Bi~(3+)或Sm~(3+)掺杂对NaGd(WO_4)_2∶Eu~(3+)荧光粉结构和发光性质的影响

采用水热法制备了白光LED用NaGd_(0.95-x)(WO_4)_2∶0.05Eu~(3+),x Bi~(3+)(x=0,0.02,0.04,0.06,0.08)和NaGd_(0.95-y)(WO_4)_2∶0.05Eu~(3+),y Sm~(3+)(y=0,0.01,0.02,0.03,0.04)系列红色荧光粉,通过X射线衍射仪、扫描电子显微镜及荧光分光光度计等表征手段分析了样品的物相结构、颗粒形貌以及发光性质。结果表明:少量离子掺杂对NaGd(WO_4)_2的晶体结构影响较小,样品均为四方晶系、白钨矿结构的纯相;颗粒形貌呈四方盘状,且粒度均匀,分散性良好,Bi~(3+)或Sm~(3+)的引入使颗粒尺寸由原来的4μm分别增加至5μm和6μm。该系列荧光粉均可被近紫外光(394 nm)有效激发,其最强发射峰位于614 nm处,归属于Eu~(3+)的5D0→7F2电偶极跃迁。掺杂适量的Bi~(3+)或Sm~(3+)可有效提高NaGd_(0.95)(WO_4)_2∶0.05Eu~(3+)荧光粉的发光强度和红光的色纯度,其中Sm~(3+)的引入对其影响更为明显。

Influence of Bi3+ or Sm3+ Doping on Structure and Luminescence Properties of NaGd(WO4)2∶Eu3+ Phosphors

A series of red phosphors NaGd0.95-x(WO4)2∶0.05Eu3+,xBi3+(x=0, 0.02, 0.04, 0.06, 0.08)and NaGd0.95-y(WO4)2∶0.05Eu3+,ySm3+(y=0, 0.01, 0.02, 0.03, 0.04)were synthesized via hydrothermal process.The structure, morphology and luminescent properties of the samples were characterized by X-ray diffraction, scanning electron microscope and fluorescence spectrophotometer, respectively.The results indicate that the crystal structure of NaGd(WO4)2 is almost not changed by doping a small amount of ions, and all samples are tetragonal scheelite-type pure phase.The particles are square plate in shape, relatively uniform and well dispersive.With the introduction of Bi3+ or Sm3+, the particle size increases from the original 4 μm to 5 μm and 6 μm, respectively.The series of phosphors can be effectively excited under near-UV (at 394 nm), and the strongest emission peak is located at 614 nm which corresponds to the 5D0→7F2 transition of Eu3+.In addition, doping with an appropriate amount of Bi3+ or Sm3+ can improve the luminescence intensity and red-light purity of NaGd0.95(WO4)2∶0.05Eu3+ phosphors, especially for Sm3+.