Enhancement of the thermal stability of a catalyst is an efficient way to improve the catalytic activity of a catalytic reaction performed at high temperature. In this study, cerium oxide (ceria, CeO₂) with a high thermal stability was synthesized by controlling the agglomeration of the primary particles via the thermal hydrolysis of ceric nitrate, accompanied by testing for the catalytic combustion of methane (CH₄). The specific surface area of this material after calcination at 1,173 K for 5 h was 50 m²/g, which was much higher than that of the two reference materials (ceria made via precipitation of cerous nitrate using aqueous ammonia at 4.1 m²/g, and the Japan reference catalyst JRC-CEO-1 at 1.4 m²/g). The ceria made via thermal hydrolysis showed high crystallinity and a much higher pore volume, which resulted in excellent thermal resistance. For O₂ conversion in ceria, catalyzed CH₄ combustion at 923 K, the ceria created in this study demonstrated higher activity than that for either reference. The high CH₄ combustion performance was due to the high specific surface area and to a superior oxygen storage capacity (OSC) even after a combustion test.

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The effect of Ce dopant on phase, morphology, optical property and photocatalytic activity of ZnWO₄ was investigated in this research. The products were characterized by X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy and UV–visible spectroscopy. The results showed that the pure product was monoclinic ZnWO₄ nanorods with the growth direction of [021] and that Ce³⁺ and W⁶⁺ ions contained in the Ce-doped products. The photocatalytic activities of the photocatalysts were evaluated through the degradation of methylene blue (MB) solutions under UV-light illumination. The results showed that the efficiencies for MB photocatalytic degradation were influenced by Ce dopant. The photocatalytic activities of the Ce-doped ZnWO₄ samples were higher than that of the pure ZnWO₄.

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We synthesized Eu₂Zr₂O₇ and La₂Zr₂O₇ using high purity ZrO₂ of extremely low Hf content. The crystal structures of Eu₂Zr₂O₇ and La₂Zr₂O₇ were refined by the Rietveld analysis of the powder X-ray diffraction data (indexed as a cubic pyrochlore-type structure, space group: No.227, Fd3m) measured from 1173 to 298 K in a dry condition and from 1173 to 323 K in a wet condition. The crystal structure of La₂Zr₂O₇ is near to an ideal pyrochlore-type structure, whereas that of Eu₂Zr₂O₇ is a distorted pyrochlore-type structure. The thermal expansion coefficients of Eu₂Zr₂O₇ were larger than those of La₂Zr₂O₇. The value of the equivalent isotropic atomic displacement parameters (B_eq) calculated from the anisotropic atomic displacement parameter for the Zr in Eu₂Zr₂O₇ at 298 K was around 1.4 Ų, and the increase of this value in Eu₂Zr₂O₇ with increasing temperature was smaller than that in La₂Zr₂O₇.

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Cr-doped calcium titanate (CaTiO₃) pigments with prism-like shape were synthesized by a simple solvothermal process without any surfactants. The colouring mechanism and performance of Cr-doped CaTiO₃ yellow pigment samples were investigated by X-ray diffraction, diffuse reflection spectroscopy, field scanning electron microscopy and colorimeter. When Cr-doping concentrations were 0.01–0.05% (mole fraction, the same below), solid solution formed so that the yellow pigments would have a CaTiO₃ phase composition. The intensity of the yellow colour in the pigment samples was related to the presence of Cr ions. The optimum yellow pigment was achieved when the Cr-doping concentration was 0.03% mol. At a high temperature of 1280°C, Cr-doped CaTiO₃ yellow sample provided a stronger and more intense colour as Cr ions dissolved into the stable CaTiO₃ structure. This solvothermal preparation method provides a simpler way to synthesize a more colourful ceramic pigment that can be applied in ceramic decoration or inkjet printers.

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The mullite columnar structure are prepared by a dry-press method using waste gangue substituted for kaolin clay. The properties e.g., water absorption, bulk density and bending strength of the samples fired at the temperature range of 1300–1550°C are studied. The microstructure of mullite columnar structures are characterized by X-ray diffraction and field emission scanning electron microscopy with an energy dispersive X-ray spectroscopy. The results reveal that waste gangue substituted for the kaolin is available for mullite columnar structure. Impurities in waste gangue e.g., TiO₂ and Fe₂O₃ lower the formation temperature of mullite columnar structure, which endow the samples with high refractoriness. Due to the presence of interlocking structure constructed by mullite crystals, the sample achieves the optimum bending strength of 97.6 MPa at the temperature of 1400°C, which is future application in refractory materials. The dry-pressed preparation method provides a simple way to synthesize mullite columnar structure using waste gangue substituted for kaolin clay that can be future applied in lightweight refractory industry.

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