イットリウムを含有する水和ジルコニア微粒子の相変化

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Yttrium-containing monoclinic hydrous-zirconia fine particles were heated from 300 to 700℃ to investigate the phase change to 2.8 mol% Y_2O_3-doped tetragonal ZrO_2. Both ZrOCl_2・8H_2O and YCl_3・6H_2O were dissolved into aqueous solutions and then boiled to make the hydrous-zirconia particles. The hydrous-zirconia particles containing Y(OH)_3 were prepared by dropping aqueous ammonia into the boiled solutions, while hydrous-zirconia particles containing YCl_x(OH)_y・nH_2O were obtained by spray-frying of the boiled solutions. The monoclinic-to-tetragonal phase change of hydrous-zirconias containing Y(OH)_3 was observed at 400℃ by X-ray diffraction. The hydrous-zirconias containing YCl_x(OH)_y・nH_2O transformed to tetragonal phase at 500℃. The results of chemical analysis indicated that the atomic ratio of Cl/Y decreased with increasing heat-treatment temperature. At 500℃, this atomic ratio became less than 1. These experimental results suggested that the hydrous-zirconias containing YCl_x(OH)_y・nH_2O transformed to tetragonal phase through the decomposition reaction of YCl_x(OH)_y・nH_2O. Therefore, it is concluded that as the decomposition of YCl_x(OH)_y・nH_2O affects phase change, the temperature of phase change of hydrous-zirconias containing YCl_x(OH)_y・nH_2O becomes higher than those containing Y(OH)_3. X-ray diffraction and BET specific surface area measurements revealed that for hydrous-zirconia containing Y(OH)_3, the primary particle of small size with monoclinic phase was transformable to tetragonal phase at lower temperature comparing with that of large size. The hydrous-zirconias containing YCl_x(OH)_y・nH_2O with smaller particle size also showed the similar tendency. This tendency can be explained by the increase of the points contacted with yttrium and the shortening of diffusion length in the hydrous-zirconia particle with small size.
社団法人日本セラミックス協会の論文
1995-06-01

イットリウムを含有する水和ジルコニア微粒子の相変化

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