卤磷灰石自激活荧光粉的可控合成及其缺陷发光机理

Intrinsic defect-related self-activated phosphor is an important part of inorganic luminescent materials. A deep insight into the defect formation process and electronic structure of defective supercell is essential for developing novel self-activated phosphors. A series of halo-apatite type M5(PO4)3X (M = Ca, Sr, Ba; X = F, Cl, Br) compounds will be synthesized in this project. The intensity and color of the self-activated luminescence in halo-apatite host lattices can be tuned by surface-annealing conditions and the solid solution compositions. A combination of experimental and theoretical characterizations will be employed to gain a comprehensive understanding of the influence of the synthetic atmosphere condition as well as the structural disturbance in solid solution crystals on the possible defect formation and defect concentration. The experimental characterizations include electronic paramagnetic resonance (EPR), X-ray photoelectron spectroscopy (XPS) and optical spectra, et al. The theoretical calculations are performed based on density functional theory (DFT). The defect energy level distribution and the coupling relationship with host band structure are to be investigated. The local defect structural relaxation and its effect on the charge transition mechanism within the defect levels will also be explored. After this project, a new experimental and theoretical methodology for rational design of defect-related luminescent materials is expected to be established, and a series of novel self-activated color-tunable phosphors with high quantum efficiency are going to be provided.

本征点缺陷调控的自激活荧光粉是一类重要的无机发光材料。因此，深入了解本征点缺陷的形成过程与缺陷晶胞的电子结构，对发展新型自激活荧光粉具有重要意义。本项目拟以卤磷灰石型M5(PO4)3X (M = Ca, Sr, Ba; X = F, Cl, Br)化合物为模型，通过控制合成条件和固溶组分比例，调控卤磷灰石自激活缺陷发光强度和发光颜色。采用EPR、XPS、光谱等实验表征技术，结合密度泛函理论计算，深入分析合成气氛条件、固溶体晶体结构扰动对缺陷形成类型和缺陷浓度的影响，阐述能带结构与缺陷能级布局、局域缺陷结构驰豫与缺陷能级电荷跃迁机制的耦合关系。本项目将为缺陷调控发光材料的设计合成提供新的实验方法和理论支持，并合成系列新型可见光颜色可调的高量子效率自激活荧光粉。

本征点缺陷广泛存在于固体材料中，制约材料的物理性质。稳定控制缺陷类型和浓度，精准调控材料光电性质，是一种开发新型光电材料的有效途径。本项目以卤磷灰石型化合物为研究对象，采用实验和理论计算相结合的研究方法，系统探究了还原气氛下合成的M5(PO4)3X (MPOX; M = Ca/Sr/Ba, X = F/Cl/Br)中本征缺陷类型、电子结构和光电性质，设计并控制合成了一系列阴离子空位缺陷自激活发光材料。在短波紫外（~250 nm）激发下，MPOX (X = Cl/Br)具有覆盖可见光区的超宽带发射，发光颜色随M阳离子半径增大在蓝紫光→橙光范围内连续可调；M阳离子固溶组成有利于提高发光强度，Sr3Ba2(PO4)3Cl、Sr2Ba3(PO4)3Br与Sr3Ba2(PO4)3Br的发光内量子效率超过90%。研究结果表明MPOX的超宽带发射来源于氧空位缺陷（VO），大的Stokes位移来源于VO–[PO3]3-局域缺陷结构激发态和基态较大的结构弛豫，发射波长的连续可调性红移来自于基质晶体禁带宽度的逐渐降低，固溶体发光增强则与固溶晶体晶格扰动增强、缺陷形成能降低、缺陷浓度增大有关。本项目系统总结了多阴离子体系卤磷灰石型化合物中的阴离子空位缺陷形成规律和相关缺陷发光机理，为阴离子缺陷调控和缺陷材料设计合成提供了良好的理论基础，并获得一系列新型高效、节能环保的阴离子空位缺陷自激活发光材料。