Polarization Fluctuation Phenomena in Tungsten Bronze Ferroelectric Materials

本研究计划活动的主要目标是确定钨青铜（TB）结构铁电材料的极化波动特性。在较宽的温度和频率范围内测试TB晶体在设计极化条件下的介电性能，以揭示推测的极化波动与晶体学参数的依赖关系。选定的铅钡铌氧化物固溶体单晶，包括近形态取向相边界组成的晶体，将用于在各种极化条件下进行初步测试。预计计划活动的结果将提供以下方面的指导（但不是答案）：(i)具体的介电色散行为是否强调极化波动；（ii）这种现象是否为结核科所特有，即其晶体结构所固有？（三）极化波动是一个热激活过程吗？（四）化学成分波动对推测的极化波动有何影响？钨青铜结构铁电材料涵盖了一大类在光学和电光应用方面具有巨大潜力的固溶体体系；然而，了解它们的特征极化特性是进一步探索新材料和对已知材料进行改性的关键。本研究结合对铁电氧八面体材料（包括钙钛矿和钨青铜）的总体认识，将为选择、修饰和设计具有理想和可控铁电性能的钨青铜铁电材料的研究奠定基础。＊＊＊

9410141 Guo The primary goal of this research planning activity is to identify polarization fluctuation characteristics in ferroelectric materials of the tungsten bronze (TB) structure. Dielectric properties of TB crystals under designed poling conditions in a broad temperature and frequency range are to be tested to reveal the dependence of the speculated polarization fluctuation on the crystallographic parameters. Selected single crystals of lead barium niobium oxide solid solutions, including crystals of near morphotropic phase boundary compositions, will be used to perform preliminary tests under various poling conditions. The outcome of the planned activities is expected to offer guidelines (but not the answers) on (i) whether the specific dielectric dispersive behavior underlines polarization fluctuation; (ii) is this phenomenon characteristic to the TB family, i.e., inherent to its crystallographic structure? (iii) is the polarization fluctuation a thermally activated process? and (iv) what is the role of chemical composition fluctuation on the speculated polarization fluctuation? %%% Ferroelectric materials of tungsten bronze structure encompass a large family of solid solution systems with great potential in optical and electrooptic applications; however, an understanding of their characteristic polarization properties is a key still lacking for further exploration of new materials and modification of known materials in this family. This research, along with knowledge on ferroelectric oxygen octahedral materials (including the perovskites and the tungsten bronzes) in general, will give the foundation for researchto select, modify and design tungsten bronze ferroelectric materials with desired and controllable ferroelectric properties. ***