采用共沉淀方法制备了稀土离子Eu3+, Dy3+, Sm3+掺杂的Ca(Sr, Ba)WO4发光材料,目的是研究金属阳离子改变对稀土离子发光性质的影响。X射线衍射光谱数据表明, CaWO4、SrWO4、BaWO4都是四方晶系I41/a(88)结构, 随着阳离子半径增大, 衍射峰向小角移动。不同温度制备的BaWO4样品X射线衍射光谱数据表明, 温度较低时制备的晶体样品X射线衍射峰较宽; 当制备温度升高后, 晶体样品X射线衍射峰宽变窄。样品的SEM 照片表明, 低温制备的样品晶粒尺寸较小, 约为100~300 nm; 高温制备样品晶粒尺寸较大, 约为2~6 μm。测试了Eu3+, Dy3+, Sm3+掺杂的Ca(Sr, Ba)WO4发光材料的激发和发射光谱。计算了Eu3+掺杂的Ca(Sr, Ba)WO4的J-O强度参数Ωλ (λ=2,4), Ω2值随着阳离子半径增大迅速减小, 经分析它是导致Eu3+掺杂的Ca(Sr, Ba)WO4的发射强度随着阳离子半径增大迅速减弱的原因。然而Sm3+掺杂的SrWO4其他两种晶体相比, 其发射强度反而增强。根据激发光谱和文献报道, 我们认为可能是由于钨酸根离子与稀土离子的能量传递引起的。从Dy3+, Sm3+掺杂的Ca(Sr, Ba)WO4的发射光谱可以看到, 随着阳离子半径增大发射峰蓝移, 发射峰的Stark劈裂减弱。我们用位形坐标图解释了这一现象产生的原因。

Eu3+,Dy3+,Sm3+ doped Ca(Sr,Ba)WO4 phosphors were synthesized by the co-precipitation method in order to investigate the effect of different metallic cations on luminescence properties of rare earth ions. The data of X ray diffraction (XRD) indicated that the crystal structures of CaWO4, SrWO4, BaWO4 belong to tetragonal, I41/a(88) and the diffraction peaks moved towards smaller angle with the increasing diameter of the metal cation. The data of X-ray diffraction (XRD) of BaWO4 synthesized under different temperatures showed that the diffraction peaks were broader under lower synthesized temperature, which can be attributed to the smaller particle sizes (about 100~300 nm seen from SEM morphology) of BaWO4 phosphors under lower synthesized temperature. The emission spectrum and excitation spectrum of Eu3+,Dy3+,Sm3+ doped Ca(Sr, Ba)WO4 phosphors were measured. J-O strength parameters Ωλ (λ=2,4) of Eu3+ ion, were calculated. The data indicated that Ω2 decreased with increasing diameter of the metal cation, which can be used to explain the decrease of emission intensity of Eu3+ doped Ca(Sr, Ba)WO4 with increasing diameter of the metal cation. However, the emission intensity of Sm3+ doped SrWO4 phosphors were more stronger than that of Sm3+ doped Ca(Ba)WO4 which can be explained by the energy transfer between WO2-4 and rare earth ions. It can be seen from the emission spectrum of Dy3+,Sm3+ doped Ca(Sr, Ba)WO4 the emission peaks moved towards shorter wavelength and their bandwidths were reduced, which was explained by the configurational coordinate diagram.