PbFCl闪烁晶体中十字状缺陷的成因分析

Formation Factor Analysis of Criss-cross-like Defects in PbFCl Scintillation Crystal

坩埚下降法生长的PbFCl晶体中的十字状缺陷对晶体的透光性能有较大影响。用电子背散射衍射测量了十字状缺陷的结晶学方位,并用X射线粉晶衍射、热重-差热分析、扫描电镜以及选区电子衍射对含十字状缺陷和不含十字状缺陷的晶体的结构和成分进行了对比研究。结果表明,十字状缺陷两臂分别平行于[110]和[110]方向,含十字状缺陷的晶体中存在纳米Pb颗粒。据此提出一种十字状缺陷成因的假说,认为PbCl2原料受热分解产生的Pb颗粒在PbFCl晶体中产生应力点,十字状缺陷是应力作用下沿[110]方向和[110]方向形成的微小开裂。

Cross-like defects, found in PbFC1 scintillation crystals grown by Bridgman method, have great influence on the transmittance of the crystal. The crystallographic orientation was tested by EBSD （Electron Backscatter Diffraction ）. The structure and composition of the PbFC1 crystals were characterized by XRD, TG-DSC, SEM and SAED （Selected Area Electron Diffraction）, to compare the difference＂ between the PbFC1 crystals with and without criss-cross-like defects. The results indicate that the two arms of the cross-like defects were [ 110] and [ 11-0] directions, and the Pb nano-particles were observed in PbFC1 crystal with cross-like defects. It is proposed that the PbC12 raw materials were broken down into Pb nano-particles when they were heated, which created the inner stress points. A hypothesis that the cross-like defects are micro-cracks paralleling [ 110] and [ 11-0] directions formed by the inner stress was proposed.