Pseudo-binary electrolytes of (100 − x)Li₄GeO₄·xLi₃VO₄ (x = 0, 10, 20, 30, 40, and 50 mol %) and pseudo-ternary electrolytes of 45Li₄GeO₄·45Li₃VO₄·10Li_aMO_b (M = B, Si, P, S, Mo, and W) with lithium superionic conductor (LISICON) type structures were prepared by mechanochemical treatment and subsequent heat treatment. For the (100 − x)Li₄GeO₄·xLi₃VO₄ heated samples with LISICON-type structure, the activation energy decreased with increasing Li₃VO₄ content, and the x = 50 sample showed a high conductivity of 1.1 × 10⁻⁴ S cm⁻¹ at 25 °C. The 45Li₄GeO₄·45Li₃VO₄·10Li_aMO_b heated samples with LISICON-type structure showed a conductivity of approximately 10⁻⁵ S cm⁻¹ at 25 °C, and the larger “a” as the Li content in Li_a(Ge_0.45M_0.1V_0.45)O_b contributed to improving the ionic conduction properties of this system.

A method of low-temperature liquid-phase sintering was used to prepare SrB₂Si₂O₈ glass-ceramics in order to simulate immobilization of ⁹⁰Sr, and the SrO–B₂O₃ system as a flux could avoid new impurities to be introduced into the solidified body. The sintering behaviors, mechanical properties and solidification behaviors of SrB₂Si₂O₈ were investigated. The crystalline phase of SrB₂Si₂O₈ was formed by liquid phase sintering at 1223 K. Additionally, adding Ca²⁺ improves the sintering behavior and mechanical properties of samples. The stable mineral phase of SrB₂Si₂O₈ is helpful to achieve a perfect effect on the immobilization of Sr. The Sr²⁺ leak mainly from the glass phase. Our results suggest that the key to resisting the leaking of Sr²⁺ is to form not only stable mineral phases but also stable glass phases.

The synthesis of porous titania microparticles with high specific surface area and sufficient photocatalytic activity is an important but challenging task. To this aim, micron-sized porous titania particles exhibiting photocatalytic activity comparable to that of titania nanoparticles were prepared in this study via hydrothermal treatment of porous hydrous titania particles. First, amorphous porous hydrous titania particles were prepared via hydrolysis of titanium alkoxide followed by partial dissolution of the particle surface by soaking in ethanol. Then, porous hydrous titania particles dried at 75 °C (Dry particles) and without drying (Wet particles) were respectively crystallized using hot water (<100 °C) or via hydrothermal treatment. Both types of particles were crystallized to anatase having a mesoporous structure and a preserved spherical outer shape under hydrothermal treatment. The mesoporous structure was controllable by tuning the treatment temperature, especially in the case of Wet particles. The porous titania particles prepared from Wet particles showed better photodegradation activity toward Evans blue under UV irradiation than those prepared from Dry particles, which is attributable to the distortion of titania crystallites prepared from Wet particles. In fact, despite their micron-order size, the photodegradation ability of Wet particles hydrothermally treated at 160 °C for 24 h was comparable to that of AEROXIDE^® TiO₂ P25.

The effects of mixing and grinding on solid-state reactions were separately investigated using a wet-type super atomizer for dispersing particles without breaking them. The solid-state reaction of kaolinite [Al₂Si₂O₅(OH)₄] with calcium carbonate (CaCO₃) to form metastable CaAl₂Si₂O₈ was carried out, with the raw materials being ground prior to the reaction. Notably, rough mixing of the raw materials before the reaction resulted in gehlenite (Ca₂Al₂SiO₇). After grinding methoxy-modified kaolinite, an expanded kaolinite (Ex-Kaol) swollen in methanol, and calcite particles, the resultant mixed-methanol dispersion was vigorously agitated for one pass using a wet-type super atomizer with a discharge pressure of 200 MPa. No detectable change in the X-ray diffraction (XRD) patterns was observed between the pristine and treated raw materials, indicating that the stacking order of the kaolinite, which dominates the reaction rate of metastable CaAl₂Si₂O₈, was not changed by the treatment at 200 MPa. The treated raw materials gave metastable CaAl₂Si₂O₈ after calcination at 900 °C for 4 h, although the calcined product prepared from unground raw materials treated at 200 MPa contained gehlenite. The results indicated that both grinding and mixing procedures dominated the formation of CaAl₂Si₂O₈ by the solid-state reaction of kaolinite with CaCO₃.

