阳离子取代诱导稀土掺杂硅/磷酸盐体系晶体结构的微观改变及发光性质调控

By changing the crystal structure to control the luminescence properties of rare earth ion-doped silicate/phosphate materials has been widely concerned. However, many cationic / anionic substitution induced luminescence-tunable mechanisms are unclear because the physical properties associated with the electronic structure of rare earth 4f5d transitions have not been deeply investigated. Herein, the project employs cationic substitution strategies including A+-P5+/B2+-Si4+ and B2+-P5+/C3+-Si4+ (A are alkali metal, B are alkaline earth metal, C are Y, La, Gd) to tune and optimize the luminescence properties of silicate/phosphate-based luminescence materials. The fine structure characterizations including a series of synchrotron radiation technologies are used to determine the changes of coordination environment, valence state and site-occupancy of activator ions at different lattice sites with the cationic substitutions. These structural changes can influence the 5d energy level splitting, nephelauxetic effect and covalency of rare earth ions. On the basis of the above analysis, we can explore the relationship between structural changes and tunable photoluminescence properties based on 4f-5d electronic structure, and establish the relationship of microstructure and macroscopic luminescence properties. These investigations can reveal the cationic substitutions induced luminescence-tunable mechanisms in silicate/phosphate luminescence materials and complete the "structural changes - tunable luminescence" theoretical system. Finally, the proposed luminescence mechanisms not only provide a theoretical basis for the directional optimization of luminescence properties and production of new luminescent materials, but also promote the rare earth doped luminescence materials to be further widely applied in white LED lighting fields.

通过晶体结构的改变调控稀土掺杂硅/磷酸盐材料的发光性质已被广泛关注。但由于对稀土4f5d电子结构的物性关联认识不深，导致很多阳/阴离子取代诱导的发光调控机理不清楚。本项目拟通过A+-P5+/B2+-Si4+和B2+-P5+/C3+-Si4+（A为碱金属，B为碱土金属，C为Y, La, Gd）等阳离子取代来调控和优化稀土离子掺杂硅/磷酸盐材料的发光性质。通过同步辐射等一系列晶体结构精细表征判断不同晶体格位上激活剂离子周围微观结构配位环境、价态和占位随阳离子取代含量的变化，分析这些变化对稀土离子5d轨道能级劈裂、电子云重排效应及晶体共价性的影响。从4f-5d电子结构出发，建立微观结构与发光性能的关系，揭示阳离子取代诱导的硅/磷酸盐发光体系中发光调控的机理，完善“结构改变-发光调控”的理论体系。本项目的开展可以为定向优化和制备新颖稀土发光材料提供理论基础，促进其在白光LED照明等领域的广泛应用。

通过晶体结构的改变调控稀土掺杂硅/磷酸盐材料的发光性质已被广泛关注。但由于对稀土4f5d电子结构的物性关联认识不深，导致很多阳/阴离子取代诱导的发光调控机理不清楚。为了深入理解晶体结构改变对发光性能的影响，本项目从三个方面开展了工作：（a）寻找具有高对称晶体和晶格结构，实现稀土Eu2+离子的有效掺杂及窄带发光，并系统总结实现窄带发光对晶体结构的要求。（b）设计组分取代或能量传递策略，实现对发光性能的大范围调控，结合密度泛函计算和精细的微观晶体结构表征，揭示晶体结构和发光性能的物性关联。为以后发光性能调控提供理论指导。（c）设计组分取代或者制造缺陷，实现荧光粉材料的反热猝灭性能，提高荧光粉在白光LED的应用。在上述研究工作中，通过同步辐射等一系列晶体结构精细表征判断不同晶体格位上激活剂离子周围微观结构配位环境、价态和占位随阳离子取代含量的变化，分析这些变化对稀土离子5d轨道能级劈裂、电子云重排效应及晶体共价性的影响。从4f-5d电子结构出发，建立微观结构与发光性能的关系，揭示阳离子取代诱导的硅/磷酸盐发光体系中发光调控的机理，完善“结构改变-发光调控”的理论体系。同时将提出的“结构改变-发光调控”理论体系拓展到非稀土离子Bi3+掺杂的多元氧化物体系中，探讨提出的机理的普适性。本项目的开展为定向优化和制备新颖稀土发光材料提供理论基础，促进其在白光LED照明及背光显示等领域的广泛应用。