高折射率A2Ti2O7体系透明陶瓷的制备与性能研究

Miniaturization, high imaging quality and increased viewing angle are the develop trend of modern optical devices, and this put forward the urgent need of new high refractive index transparent materials. The present glasses and glass ceramics with high refractive index have high crystallization trend and it’s hard to control, also it’s difficult to fabricate large size optical elements. Combining the high refractive index of TiO2 (about 2.6), cubic structure (in most cases) and high solid solution range of A2B2O7, we propose to fabricate A2Ti2O7 transparent ceramics, expecting to obtain high refractive index (higher than 2.2) optical elements, and providing new choices for high refractive index optical materials. Nevertheless, the study on phase transformation of A2Ti2O7 transparent ceramics (including cubic defective fluorite and pyrochlore structure, monoclinic structure) with the ionic radius of A, and the control of the transition have not been systematically investigated. In this project, A2Ti2O7 powders will be first synthesized and study on the fabrication of transparent ceramics will be carried out. Then, the crystal structure and microstructure of A2Ti2O7 ceramics with the variation of A will be investigated. Meanwhile, the effects of A site doping on energy gap, transmittance range and refractive index will be studied. Finally, A2Ti2O7 transparent ceramics with high transmittance and refractive index are fabricated. This study reveals the relationship of A site element, crystal structure, microstructure and optical properties, and it will provide foundation of further study on transparent ceramics as high refractive index optical elements.

小型化、高成像质量和大视角是现代光学元器件的主要发展方向，迫切需求新型高折射率透明材料。目前的高折射率玻璃和玻璃陶瓷存在控制析晶难且不易制备大尺寸样品等问题。本项目结合TiO2高折射率（约2.6）和A2B2O7体系立方结构及宽固溶范围的特征，希望制备折射率在2.2以上的新型A2Ti2O7体系透明陶瓷。然而，A2Ti2O7体系存在立方缺陷态萤石型、烧绿石和单斜三种晶体结构，随A位离子半径变化其透明陶瓷的相变规律尚缺乏系统研究。本项目首先合成原料粉体并进行透明陶瓷的制备研究。其次，研究随A位元素变化陶瓷晶体结构和显微结构的演变规律与控制原理，以及A位掺杂对能隙宽度、透光范围和折射率等的影响规律。最后制备出高透过率高折射率的A2Ti2O7体系透明陶瓷。通过本项目研究，揭示A2Ti2O7体系陶瓷A位组成-晶体结构-显微结构-光学性能等的依存关系，为透明陶瓷在高折射率光学元件方面的应用研究奠定基础。

针对现代光学元器件小型化、高成像质量和大视角的发展方向，本项目结合TiO2高折射率（约2.6）和A2B2O7体系立方结构及宽固溶范围的特征，提出制备折射率在2.2以上的新型A2Ti2O7体系透明陶瓷，从而替代目前的高折射率玻璃和玻璃陶瓷存在控制析晶难且不易制备大尺寸样品等问题。本项目选取A2Ti2O7（A=Y，La，Gd，Lu）四种体系开展研究工作，首先对粉体合成和陶瓷烧结过程进行系统研究；其次，研究不同A位元素的取代对陶瓷晶体结构、显微结构等的影响规律；最后通过工艺的优化制备出高透过率和高折射率的A2Ti2O7体系透明陶瓷。本项目重点系统研究了共沉淀法和固相法合成粉体以及真空烧结制备Y2Ti2O7透明陶瓷的工艺，研究了制备工艺对陶瓷性能的影响规律，制备出透过率73.0%（1000nm处）、折射率大于2.24（1000nm处）的Y2Ti2O7透明陶瓷，这一结果表明Y2Ti2O7透明陶瓷有望制备成光学元器件，实现其小型化。在其它几种陶瓷的制备过程中，发现固相法制备纯相陶瓷很难，如何有效消除第二相还需要更多的工作；同时，不同A位元素的陶瓷具有不同的烧结行为，其致密化过程和机理还需要更深入地探究。本项目的开展为新型高折射率透明陶瓷光学元器件的材料选择和光学性能开发奠定了科学基础。本项目相关研究成果发表学术论文4篇（均为SCI收录），申请发明专利1项，参加会议进行进展交流2人次，培养毕业硕士研究生1名。