纳米GdPO_4∶Eu^(3+)的合成和光谱特性

Synthesis and Spectra Properties of Nanocrystalline GdPO_4∶Eu^(3+)

采用EDTA二钠盐参加的共沉淀方法制备出纳米GdPO4∶Eu3+,利用X射线衍射,荧光光谱和电镜等测试手段对GdPO4∶Eu3+的相结构和发光性质进行了研究。XRD图谱结果表明700℃合成了纯的具有单斜晶系、独居石结构的纳米GdPO4∶Eu3+。根据Scherrer公式计算,700,800℃热处理后样品的一次颗粒度分别为18,40 nm左右。激发光谱和发射光谱的研究表明,电荷迁移态和Eu3+的特征发射峰的强度随GdPO4∶Eu3+纳米粒子的增大而增强。在较小的纳米粒子中,存在结构扭曲的现象,315 nm激发下的发射光谱研究表明,Gd3+和Eu3+具有较好的能量传递。

Rare earth doped nanocrystalline phosphors have attracted great interest. The main work concerns the synthesis and the spectral changes of nanoparticles. It has been found that many gadolinium compounds doped with Eu^3＋ have a higher luminous efficient due to high efficient energy transfer from Gd^3＋ to Eu^3＋ ions, moreover, PO4^3＋ groups show high absorption in VUV region, thereby, GdPO4： Eu^3＋ could be applied to plasma display panels. Nanocrystalline GdPO4： Eu^3＋ was prepared by co-precipitation method with EDTA-2Na. The results of XRD indicated that nanocrystalline GdPO4： Eu^3＋ with the monoclinic monazite type was synthesized at 700℃, the XRD intensities of the samples increased with increasing of annealing temperature due to much better crystallization. By applying the Scherrer formula to the full width at half maximum of the （200） diffraction peak, the mean particle sizes could be calculated as 18 nm and 40 nm, for the samples annealed at 700 ℃ and 800 ℃, respectively. The TEM images of the samples show the primary crystal size to be in consistent with the mean particle size obtained from XRD. The excitation spectrum of GdPO4： Eu^3＋ consist of several bands. The bands in the region from 200 nm to 300 nm may be due to the charge transfer band, the other bands from 300 nm to 500 nm are assigned to the absorption band of Gd^3＋and Eu^3＋ ions. The results of emission spectra exhibit all of emission peaks associated with ^5D0→^7F1 transition, the relative intensity order of the emission is I（^5D0→^7F1 ） 〉 I（^5D0→^7F2） 〉 I（^5D0→^7F4）, the emission intensities of the samples are increased with increasing of annealing temperature due to much better crystallization, a little broad emission peaks in smaller nanoparticles are mainly from the lattice distortion. The emission spectra under 315 nm excitation display that energy transfer exist between Gd^3＋ and Eu^3＋ ions effectively.