Sulfide electrolytes are among the most notable materials because of their high ionic conductivity and ductility. Their primary drawback is that they are sensitive to humidity and must be handled in an inert atmosphere to prevent degradation. Understanding the degradation mechanism is necessary to establish methods for overcoming it; however, whether or not it depends on the composition of the electrolytes is not yet clear. In this study, we systematically investigated the crystal structure changes in a humid atmosphere for crystalline sulfide electrolytes (thio-LISICONs). Eight thio-LISICONs, Li_xMS₄ (x = 3–5; M = Al, Ga, Si, Ge, Sn, P, As, and Sb), were prepared using a mechanochemical process and subsequent heat treatment. The exposure behavior was observed using in situ humidity exposure X-ray diffraction (XRD). In a humid atmosphere with a dew point of −8 °C, the electrolytes, transformed into new hydrates, all except for Li₅AlS₄ and Li₅GaS₄, which did not change. Hydrated Li₄MS₄ (M = Si and Ge) has the same crystal structure as that of the known hydrate Li₄SnS₄·13H₂O. The crystal structures of hydrated Li₃MS₄ (M = P, As, and Sb) were identical to each other but different from those of Li₃AsS₄·8H₂O. This study revealed that the hydration behavior of the sulfide electrolytes depends on their central element groups.

The electronic structure of V-doped ZrSiO₄ is estimated by using the generalized gradient approximation. When a V atom replaces a Zr or Si atom, localized V 3d states appear in the bandgap of ZrSiO₄. Four different supercells with V doped in the interstitial site of ZrSiO₄ are constructed by vacating one Si atom to satisfy the electroneutrality. When the Si near the doped V is vacant, the energy positions and splitting states of the V 3d states in the bandgap are almost identical to those when a V atom is substituted for a Si atom. By contrast, when the Si site away from the V is deficient, the characteristics of V 3d states in the bandgap are significantly different from those where V and Si are substituted. A comparison of the total energies of four supercells with interstitially doped V indicates that the total energy of the vacant Si site near the doped V is lower than that of the vacant Si site distant from V. Further, the total energy when interstitial V and Si vacancies are close to each other in the supercell is almost equal to that when Si and V are directly substituted. Therefore, the possibility that V substitutes not only the interstitial sites of ZrSiO₄ but also Si cannot be ruled out.

Tantalum nitride (Ta₂N) nanocrystals have been successfully synthesized at 650 °C through a chemical reaction in an autoclave. The X-ray powder diffraction pattern indicates that the product is hexagonal phase Ta₂N. Transmission electron microscopy image shows that the obtained Ta₂N product is consist of nanoparticles with an average size of about 50 nm. Furthermore, the thermal gravimetric analyzer (TGA) result indicates that the product has good thermal stability and oxidation resistance below 300 °C in air.

In this study, V-doped, Al-doped, (Al,V)-doped, and pure ZrO₂ powders were prepared using a complex polymerization method, and the thermally decomposed products were characterized using powder X-ray diffraction (XRD) and scanning electron microscopy (SEM). After calcination at 500 °C in air, several small broad peaks were observed in the XRD patterns of all samples. As the heating temperature increased, the phase-transition behavior of ZrO₂ varied among the four samples. The phase transition from tetragonal to monoclinic ZrO₂ was enhanced in ZrO₂ doped with V, but suppressed in ZrO₂ doped with Al. The tetragonal phase (t-ZrO₂) was dominant in the sample co-doped with Al and V and in Al-doped ZrO₂ samples calcined at 700 °C and below, and no diffraction peaks associated with the monoclinic phase (m-ZrO₂) were observed. However, after calcination at 800 °C, the diffraction peaks of t-ZrO₂ disappeared, and a single phase of m-ZrO₂ was observed. SEM observations revealed that the V-doped ZrO₂ particles were composed of fine particles in the range of 20–30 nm. In contrast, the SEM images of the (Al,V)-doped ZrO₂ powder indicated an increase in agglomerate size compared with that without Al doping. However, elemental analysis using energy-dispersive X-ray spectroscopy (EDX) showed no agglomeration or segregation of Al or V.