溶胶-凝胶法制备的纳米PrO_y-ZrO_2固溶体的表层和体相结构

Structure on Surface and the Bulk Shell of Nanosized PrO_y-ZrO_2 Solid Solution Prepared by Sol-gel Method

用改进的柠檬酸溶胶-凝胶法制备了纳米PrOr-ZrO2固溶体．采用XRD，Raman和TEM等技术对纳米PrOy-ZrO2进行了表征．结果表明，改进的柠檬酸溶胶-凝胶法制备的PrOy-ZrO2固溶体于650℃焙烧后晶粒大小在5—10nm之间；于950℃焙烧（Pr〉16％）后晶粒大小在20nm左右．Pr能有效地使ZrO2稳定在四方或立方晶相．随Pr含量的增加，PrOr-ZrO2固溶体的物相结构从单斜相逐步向四方和立方相转变．XRD和Raman得到的物相结构的差别表明，PrOy-ZrO2固溶体表层和体相结构存在不一致性，随Pr含量增加，体相逐步按照m→t→c的物相转变，表层按照m→t→t^n的物相转变．表层更易生成低对称性和无序结构．

The characterization for PrOy-ZrO2 solid solutions prepared by improved sol-gel method was performed by means of Raman, XRD, TEM and so on. It is found that the grain size of PrOy-ZrO2 solid solution calcined at 650 ℃ is 5-10 nm, and that of PrOy-ZrO2 solid solution calcined at 950 ℃ [x（Pr） 〉 16% ] is about 20 nm. At a higher Pr content, phase transformation towords a higher-symmetrical phase （ tetragonal or cubic） was observed. The results of phase analysis obtained by Raman spectroscopy were different from the corresponding results of XRD, which implies a structure difference between the surface and the bulk shell of the samples. With the increase of the Pr content, the m→t→w phase tramsformation occurred in the bulk area and the m→t→t＇＇ phase tramsformation occurred in the surface area. The surface region is more easily to form a low symmetry and disorder structure.