ゾル-ゲル法によって合成したZrO_2-YO_<1.5>-TiO_2系酸化物の相関係 : 蛍石構造相へのTiO_2固溶限

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Phase relationship in ZrO_2-YO_<1.5>-TiO_2 system, solid solubility of TiO_2 in yttria stabilized zirconia (YSZ) and phase stability have been investigated for the samples prepared by sol-gel mehtod after the heat treatment between 1073 and 1923 K for 10 to 100h using a powder X-ray diffraction analysis.The lattice parameter of the fluorite (FC) phase at fixed concentration of yttria was found to decrease linearly with increasing TiO_2 concentration by the substitution of Ti^<4+> for Zr^<4+> ions.Although decrease in solid-solubility limit of TiO_2 in (YO_<1.5>)_<0.250>-(Zr_<0.750_-x>Ti_x)O_2 with increasing annealing period suggests that the phase relationship obtained in this experiment includes metastability of the solid solution, the phase relationship satisfies the phase rule, except for the composition regime relating the formation of Zr_3Y_4O_<12>, YO_<1.5> and Y_2Ti_2O_7.The ternary phase relationships have been given for the annealing conditions of 1923 K for 6h, 1773 K for 10h, 1473 K for 60h, 1273 K for 10h and 100h and 1073 K for 10h in air.The ternary eutectic temperature was estimated to be about 1823 K from the phase relationship and the solid solubility of TiO_2 in (YO_<1.5>)_<0.250>-(Zr_<0.750_-x>Ti_x)O_2 between 1273 and 1773 K.The present results suggest that the solid solubility of TiO_2 in YSZ is much smaller than the reported value.
1998-09-01