铁电-顺电扩散相转变的实验和统计模型

制备了扩散相转变铁电陶瓷系列(Ba_1-xLa_x)(Ti_1-yZr_y)O₃和扩散-非扩散相变铁电单晶系列K_0.2Na_0.2(Sr_pBa_1-p)_0.8Nb₂O₆。陶瓷采用一般铁电陶瓷制备工艺,单晶采用提拉法生长。测量了所有样品在-50—100℃范围内 关键词：

THE EXPERIMENT AND STATISTICAL MODEL OF FERRO-PARAELECTRIC DIFFUSE PHASE TRANSITION

A DPT ferroelectric ceramics system of (Ba_1-xLa_x)(Ti_1-yZr_y)O₃ and a DPT-SPT ferroelectric crystal serise of K_0.2Na_0.2(Sr_pBa_1-p)_0.8Nb₂O₆ have beenprepared by the ordinary ceramics manufacture technique and Czochralski technique respectively. The curves of dielectric constant vs. temperature of all samples have been measured. The semi-quantitive point-analyses of composition distribution have been obtained by the technique of SBM and EDAX. The inhomogeneity of composition distribution was discovered in both DPT ceramicses and DPT single crystal, but in SPT crystal no such fluctuation was found. It was shown that the diffuse curves of ε(T) is related to composition fluctuation directly. Therefore the Smolensky's composition fluctuation model for DPT was proved in experiment. According to this model, there is a statistical distribution of transition temperature, inside the DPT ferroelectrics. The theoretical calculation of dielectric constant with the change of temperature of all samples were done by using two different expressions of ε′(T, T_c). The theoretical results agree well with experimental curves.