白光LED用宽激发带的稀土硅酸盐基质荧光粉材料

Wide Excitation-Band Particle Phosphors of Rare Earth-Doped Silicate Host for WLEDs

采用稀土复合溶胶的喷雾-热解两步法制备了化学计量为SrxM2-xSiO4xEu^2＋（M=-Ca、Mg、Ba，x=0-2）的用于白光LED的荧光粉。用Van Uitert公式对SrxCa2-xSiO4体系荧光粉中铕离子的激发态带边位置和微结构参数的关系进行了预测计算；对SrxCa2-xSiO4xSrxMg2-xSiO4、SrxBa2-xSiO4碱土正硅酸盐基质荧光粉样品，实测的激发光谱峰值的典型波长在350-460nm的较宽范围内，发射光谱的典型峰值为562nm；在计算不同阳离子的配位数Eu^2＋的发射波长时，把发射波长的计算预测值与实测波长值对比，认为在Sr1．8Ca0．2SiO4：Eu0．04的发光中心中Eu^2＋取代Sr^2＋均位于六配位的Sr^2＋上；荧光颗粒由纳米颗粒（晶）-亚微米的梯次分级自组装结构组成。该稀土硅酸盐基质荧光粉可以作为一种功率型、高亮度和高显色指数的自光LED的重要候选荧光材料。

A particle phosphors with stoichiometric SrxM2-xSiO4 （M=Ca,Mg,Ba, x=0-2 ） for WLEDs （white light emission diode） is prepared by spray-pyrolysis two-step process from rare-earth doped composite sol precursor. Employing the Van Uitert formula, the position of lower d-band edge of Eu^2＋ is calculated from microstructure parameters of SrxCa2-xSiO4 system for prediction. The typical wavelengths of effective excitation of alkaline earth silicate hosts like SrxCa2-xSiO4. SrxMg2-xSiO4 and SrxBa2-xSiO4 phosphors lie in a wider range from 350 to 460 nm, while the typical emission peak locates at around 562 nm. By comparing the calculated wavelengths in different coordinate number of cations with the measured values of samples, we concluded that all substitutions of the luminescent center of Eu^2＋ in Sr1.8Ca0.2SiO4 for the position of Sr^2＋ are in a six-coordinated atomic position. This rare-earth doped silicate phosphor is of a self-assembly, hierarchical structure from nano-crystal or nano- particulate to submicron size in turn. This particle phosphors featured in a wider wavelength range of excitation could be one of the important candidate phosphors for power, high-brightness and higher CRI white LEDs applications.