刚玉结构铌、钽酸盐晶体生长及高压物性研究

Binary niobate and tantalate materials possess excellent optical, magnetics and microwave dielectric properties. In this project, corundum-type tantalate and niobate crystals will be grown by optical floating zone method for the first time, while the key problems, such as the growth conditions and mechanism, will be also studied for these systems. At ambient conditions, physics properties of as-grown crystals will also be investigated systematically. Polarized Raman and infrared spectroscopies on oriented samples will allow us to assign Raman and infrared vibration modes for the corundum- type tantalate and niobate crystals. While the dielectric response of a sample in the microwave region is dominated by the contribution of their optical polar phonon modes; moreover, intrinsic dielectric merit factors of the as-grown crystals can also be determined from the polarized infrared spectra together with the Raman. By using conventional diamond anvil cell (DAC), variation of structure, optical and microwave dielectrics properties for tantalate and niobate under high-pressure or some other extreme conditions will be studied. The possibility for regulate the physics properties of materials by high-pressure will also be investigated. The Nb2O9 and Ta2O9 in the corundum-type niobium and tantalate should play a dominate role in the determination of their physics properties, therefore, detailed and systematic investigations on the variation law of the Nb2O9 and Ta2O9 units under high- pressure will give a universal law of corundum-type niobium and tantalate. They will provide the experimental evidence and technology support for the improvement of the microwave dielectric and luminescence properties of corundum-type niobium and tantalate.

二元铌、钽酸盐材料具有优异的光学、磁学和微波节电介电性能。本项目拟采用光学浮区法进行刚玉结构的铌、钽酸盐单晶体生长,并对生长单晶体的结构和物性进行研究；采用原位金刚石压砧高压实验技术（DAC），研究该材料在高压等极端条件下的结构、电学、光学、磁学性能变化规律。样品在微波段的介电响应，取决于分子内部离子位移极化，与光学极化声子模联系密切，可以通过测量样品的红外光谱和拉曼光谱获得样品的本征微波介电性能，在常压条件已完美应用，本项目将首次通过红外与DAC结合，研究高压下样品微波介电性能变化规律，有希望为高压原位测量材料的微波介电性能提供一种新方法。探索利用压力对其基本物理性质进行调控的可能性，尤其刚玉结构的铌、钽酸盐中，Nb2O9、Ta2O9原子集团为普遍存在的基本结构单元，且物质的基本性质由它们决定，对它们研究有望获得普适规律。为制备具有高荧光和微波介电性能的铌、钽酸盐材料提供重要实验依据。

二元铌、钽酸盐材料具有优异的光学、磁学和微波节电介电性能。运用光学浮区法进行刚玉结构的铌、钽酸盐单晶体生长,并对生长单晶体的结构和物性进行研究；通过同步辐射技术和拉曼光谱技术原位测量温度和压力对所生长晶体样品结构及光电性能的影响。我们首先进行了Mg4Nb2O9和Mg4Ta2O9的晶体生长，通过优化生长参数，成果获得刚玉结构Mg4Nb2O9和Mg4Ta2O9晶体，并获得了其常规条件下的性能。再运用变温平台探索了其温度作用下的结构变化规律，又运用原位金刚石压砧高压实验技术（DAC）对样品进行测量，掌握了其压力作用下晶体结构及光电性能变化规律。探索利用压力和温度对其基本物理性质进行调控的可能性，为制备具有高荧光和微波介电性能的铌、钽酸盐材料提供重要实验依据。