铈离子掺杂浓度对氯化镧(LaCl_3:Ce)闪烁晶体发光性能的影响

Influence of Ce doping concentration on the luminescence properties of LaCl_3:Ce scintillation crystals

本文采用垂直Bridgman法,分别生长了未掺杂LaCl3和掺有不同浓度CeCl3的LaCl3闪烁晶体,并对它们的透光性质、发光性质和光衰减特性进行了测试和对比分析.发现未掺杂LaCl3晶体的吸收边位于215 nm附近,本征发射峰为405 nm,衰减时间在1μs以上.该发光属于纯氯化镧晶体的自陷激子发射,但随着CeCl3掺杂浓度的提高,源于自陷激子(STE)的本征发射强度逐渐降低,LaCl3:Ce晶体中的吸收边逐渐红移至300nm,由Ce3+中心所产生的5d→4f发射逐渐增强,其衰减时间加快至～20 ns.这种现象被解释为LaCl3晶格中的自陷激子向Ce3+离子发光中心的能量传递作用所致.

LaC13：Ce is an excellent rare earth halide scintillation crystal discovered in the beginning of this century. Pure LaCI~ crystal and LaC13 crystal doped with several different Ce concentrations were grown by vertical Bridgman method. Their transmission and luminescence as well as decay time were measured and compared with each other. It was found that the cut-off edge, emission wavelength as well as decay time for pure LaC13 crystals are respectively 215 nm, 405 nm and 1 μs. This emission is explained by the self trapped exciton （STE） of LaC13. However, with the increase of Ce concentration in the crystal, the cut-off edge of LaC13：Ce crystal shifts to about 300 nm, and the luminescence is dominated by the emission originating from 5d-4f transition of Ce ions. Meanwhile, the increase of the luminescence intensity of Ce3^＋ ion emission is accompanied with the expense of STE emission, this anti-correlation between the Ce^3＋ and STE luminescence intensity is interpreted by the energy transfer from STE to Ce ions in LaCl3：Ce scintillation crystals.