Polarization Fluctuation Phenomena in Tungsten Bronze Ferroelectric Materials

9410141郭这项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起伏特性。在设计的极化条件下，在较宽的温度和频率范围内对Tb晶体的介电性能进行了测试，以揭示推测的极化起伏与晶体参数的关系。选定的铅-钡-铌氧化物固溶体单晶，包括近同型相界组成的单晶，将用于在不同极化条件下进行初步测试。预计计划活动的结果将在以下方面提供指导方针(但不是答案)：(1)特定的介电色散行为是否突出极化波动；(2)这种现象是结核家族特有的，即其晶体结构固有的？(Iii)极化涨落是热激活过程吗？%钨青铜结构的铁电材料包括一大类固溶体系统，在光学和电光应用方面具有巨大的潜力；然而，对其特性的了解是进一步探索新材料和对该家族中已知材料进行改性的关键。这项研究与铁电氧八面体材料(包括钙钛矿和钨青铜)的一般知识一起，将为研究选择、改性和设计具有理想和可控铁电性能的钨青铜铁电材料奠定基础。***

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. ***