真空合成稀土硫氧化物发光材料机理研究

Owing to their wide potential applications in such fields as lighting, displays and optical storage, the preparation of rare earth oxysulfide phosphor has been studied extensively. Aiming to solve the problems such as high synthesis temperature and large particle size, etc. in traditional solid state reaction method, the scheme of low-temperature solid state reaction in vacuum for the preparation of rare earth sulfide phosphors is proposed in this project. The inhibition of sulfur volatilization is commenced and the reaction process in vacuum is studied to elucidate the vacuum synthesis mechanism. Influence of various factors such as vacuum degree on crystal structure, crystal growth and luminescence properties of the phosphor is studied in order that the vacuum firing schedule is determined and the grain refining mechanisms under vacuum is also explored. The effect of impurities on crystal growth and the formation mechanisms of impurity phase are investigated. The influence of impurity disturbance and lattice distortion on luminescence properties is discussed. Therefore, the behavior of crystal particle size and micro-structure change on regulation and enhancement of luminescence is explored. Geometry, electronic structure and spectroscopic properties of rare earth ions activated gadolinium oxysulfide are simulated through first principles calculation to clarify the energy transfer mechanisms of impurity atoms in host at atomic level. Consequently, the effect of vacuum on the process of crystal growth and the change of luminescence mechanisms arising therefrom is confirmed in theory. The investigations could enrich the preparation method and theoretical basis of rare earth luminescent materials. Meanwhile, this project may also provide theoretical significance and practical values of the structural and performance optimization.

稀土硫氧化物在照明、显示、光学存储等领域具有广泛应用而成为研究热点。本项目提出真空低温固相反应制备该材料的技术思路，以解决传统的高温固相反应合成温度高、产物颗粒尺寸大等问题，重点研究原料混合物在真空下固相反应历程，阐明该反应过程的真空合成机理；研究真空度等影响因素对材料的晶体结构、晶体生长及其发光性能的影响，确定适宜的真空焙烧制度及晶粒细化机理；研究真空下杂质原子对晶体生长的作用机制及杂相形成机理，探讨杂质微扰及晶格畸变对发光性能的调控机制，得到粒径尺寸与晶体内部微观结构对发光性能的调控及增强效应的影响规律；对不同稀土离子激活的硫氧化钆的几何结构、电子结构及光谱性质进行第一性原理计算，在原子水平上考察杂质原子在基质中的能量传递机制，从理论上证实真空对晶体生长过程的作用机理以及由此导致的发光机理变化。研究结果将充实稀土发光材料的制备及理论基础，对发光材料的结构和性能优化与具有重要的理论意义。

该项目为解决传统的高温固相反应制备稀土硫氧化物发光材料过程中存在的合成温度高、产物颗粒尺寸大等问题，重点研究原料混合物在真空下固相反应历程，对材料的晶体结构及发光性能进行系统研究，获得微观结构调控以及性能优化的基础数据，具体如下：.（1）确定了稀土硫氧化物发光材料的真空合成机理。热分析和热力学计算结果表明，固相法合成稀土硫氧化物发光材料分两个阶段进行，第一阶段为单质S与Na2CO3反应，第二阶段反应为Na2SX与Gd2O3反应。 通过对可能的反应进行热力学计算发现Gd2O3与Na2SX (X = 2-4)可以反应，但是和Na2S不能发生反应；动力学研究结果表明，常压条件下，第二阶段和第三阶段反应的活化能值分别为72.84 kJ/mol和232.47 kJ/mol。真空条件下，第二阶段和第三阶段反应的活化能值分别为64.30 kJ/mol和210.70 kJ/mol。发现真空条件下反应的活化能值小于常压条件下反应的活化能值，说明真空条件有利于稀土硫氧化物的生成，且第三阶段反应的机理控制步骤不同。.（2）采用低温真空条件下的固相反应制备出稀土硫氧化物发光材料，XRD、SEM、TEM及发光光谱研究表明，具有亚微米级到纳米级颗粒尺寸，切表现出优异的上下转换及颜色可调性质。.（3）在实验研究的基础上，计算不同类型杂质原子及晶格缺陷对材料结构稳定性、电子结构和光谱性质的影响，通过计算能级图、态密度、差分电荷密度、原子布居、吸收光谱等，从理论上分析晶体内部的微观结构变化而导致的不同的发光机理，证实真空合成过程中Li+、Bi3+及其他稀土金属离子在Gd2O2S微结构的占位情况及Gd2O2S:Re的晶体生长机制。.（4）发表论文9篇，其中SCI检索6篇，获专利授权3项，申请专利3项，参加学术会议3次，团队成员中晋升教授1人，晋升高级工程师1人，博士后出站1人，指导在读硕士研究生3人。