掺杂Eu^(3+)离子LaPO_4的合成及其发光特性研究

Synthesis and Luminescent Properties of Eu^(3+)-doped LaPO_4

采用固相反应法合成了掺杂Eu3+离子的LaPO4,并用X射线粉末衍射对其结构进行了表征。XRD数据经计算机处理表明:LaPO4属单斜晶系,晶胞参数a=6 84 ,b=7 08 ,c=6 46 ,β=103 85°,属P21/n(No 14)空间群。测定了其激发光谱和发射光谱,光谱数据表明:在掺杂Eu3+离子的LaPO4荧光体中,基质LaPO4的电荷迁移激发态的能量能有效地传递到Eu3+离子,说明基质LaPO4本身对发光有贡献。位于592,612nm附近的2个发射峰均出现劈裂现象,即有2个5D0→7F1(590,594nm)、2个5D0→7F2(610,614nm)发射峰,说明掺杂的Eu3+离子在LaPO4晶体中有着不相同的配位环境,推测Eu3+离子处于D2d或D3对称格位。

The Eu3+doped LaPO4 phosphor was prepared with the conventional solidstate reaction method. Stoichiometric amounts of (NH4)2HPO4 and H3BO3 were milled and fired in air at 900℃ for 2h, and washed thoroughly with distilled water. The white powder, BPO4, was dried at 110℃ in an oven for 3h. Stoichiometric amounts of La2O3, BPO4, Eu2O3 and Li2CO3 were milled and subsequently fired in air at 900℃ for 2h, and treated with 2mol·L-1 HNO3 and 10% NH3·H2O for 12h, washed thoroughly with distilled water. The product was dried at 110℃ in an oven for 3h, and finally stored in a desiccator until use. The Eu3+doped LaPO4 phosphor was characterized by powder Xray diffractometry. According to our measurements with Xray diffraction, this material belongs to monoclinic crystal system with its lattice constants: a=684?,b=708?,c=646?,β=10385°, it is consistent with space group P21/n (No14). The excitation and emission spectra were measured. The luminescence properties of Eu3+doped LaPO4 and energy transfer mechanism were discussed. Under 393nm radiation excitation, the emission spectra of LaPO4∶Eu consists of the sharp line emissions in the range of 500～720nm from the transitions of electrons in 4f shell of Eu3+. The main peak at 612nm can be ascribed to the 5D0→7F2 transition of Eu3+, it shows a strong red emission, and the 5D0→7F2 transition emission splits to 610, 614nm. The peak at 592nm can be ascribed to the 5D0→7F1 transition, Eu3+, it splits to 590, 594nm also. The excitation spectra of Eu3+5D0→7F2 transition emission have two parts, the wide band between 200～300nm and sharp lines between 300～600nm. The wide band includes both charge transfer excitation of PO3-4 and charge transfer excitation of Eu3+, and the sharp lines originate from Eu3+ ff electron transitions. The strong evidence from excitation spectra, emission spectra of this system showed that there is the energy transfer from host lattice to activator in the process of luminescence.