for low addition region of VC over liquidus temperature of Co phase in (VC-20Co)-(WC-20Co) pseudo-binary system. It was considered that the formation of (V,W)C phases was classified into three types depending on the additive amount of VC. For the additive amount of less than solubility limit of VC in solid Co at solidus temperature, (V,W)C phase precipitates on WC/Co interfaces from solid Co on low temperature side during cooling. In the range of additive amount between solubility limit in solid Co at solidus temperature and solubility limit in liquid Co at liquidus temperature, (V,W)C phase crystallizes out of liquid phase in temperature during solidification of Co due to the difference between solubility limit in liquid Co and that in solid Co. Above additive amount of solubility limit in liquid Co at liquidus temperature, (V,W)C phase exists in equilibrium with liquid Co above liquidus temperature. It was concluded that inhibition mechanism of grain growth was to differ at solubility limit of VC in Co liquid phase.

Since the invention of cemented carbide about 100 years ago, it has developed through extensive research in both its fundamental and applied fields. In recent years, the manufacturing industry has demanded higher productivity and efficiency, which requires further improvements in cemented carbides. This study began with the steel cord wire drawing dies, which are categorized as wear-resistant tools. It was found that the interface properties of WC significantly impact on the lifetime of steel cord wire drawing. In the wear of cemented carbide dies for steel cord wire drawing, HIP-processed alloys with TaNbC addition showed excellent performance, and further annealing treatment dramatically improved lifetime by a factor of about five. Moreover, ultrafine cemented carbide with fine particle Ti(C,N) additives, which improved interface properties, was found to have a significant effect on inhibiting the growth of WC grains by pinning WC particle surfaces with fine Ti(C,N) particles. Furthermore, ultrafine cemented carbide with a composite addition of fine Ti(C,N) and Cr₃C₂ achieved world-leading strength, recording an average transverse rupture strength of 4.6 GPa and a maximum strength of 5.0 GPa. Tests with this Ti(C,N)-Cr₃C₂ composite-added ultrafine cemented carbide on actual equipment showed results that outperformed conventional products in all cases.

A Li₁₀GeP₂S₁₂-type lithium-ion conductor Li₁₀P₃S₁₂Br was investigated as a potential solid electrolyte for composite anodes in all-solid-state lithium-ion batteries. Cyclic voltammetry measurements using an Au/Li₁₀P₃S₁₂Br/Li cell revealed that Li₁₀P₃S₁₂Br possesses a sufficiently wide electrochemical window, making it suitable for anode reactions at low potentials. Spherical graphite-Li₁₀P₃S₁₂Br composite anodes, fabricated via rotary mixing, exhibited lithium (de)intercalation activity, demonstrating the feasibility of Li₁₀P₃S₁₂Br as an electrolyte for all-solid-state battery anodes. Composite anodes with a higher proportion of Li₁₀P₃S₁₂Br relative to graphite exhibited improved cycle retention of charge-discharge capacities. A composite comprising graphite (d₅₀: 8 µm) and Li₁₀P₃S₁₂Br (d₅₀: 0.3 µm) in a 20:80 wt.% ratio achieved a discharge capacity of 365 mAh g⁻¹ at the 30th cycle. In contrast, the 50:50 wt.% composite exhibited a notable decrease in lithium intercalation capacity in the stage 2 (LiC₁₂) and stage 1 (LiC₆) regions. These results suggest that reducing the lithium diffusion distance within graphite particles is crucial for enhancing the intercalation properties of graphite/Li₁₀P₃S₁₂Br composite anodes.

Metal oxides have been prepared with high temperature annealing for a long time. However, metal oxides are synthesized in nature at ordinary temperature and atmospheric pressure. In this study, learning from nature, metal oxides were synthesized at room temperature. This study focuses on “Formation and two-dimensional patterning of particle self-assembled structure”, “Synthesis of ceramics in aqueous solution and their two-dimensional patterning”, “Microstructure control and crystal face control of ceramics”, “Gas and odor sensors with highly active crystal faces”, and “Molecular sensors for detection of environmental toxin or cancer marker”. In particular, concept of crystal growth control and nanostructure control of metal oxides was proposed. The two-dimensional patterning of ceramic nanostructured films and particle self-assembled structure was achieved. In addition, a dendritic structure of tin oxide with metastable {101} crystal facets was developed in aqueous solution. They were applied to chemical sensors and gas sensors.