UO2-ZrO2固溶体的形成机理和微观结构演变分析

摘要

The mechanism of diffusion of ion and chemical transformation rule on the formation of solid solution for UO2-ZrO2 were investigated by XRD patterns and SEM micrographs.The results show that ZrO2 with UO2 diffuses and reacts more easily than UO2 with ZrO2.The phase transformation of ZrO2 from monoclinic to tetragonal enhances the formation of UO2 solid solution.The structural evolution of pellet depends on the process of the atoms diffusing across the (UxZr1-x)O2 and (ZryU1-y)O2 layers and the reaction at the interface.The differences of cation radii and crystal structure result in that ZrO2 can dissolve into UO2 more than UO2 into ZrO2,which leads the formation of solid solution mainly depends on the growth of UO2 solid solution,and the ZrO2 solid solution decreases gradually during the sintering process.The formation of solid solution is mainly the substitution of Zr4+ for U4+ via the schottky defect.%采用XRD谱和SEM图像研究了UO2-ZrO2芯块固溶体形成过程的离子扩散和化学转变规律.结果表明,ZrO2扩散至UO2界面与之发生反应较UO2扩散至ZrO2界面与之发生反应更容易.ZrO2斜方向四方的同素异构转变有利于UO2固溶体的形成.芯块的结构演变依赖于离子在UO2与ZrO2界面(UxZr1-x)O2和(ZryU1-y)O2层的扩散和反应.离子半径和晶体结构的差异使得ZrO2固溶于UO2优于UO2固溶于ZrO2,导致芯块中的UO2固溶体长大和ZrO2固溶体逐渐减小.UO2固溶体的形成主要是通过schottky缺陷,使Zr4+离子置换U4+离子.