铌镁酸铅类钙钛矿结构铁电多晶体的制备技术

铌镁酸铅(PMN)类化合物是一类弱铁电特性的ABO_3型复合钙钛矿结构铁电弛豫体。利用在A/B位固溶外来离子(例如,Sr、Ba和Ti等)的原理,改变该类化合物基固溶体的电负性差值φ和加权结构容差因子t值,达到合成全钙钛矿结构相的目的。根据电负性差值理论和钙钛矿结构容差因子理论,本文提出了铌镁酸铅类化合物钙钛矿结构相稳定性优值参数M的新概念。基于M值定义和PZN基固熔体的实验数据,推算出钙钛矿结构相稳定性临介优值Mc=1.67,并用以设计和优选PMN和PZN基多晶体最佳配方,优化材料性能。同时研究了钙钛矿结构相合成程度与MnO_2添加量和Mg偏离化学计量比程度的关系。研制出性能稳定、特性优良的新材料。

FABRICATION OF PMN TYPE FERROELECTRIC RELAXORS WITH PEROVSKITE STRUCTURE

Lead Magnesium Niobate is a kind of perovkite type ferroelectric relaxors with DPT charateristic. Based on the fact that some cations, e.g., Sr, Ba and Ti el at, A/B-side-coordination changes the electronegative difference and tolerance factor of this kind of relaxor type ferroelectrics and enhances the formation of perovskite structure, a concept of Figure of Merit of the stability of perovskite structure for the ferroelectric relaxors studied is proposed. A precalcining technique is employed to fabricate polycrystalline samples of the ferroelectric relaxors. The relationships between the percentage of the provskite phase and the Mn composition, the Mg composition deviation from stoichiometry and the second ferroelectric compound soluted are discussed. The dielectric properties of these solid solutions are also presented. A composition with high dielectric performance is discovered.