周期性构筑“芯-壳”结构荧光陶瓷及其定向热输运与构效关系研究

Higher brightness, more compact, reduced weight and the static mode have been recognized as promising characteristics of the next generation laser display devices. Overcoming the issue involving thermal transport in the new ceramic phosphors is presently becoming a hot research topic around the world. Generally, heat effect in the composite ceramics designed based on the Maxwell model was partially relieved, nevertheless, thermal transport should be suppressed due to abundant heterogeneous grain boundaries accompanied by the introduction of high thermal conductivity media. In this project, a strategy involving constructing polycrystalline alumina which were continuous and periodically aligned in the YAG:Ce3+ ceramic matrix was conducted, aiming at promoting directed thermal transport and further reducing the thermal flux on the ceramic phosphor. A coaxial electrospinning technic was applied to prepare the “core-shell” structured Al2O3@YAG: Ce3+ fibers and highly aligned fiber-precursor membranes. The sintering of composite ceramics with dense and periodically arranged “core-shell” architecture was followed using current-activated, pressure-assisted densification (CAPAD, often called spark plasma sintering, SPS). The thermal conductive path associated cross-sectional dimension and spatial density effects were discussed, the influence of heterogeneous grain boundary properties on the thermal transport was studied. Based on these experimental rules, a structure-activity relationship between ceramics’ macroscopic/ microcosmic structures and the thermal transport efficiency was constructed. The accurate control of periodical structures and modulation of microstructures of the heterogeneous grain boundaries were also conducted, revealing the controlling mechanisms of thermal transport process. The contribution of the improved thermal transport on the luminescence characteristics and its intrinsic mechanism were preliminarily discussed. The present study is expected to provide guidance for the design of high-performance ceramic phosphors, and further paving the way for flexible design, improved quality and boosted practicality of the laser display devices.

解决荧光陶瓷“热输运”难题是激光显示器件向高亮、紧凑及静态模式方向发展的关键。目前在荧光陶瓷中引入高热导介质部分缓解了热效应，但异质晶界结构对热的定向输运形成阻碍。本研究以YAG:Ce为荧光主体，拟通过在其中构筑连续和周期性排布的多晶氧化铝通道增强定向热输运，降低荧光主体热流密度。采用同轴共纺静电纺丝制备高度取向的“芯-壳”结构Al2O3@YAG:Ce纤维前驱体膜，结合压力辅助放电等离子体烧结技术获得“芯-壳”周期排布的致密荧光陶瓷；讨论热输运通道截面尺寸及空间密度效应，探讨异质界面耦合行为对热输运效率的影响规律，建立宏观/微观结构与热输运效率的构效关系；开展周期结构精准调控和异质界面显微结构优化研究，揭示热输运过程控制机制；初步阐明新结构陶瓷热输运效率与发光协同增强机制。上述研究有望为高性能荧光陶瓷的设计提供指导，为提高激光显示器件设计的自由度、促进器件向高品质和实用化方向发展奠定基础。

解决荧光陶瓷“热输运”难题是激光显示器件向高亮、紧凑及静态模式方向发展的关键。本项目以YAG:Ce或Al2O3/YAG:Ce为荧光主体，拟通过在其中构筑连续和周期性排布的多晶氧化铝通道增强定向热输运，降低荧光主体热流密度。发展了DLP光固化3D打印与注凝成型相结合的复合陶瓷制备技术，系统开展了Al2O3及YAG陶瓷浆料的组分设计和性能调控研究，获得了适用于Al2O3、YAG和Al2O3/YAG:Ce复相荧光陶瓷粉体的高性能陶瓷浆料及光固化工艺参数，成功制备出了高导热Al2O3陶瓷呈阵列排布的周期性“芯-壳”结构Al2O3-Al2O3/YAG:Ce复合荧光陶瓷，对Al2O3-Al2O3/YAG:Ce复合陶瓷的成型工艺和异质界面结构进行了调控研究，实现了Al2O3（导热通道）与Al2O3/YAG:Ce（荧光主体）界面的强耦合；开展了不同“芯”-“壳”占比的周期性结构复合荧光陶瓷的制备及发光与热学性能研究，讨论了“芯-壳”结构复合荧光陶瓷的结构参数与发光性能和热管理性能之间的关联；开展了基于新型结构荧光陶瓷的发光模块的制备，周期性“芯-壳”结构复合荧光陶瓷在70.3 W/mm2功率密度激光光源辐照下未发生结构失效，表明复合荧光陶瓷的激光耐受特性得到显著提升；进一步地开展了“类光腔”结构复合荧光陶瓷的制备，通过改性氧化铝提升了“壳”的可见光反射特性、并保留了其热扩散效率，抑制了荧光主体和导热通道异质界面的光串扰，同时依靠壳结构对泵浦光源的多次反射，强化了泵浦光源与荧光主体之间的相互作用，使得新型类光腔结构复合荧光陶瓷的荧光转化效率和发光稳定性得到同步提升；借助有限元仿真计算方法并结合实验验证对热输运机制进行了探讨研究，提出“异质结构温差驱动”的定向热输运增强机制，为功率型电子元器件用热管理陶瓷/陶瓷基复合材料开发提供新的思路和方法。