High-Pressure and Temperature Syntheses and Structural Stability Studies of Some Rare-Earth Oxides

By using high pressure and temperature method for the first time and under the conditions of 3.2~4.0 GPa, 1 000~1 300 ℃, the synthetic experiments for the rare earth oxide systems of CeO2-R2O3 (R=Eu, Gd), CeO2-Tb4O11, Pr6O11-Tb4O7 were made, and the products of F-CeEuO3.5, -CeGdO3.5, -CeTbO3.5; B-CeEuO3, -CeGdO3, -CeTbO3 and B-PrTbO3, P-PrTbO3 were obtained. The PrTbO3 is a new material which has not been discovered in natural world up to date. The structural stability of the above products and NdYbO3, PrTmO3 has been measured by using high and low temperature X-ray powder diffraction method. The results indicated that some structural transformations from B-CeROx to F-CeROx (R=Eu, Gd, Tb) and from B-PrTbO3 to C-PrTbO3 occur at the temperature going from 300 ℃ to 1 000 ℃. The F-CeROx belongs to a fluorite-type structure with oxygen deficiency.