基于电荷迁移带带边移动的光学温度探测新机制研究

Temperature sensing with traditional contact thermometers is difficult for many special cases due to the limitations in spatial resolution, response speed, and so on. The non-contact temperature sensing based on the temperature dependent optical property of the rare earth ions doped luminescent materials has gained most attention in recent years. How to further improve the temperature sensitivity of the temperature sensing materials is a great challenge needing to be solved. Exploring new mechanisms is an effective pathway to obtain temperature sensing materials with high sensitivity. In this project, we will study the temperature dependent properties of the charge transfer band (CTB) edge in some materials possessing CTB excitation and reveal its physical mechanisms. And then, the host materials with more remarkable shift of the CTB edge with temperature variation will be found out accordingly. Novel temperature sensing strategies will be designed based on the remarkable variation of the excitation in the tail of the CTB with temperature variation combined with the thermal population of the adjacent energy levels of some rare earth ions. The relationships between temperature and excitation intensity ratio, fluorescence intensity and fluorescence intensity ratio will be studied. And based on the proposed strategies, temperature sensing materials with higher temperature sensitivity are expected to be obtained. The implementation of this project is helpful for further understanding the temperature property of the CTB, enriching optical temperature sensing mechanisms and can provide novel ideas for obtaining high sensitive temperature sensing materials.

传统的接触式温度计在空间分辨、响应速度等方面受到极大限制，难以满足诸多特殊环境下的测温需求。近年来，基于稀土发光材料光学响应的非接触式温度传感受到了广泛的关注，如何进一步提高光学测温材料的温度灵敏度成为目前亟待解决的关键问题。开展对光学温度探测新机制的研究是获得具有高温度灵敏度的测温新材料的有效途径。本项目拟从具备电荷迁移带激发的材料入手，通过研究电荷迁移带带边随温度的变化规律，明确温度改变导致带边移动的物理机理，从而找出带边随温度变化移动更为剧烈的基质材料。利用其带尾处激发效率随温度的剧烈变化，结合某些稀土离子相邻能级之间的热耦合特性，设计新型测温策略，研究激发强度比、荧光强度及荧光强度比的温度依赖关系，以期制备出具有更高温度灵敏度的测温材料。本项目的实施可以加深对电荷迁移带温度特性的认识，丰富光学测温机制，为获得高灵敏的测温材料提供新思路。

基于物质光学响应的光学温度探测凭借其非接触式探测模式、快速响应、高空间分辨等优点，可以用来弥补传统接触式温度计的不足。探索新型光学测温机制以获得高灵敏的光学测温材料，对于非接触式温度探测的实用化具有非常重要的推动作用。本项目从温度诱导电荷迁移带带边移动出发，结合稀土离子热耦合能级的热耦合特性、热占据、荧光温度猝灭等，探索新型光学测温机制，构建基于激发强度比、荧光强度以及双发光中心荧光强度比的新型高灵敏测温方案。取得的主要结果：基于温度诱导电荷迁移带带边移动导致带尾处激发强度增强，结合稀土离子热耦合能级（Er3+的2H11/2和4S3/2、Sm3+的4F3/2和4G5/2）的热耦合特性或Eu3+的5D1能级的热占据，设计了基于荧光强度的高灵敏测温方案；结合Eu3+的基态与邻近激发态能级之间的热耦合，利用电荷迁移带带尾处激发强度与从Eu3+基态跃迁激发强度之间的相反变化，设计了基于激发强度比的测温方案；成功引入另外一种具有相反荧光温度依赖特性的发光中心，在Eu3+掺杂的YV0.3P0.7O4固溶体中引入Tb3+，在Eu3+掺杂的YVO4中引入Tm3+，实现了两种发光中心相反的荧光变化趋势，构建了基于双发光中心荧光强度比的高灵敏测温方案，所得最高相对灵敏度可达4.6% K-1。其科学意义在于：加深了对温度诱导钒氧电荷迁移带带边移动的理解；从该特性出发，我们提出了一些新型的高灵敏光学测温机制，获得了一些具有潜在应用价值的非接触式光学温度探测材料；为探索具有更高灵敏度和潜在应用价值的光学测温材料或光学测温机制，拓宽了思路。