稀土掺杂Bi4Ti3O12基铋层状高温压电单晶的荧光温度特性及其光—电耦合机理研究

It is of great importance for novel high-temperature piezoelectric sensor to develop multifunctional materials with high Curie temperature, good piezoelectric properties as well as better photoluminescence performances. Bi4Ti3O12 solid solution has attracted great attentions due to its high Curie temperature, excellent thermal stability, and good fluorescence performances after rear earth doping. In this project, Bi4Ti3O12 single crystals doped with rare earths are grown by top seed solution growth method. The quality and property of single crystal can be improved through the optimization of growth parameters, formula composition and after-treatment. The temperature dependence of piezoelectric and fluorescence properties is investigated. The characteristic and dynamic evolution of microstructure, including the morphology of ferroelectric domains and the phase structure, as function of temperature are investigated by the in-situ fluorescence spectra combined with the in-situ Raman and XRD, which reveals the microscopic mechanism of the piezoelectric and fluorescence properties. Finally, to establish the relationship between fluorescence/piezoelectric properties and crystal fieldsymmetries with various microstructures. The mechanism of fluorescence/piezoelectric properties in Bi4Ti3O12 crystal doped with rare earth will be clarified based on the experiment results and J-O theoretical calculation, which will guide the development of novel piezoelectrics with high Curie temperature.

探求具有高居里温度、高压电性能以及光致发光特性的多功能材料，对于研制新型高温压电传感器具有重要意义。铋层状结构Bi4Ti3O12体系材料因具有居里温度高、热稳定性好、稀土掺杂可获得良好发光性能而备受关注。本项目拟以Bi4Ti3O12为基质，采用顶部籽晶法生长稀土掺杂Bi4Ti3O12体系单晶。通过优化配方组成、生长参数以及后处理工艺，提高单晶质量与性能；系统研究单晶压电/荧光特性随温度的变化规律。利用稀土离子的发光特征谱，辅以原位拉曼、x-射线衍射等技术，研究温度场作用下单晶沿特定取向的微结构特征（如相结构、畴组态等）及其动态演变过程，探明影响压电/发光性能的微观机制。将实验结果与J-O理论计算作对比研究，建立不同微结构下晶体场对称性与压电/发光性能的本质关系，从而揭示压电/荧光效应的耦合机理，为探索新型高温压电材料提供重要的实验与理论指导。

铋层状结构Bi4Ti3O12（简称：BIT）基压电材料因具有居里温度高、热稳定性好、稀土掺杂可获得良好发光性能而受到广泛关注。本项目通过优化晶体生长制度和工艺参数，获得了高质量的稀土Er掺杂BIT（简称：Er:BIT）单晶，发现Er:BIT单晶的自然显露面是沿(00h)晶面族，并呈现出典型的层状生长特征。Er:BIT单晶的居里温度经测定为673℃，要高于纯BIT单晶的667℃，表明稀土Er掺杂可以有效提高BIT单晶的居里温度。在980nm激光激发下单晶发射出强的绿色荧光，荧光强度要高出同类陶瓷一个数量级。利用Judd-Ofelt理论合理解释了Er:BIT单晶在不同温度下的荧光变色特性；另一方面，项目获得了稀土Sm3+掺杂Bi4Ti3O12-SrBi4Ti4O15、Er3+掺杂Bi4Ti3O12-Bi3Ti1.5W0.5O9共生铋层状多晶陶瓷，发现引入适量稀土Sm3+、Er3+不仅能使多晶陶瓷发射出较强的红橙光、绿光荧光发射，而且有效提高了多晶陶瓷的压电、铁电性能，实现了荧光强度和压电性能的共同提升，表明此类材料中的压电性能与荧光性能存在强的关联性。另外，项目还利用淬火后处理工艺实现了对稀土Er3+掺杂钛酸铋钠基陶瓷的荧光性能与压电性能温度稳定性的调节，为稀土掺杂压电材料的荧光性能调控提供了新途径。同时，项目采用顶部籽晶法生长出具有高机电耦合系数的钛酸铋钠基压电单晶，为下一步获得兼具高压电性能和强荧光效应的多功能材料提供良好的基质材料。在国家自然基金资助下，项目在国内外知名期刊上共发表学术论文11篇，其中SCI收录7篇；申请国家发明专利1项，2020年获得江西省自然科学二等奖1项，并入选2019年度江西省“远航工程”资助对象，申请人晋升教授职称，培养硕士研究生9名，已毕业5名。项目完成结果超过预期目标。