Solid Phase Nucleation of Lead-Based Perovskites and their Properties

这是对α-Al_2O_3相变过程中控制形核原理和应用研究的更新。结果表明，通过添加外延引发反应的晶体结构相似的底物(即晶种)来控制反应的成核，几乎消除了反应的成核障碍，显著缩短了反应的潜伏期，缩短了反应时间和温度，减小了颗粒尺寸。目前的拨款包括对铅基钙钛矿、铅镁铌酸盐和铅锌铌酸盐的这些原理的研究。重点研究了晶种和混合金属氧化物前驱体之间的外延关系、成核钙钛矿的生长与输运路径的关系、微观结构的演变和电学性质。聚合物溶胶将被用来研究作为晶格失配和传输路径的函数的外延关系。种子溶胶将被用来确定相变动力学、微结构演变以及用于评估电学性能的样品的制备。正在研究的材料用于电子行业的电介质。它们很难合成出具有可重复性的特性。根据这项拨款进行的研究涉及降低加工温度的新加工技术，并有可能改善对结构的控制。对有经验的学生进行关于这些重要技术材料的研究的培训是补助金的一个重要组成部分。

This is the renewal of research on the principles and application of controlled nucleation during alpha aluminum oxide phase transformation. It was established that by controlling the nucleation of the reaction through the addition of crystallographically similar substrates (i.e., seeds) upon which the reaction is initiated epitaxially, the nucleation barrier to reaction is almost eliminated, the incubation period for reaction is significantly reduced, the reaction time and temperature are reduced, and the particle size is reduced. The current grant includes the study of these principles on lead-based perovskites, lead magnesium niobate and lead zinc niobate. The studies focus on the epitaxial relations between the seed crystal and mixed metal oxide precursor, growth of the nucleated perovskite as a function of transport path, microstructural evolution and electrical properties. Polymeric sols will be used to study epitaxial relations as a function of lattice mismatch and transport path. Seeded sols will be used to determine transformation kinetics, microstructural evolution and for preparation of specimens for evaluation of electrical properties. The materials being investigated are used in the electronic industry for dielectrics. They are difficult to synthesize with reproducible properties. The research under this grant is relevant to new processing techniques which lower the processing temperature, and potentially improve control of the structure. Training of students with experience to perform research on these technologically important materials is a significant component of the grant.