黄绿色荧光粉CaWO_4∶Pr^(3+)的发光性质与晶体场分析

Luminescent Properties and Crystal-Field Analysis for Novel Yellow-Green Phosphor CaWO_4∶Pr^(3+)

采用共沉淀法成功制备了新型黄绿色荧光粉Ca1-x WO4∶xPr3+(摩尔分数x=0.1%,0.3%,0.5%,0.7%)。通过X射线衍射(XRD)、扫描电镜(SEM)和荧光光谱等测试手段进行了结构、形貌和光致发光研究。结果表明:黄绿色荧光粉CaWO4∶Pr3+具有四角白钨矿类结构,空间群为I41/a,其表面形貌较规则、粉粒大小为5~20μm。CaWO4∶Pr3+可被487nm蓝光有效激发,其发射光谱由一系列锐谱组成,分别位于530nm(3P1→3 H5)、547nm、555nm(3P0→3 H5)、602nm(1 D2→3 H4)、618nm、637nm(3P0→3 H6)和648nm(3P0→3F2)。当摩尔分数达到0.5%时样品光致发光最强。样品的色坐标为(x=0.39,y=0.55),表明所发光为黄绿光。为了更好的理解CaWO4∶Pr3+的荧光谱,建立了包括4f2电子组态的自由离子和晶体场相互作用的91×91阶能量哈密顿量矩阵,在理论上合理地解释了Pr3+离子在CaWO4晶体中四角(S4)Ca2+晶位的光谱数据,所得理论值与实验结果吻合较好。

Pr3＋-doped cadmium tungstate yellow-green phosphors Ca1-xWO4xPr3＋ （mole fraction x=0.1%, 0.3%, 0.5%, 0.7%） are successfully synthesized by the co-precipitation method. The crystal structure, morphology and photoluminescence （PL） properties are characterized by X-ray diffraction （XRD）, scanning electron microscope （SEM） and fluorescence spectrometer. The results show that CaWO4：Pr3＋ has a tetragonal sheelite structure with space group I41/a. The SEM image shows that the grains are irregular with sizes ranging from 5 to 20 μm. The emission spectrum of the CaWO4：Pr3＋ phosphor is characterized, its peaks locate at 530, 547，555, 602, 618, 637 and 648nm corresponding to the 3P1→3H5, 3P0→3H5, 3P0→3H5, 1D2→3H4, 3P0→3H6, 3P0→3H6 and 3P0→3F2 transitions of Pr3＋, respectively. The strongest one appears at 648 nm when is excited by 487 nm which matches well with blue chips. The optimized concentration of Pr3＋ is 0.5% for the highest PL emission intensity. In addition, to understand the fluorescent spectra of as-synthesized phosphors, a complete 91×91 energy matrix is built by an effective operator Hamiltonian including free ion and crystal field interactions. The fluorescent spectra for Pr3＋ ion at the tetragonal （S4） Ca2＋ site of CaWO4 crystal are calculated from a full diagonalization （of energy matrix） method. The fitting values are in good agreement with the experimental data.