| Homogenous coprecipitation of Ce3+,Y3+ was performed to prepare (Ce0.8Y0.2)2(C2O4)3 solid solution, by using diethyl oxalate, cerium nitrate and yttrium nitrate as starting material, and urea as pH adjuster. The co-precipitates produced under different conditions were analyzed by TG-DTA and the result indicated that the co-precipitates (n=0～35.5, n: mole ratio of urea to diethy oxalate) produced were oxalate solid solution. From SEM observation its particle average size decreased from 10μm to 0.5μm with increasing n from 0 to 35.5. The oxides derived from the oxalate solid solutions were comfirmed to be Y-doped CeO2 by XRD analysis and lattice constant calculation. Its crystallite size is about 10nm. Nanocrystalline Ce0.8Y0.2O1.9 was heat treated at 500900℃in air. Grain growth was investigated with x-ray diffraction (XRD) by means of scherrer formula. The results of the experiment suggested that the grain growth of the nanocrystalline Ce0.8Y0.2O1.9 followed the kinetic equation d-d0=Aexp[-Ea/(RT)](t-t0). The active energy of the grain growth was estimated to be 73.1 kJ/mol.Dependence of the Ce0.8Y0.2O1.9 density and grain size on the sintering temperature (10001500℃) was achieve by investigating the sintering behavior of the samples. Statistical analysis of grain size by SEM observation suggested that grain growth of Ce0.8Y0.2O1.9 followed different kinetic equations when sintered at two different temperature ranges. At low temperature range of (1000～1300℃), the active energy of grain growth was relative small (171.1kJ/mol), indicating a weak effect of temperature on the grain size. However, at high temperature range of (1300～1500℃), the active energy became great (479.8 kJ/mol), indicating the grain growth was sensitive to the sintering temperature. Dispersion of distribution of grain size also became large. The relative density of the sintered body increased fast with increasing temperature and reached 98.4% at 1400℃. Then it increased gradually at temperature above 1400℃. |
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