某些稀土氧化物的高温高压合成及其结构稳定性研究

 首次用高压高温方法，在3.2~4.0 GPa，1 000~1 300 ℃下，对CeO₂-R₂O₃（R=Eu，Gd），CeO₂-Tb₄O₁₁，Pr₆O₁₁-Tb₄O₇稀土氧化物进行合成实验，得到具有F型结构的CeEuO_3.5，CeGdO_3.5，CeTbO_3.5；B型结构的CeEuO₃，CeGdO₃，CeTbO₃，PrTbO₃和P型结构的PrTbO₃。PrTbO₃是迄今自然界尚未发现，文献未见报导过的新物质。对上面的产物和NdYbO₃、PrTmO₃，利用高、低温X射线衍射实验，检测了其结构的稳定性，结果指出：从300 ℃直到1 000 ℃，发生由B型CeRO_x向F型CeRO_x（R=Eu，Gd，Tb）、B型PrTbO₃向C型PrTbO₃的结构转变。F型CeRO_x属于氧缺位萤石型结构。

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-CeEuO_3.5, -CeGdO_3.5, -CeTbO_3.5; 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-CeRO_x to F-CeRO_x (R=Eu, Gd, Tb) and from B-PrTbO₃ to C-PrTbO₃ occur at the temperature going from 300 ℃ to 1 000 ℃. The F-CeRO_x belongs to a fluorite-type structure with oxygen deficiency.