Chemical and Thermal Modification of PMN-Type Relaxor Ferroelectrics

PMN 型弛豫铁电体的化学和热改性

• 批准号: 9809035
• 负责人: Peter Davies
• 金额: $ 34.76万
• 依托单位: University of Pennsylvania
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1998
• 资助国家: 美国
• 起止时间: 1998-12-01 至 2002-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9809035&HistoricalAwards=false
• 关键词: Chemical; Thermal; Modification; PMN; Type

Davies9809035Following their discovery over thirty five years ago, relaxor ferroelectrics based on Pb(Mg1/3Nb2/3)03 (PMN) have attracted widespread interest for applications in multi-layer capacitors, transducers, electro-optic devices, and thin film memories. However, advances in the development of new PMN-type relaxors have been severely impeded by the apparent "frozen" nature of their chemical order, which has been assumed to be inert and unresponsive to thermal treatment. The inability to modify the nano-level cation order has also complicated attempts to characterize the local atomic structure or understand and model their relaxor response. Through experiments conducted on tantalate members of the PMN family of relaxors, Pb(Mg1/3Ta2/3)03 and its solid solutions with PbZrO3, Professor Davies has identified thermal conditions that can induce more than two orders of magnitude changes in the size of the chemically ordered domains. In contrast to other classes of perovskite relaxors, he has also found that the electronic properties of these large domain PMT systems retain a relaxor type response. These new observations cannot be reconciled in terms of the currently accepted "space charge" models for the structures of the PMN-type systems, and instead support a "random site" model for the cation order. Experiments using TEM and X-ray and neutron diffraction will be used to characterize the local chemistry and structure of the large domain systems. The dielectric response and ferroelectric properties will be measured. Several of the experiments will be carried out in collaboration with Professor Clive Randall of the Pennsylvania State University.%%%Professor Davies' discovery of methods to modify the cation order opens a new avenue of research for the PMN family of relaxor ferroelectrics. In this renewal project, the findings from the previous project will be utilized to develop a new class of large domain, chemically ordered niobate, tantalate, and tungstate relaxors that will have improved properties over those currently available. Collaboration with Professor Clive Randall of the Pennsylvania State University will enhance the experimental capability of the PI's group.***

35年前，基于Pb（Mg 1/3 Nb 2/3）O3（PMN）的弛豫铁电体被发现后，在多层电容器、换能器、电光器件和薄膜存储器中的应用引起了广泛的兴趣。 然而，在新的PMN型弛豫剂的发展的进展已严重阻碍了其化学顺序的明显的“冻结”的性质，这已被假定为是惰性的，对热处理无反应。 无法修改纳米级阳离子顺序也使表征局部原子结构或理解和模拟其弛豫响应的尝试变得复杂。 通过对弛豫体PMN家族的钽酸盐成员Pb（Mg 1/3 Ta 2/3）O3及其与PbZrO 3的固溶体进行的实验，Davies教授已经确定了可以引起化学有序结构域的尺寸发生两个以上数量级变化的热条件。 与其他类型的钙钛矿弛豫剂相比，他还发现这些大畴PMT系统的电子性质保持弛豫型响应。 这些新的观察结果不能调和的PMN型系统的结构，目前接受的“空间电荷”模型，而是支持一个“随机网站”的阳离子顺序模型。 使用TEM和X射线和中子衍射的实验将用于表征大畴系统的局部化学和结构。 将测量介电响应和铁电性能。 其中几项实验将与宾夕法尼亚州立大学的克莱夫兰德尔教授合作进行。Davies教授发现了改变阳离子顺序的方法，为弛豫铁电体PMN家族的研究开辟了新的途径。在这个更新项目中，以前项目的研究结果将用于开发一类新的大结构域，化学有序的钽酸盐，钽酸盐和钨酸盐弛豫剂，这些弛豫剂将具有比目前可用的更好的性能。 与宾夕法尼亚州立大学的克莱夫兰德尔教授合作将提高PI小组的实验能力。*