Polarization Fluctuation Phenomena in Tungsten Bronze Ferroelectric Materials

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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. ***