单一相荧光粉基质体系钡镥硅氧化物相图及热力学

The novel single-phase full-color phosphor suitable for UV-LED excitation is expected to apply in white LEDs due to its low color temperature, high color rendering index, adjustable color coordinates and high luminous efficiency. However, recent work to optimize material preparation and promote luminescence of the single-phase full-color phosphor encountered some difficulties due to the lack of phase relationship and thermodynamics of BaO-Lu2O3-SiO2 matrix system. Actually, it is very difficult to find the real phase equilibria at low and high temperature in BaO-Lu2O3-SiO2 system and its sub-systems due to slow diffusion rate within the solid phases and the difficulty to measure liquidus line. This project aims to slove these problems. On one hand, high-quality phase diagram especailly in the low temperature region will be contructed by the use of a series of advanced methods, such as obtain dry but uniform specimens by the Sol-Gel reaction of metal alkoxides,acquire the heating times of phase balance by microstructure observation and XRD tests equiped with a new sample-preparation-method, and determine the religions of solid solution accurately by measurement of lattice constants and the calculation of limiting slope. On the other hand, the Modified Quasi-chemical Model in the Pair-approximation for Short-range Ordering is combined with the Ionic Two-sublattice Liquid Model to optimize and calculate of the system and its subsystems. The new model in good agreement with the actual characteristics of the high temperature solution will fit well with the liquid miscibility gap and invariant point of binary systems, then enhance the compatibility with ternary system and finally obtain self-consistent phase diagrams and thermodynamic data, the approach to study phase equilibria, and thermodynamic model and its established method. The study will offer theoretical basis for the further research and performance optimization of the novel phosphor,but also provide new ideas for the phase diagram and thermodynamic research on related metallurgical systems.

新发现的紫外光激发单一相白光荧光粉具有低色温、高显色、色坐标可调、较高光效等优点而显现出重要的应用前景，但其基质体系钡镥硅氧化物相图及热力学知识严重缺乏阻碍了材料制备工艺改进和性能提升。针对该体系相图实验低温下固相内的扩散速度慢、高温液相线难测准而导致观测不到真正平衡组成的核心问题，本项目采用金属醇盐的Sol-Gel 过程获得均匀性试料；结合微结构观测和配备"撒样法"的相态XRD确定平衡加热时间；由点阵常数和极限斜率确定和评估固溶体等，提升相图低温区域准确性；在此基础上，将改良的短程有序-对近似-似化学模型与双亚晶格模型结合，建立更符合溶液内部物理特征的高温液相新模型，优化计算高温区域溶解度间隙等关键部分，以至增强对高元系的兼容能力。研究获得的自洽相图与热力学、低温相平衡研究方法、热力学模型及建立方法，将为白光荧光粉的性能优化提供急切需要的理论基础，同时也为冶金领域相关研究提供有益借鉴。

新发现的紫外光激发单一相白光荧光粉具有低色温、高显色、色坐标可调、较高光效等优点而显现出重要的应用前景，但其基质体系钡镥硅氧化物相图及热力学知识严重缺乏阻碍了材料制备工艺改进和性能提升。本课题通过“实验测量与理论计算相结合”的研究方式，在提升相图实验精度的同时，对BaO-Lu2O3、 BaO-SiO2、Lu2O3-SiO2、BaO-Lu2O3-SiO2等体系热力学数据进行反复评估，重点解决了较低温度相平衡、高温液相模型建立、液相溶解度间隙区域确定等关键问题，得到基于短程有序特征的兼容性强的离子双亚晶格模型及相应的模型建立方法，模型表达式分别为(Ba2+)P(O2–,SiO44–,SiO20)Q、(Lu3+)P(O2-,SiO20)Q、(Ba2+,Lu3+)P(O2-)Q、(Ba2+,Lu3+)P(O2–,SiO44–,SiO20)Q。获得了BaO-SiO2、BaO-Lu2O3和Lu2O3-SiO2三个边二元系相图，并通过外推上升得到BaO-Lu2O3-SiO2三元系相图，最终获得了钡镥硅氧化物体系自洽一致的相图和热力学函数；同时，从研究得到的相图中，分别提取了Ba2SiO4和Ba3Lu4O9等中间化合物的相态信息，指导合成了MxCa2-xSiO4:Ce3+,Al3+(M=Mg,Sr,Ba)、γ-CaSiO4:Ce3+,Al3+、Ba3Lu4O9:Er3+,Yb3+、SrLu2O4:Ho3+,Yb3+、SrLu2O4:Ho3+,Yb3+,Li+等荧光材料，并通过对荧光材料结构、形貌、发光性能的深入研究，得到了不同离子掺杂和基质结构之间的作用机理，最终优化得到了一系列发光性能优异、具备潜在应用价值的荧光材料。