硅氧四面体中阳离子的组合替换对荧光粉微结构和发光性质的影响机制

In recent years, silicate phosphors have attracted increasing attention on use for the white LEDs, which is attributed to low-cost raw materials, simple production process, high stability, good optical properties, etc. We will optimize the composition of silicate phosphors by the substitution of B3+/Al3+—P5+ for Si(1)4+–Si(2)4+ in silicon oxygen tetrahedrons, which is due to alternative ions of silicon oxygen tetrahedrons. To investigate comprehensively the change rule of crystal structure of silicate phosphors, the size of silicon oxygen tetrahedron is reduced or enlarged by changing the amount of B3+/Al3+—P5+. According to the contrastive analysis of theoretical data and experimental data of crystal parameter, the relationship between silicate crystal parameter and cationic compositions is investigated. We will study the relationship between the crystal parameter of silicate phosphors and energy splitting of outmost orbiting electron of activators with different electron transition. Energy transfer of activators is investigated with varied crystal parameter of silicate phosphors. Then, anionic group effect on phosphor is comprehensively investigated. The silicate phosphors with high performance will be obtained by changing composition of phosphors and production process parameters. The research is to improve the luminescence mechanism of phosphors, and offer help to prepare new phosphors.

硅酸盐荧光粉具有原料低廉、工艺简单、稳定性高、光学性质好等优点，成为白光LEDs中重点研究的粉体之一。本项目利用硅氧四面体中元素的互替性，拟从B3+/Al3+—P5+替换Si(1)4+—Si(2)4+入手，调整硅酸盐荧光粉的组成；在保持价态平衡的前提下，通过调控B3+—P5+和Al3+—P5+的掺入量，来增大或者减小硅氧四面体的尺寸，将大尺寸替换效应和小尺寸替换效应归纳统一，研究荧光粉结构的变化规律；对比分析晶格参数的理论计算值和实际测量值，建立阳离子组合替换对硅酸盐结构的调控模型；通过调控硅酸盐的晶体结构参数，分析不同电子跃迁形式的激活离子的外层电子的能级劈裂程度，研究激活离子之间能量传递效率的高低和速度的快慢，探索发光机理中的阴离子基团效应；通过调整基质组成和优化制备工艺参数，制备出高效硅酸盐荧光粉。本项目的完成将有利于深化荧光粉的发光机理，为新材料的研究开发提供理论和实践基础。

本项目从探索新型的磷铝酸盐和磷硼酸盐荧光粉入手，制备了稀土离子掺杂的Li2Sr2Al(PO4)3、Li6Na3Sr14Al11P22O90、Ba3AlPO7和Ba3(ZnB5O10)PO4荧光粉，分析荧光粉的结构和光学性质。实验结果显示磷铝酸盐和磷硼酸盐荧光粉具有强的可见光输出和良好的荧光热稳定性，可用作白光LED的光转换材料。.在此基础上采用阴离子基团替换的方法优化传统的硅酸盐荧光粉：[AlPO8]2-替换[Si2O8]2-优化Sr3SiO5:Ce3+、Sr3SiO5:Eu2+、Sr3SiO5:Ce3+, Eu2+、Ca3Si2O7:Eu2+、Ca3Si2O7:Eu3+荧光粉；[BPO8]2-替换[Si2O8]2-优化Ba2SiO4:Dy3+、Ba2SiO4:Eu3+荧光粉。实验结果显示大部分硅酸盐与AlPO4或BPO4形成有限固溶体，当AlPO4或BPO4浓度超过20mol%，易出现杂相。少量AlPO4和BPO4的掺入不会改变晶相，但会引起荧光粉晶格参数的改变，导致发光离子所处晶体场的强度发生变化，进而影响到发光离子的发光强度和发光颜色。Ca2.99Si2O7:0.01Eu2+的发光为橘红色，然而Ca2.99Si1.96(AlP)0.2O7:0.01Eu2+的发光为黄绿色。Sr2.94Si0.94(AlP)0.03O5:0.06Tb3+的发光强度却是Sr2.94SiO5:0.06Tb3+的3.7倍。发光强度提高的原因主要有两个：一是多组分使得荧光粉的结晶中自由度数增多，样品结晶温度降低，提高了样品的结晶度；另外一个是改变了发光离子所处的晶体场环境。发光颜色的改变原因主要有两个：一个是晶体场的场强发生改变；另外一个是处于不同发光中心的发光离子数发生变化。 .为了进一步探讨发光机理，在BaAl2O4荧光粉中进行[MgSi]与[Al]的互换，在CaAl2Si2O8荧光粉中实现[NaSi]与[CaAl]的互换，在Ba7(BO3)3(SiO4)(Cl, Br)中实现[Cl-]与[Br-]的互相替换。离子基团的互相替换同样引起荧光粉发光强度和发光颜色的巨大改变。