LaBr3:Ce晶体中包裹体的性质及成因探究

Study on the Property and Origin of Inclusions in LaBr3:Ce Crystals

LaBr3:Ce单晶拥有优良的闪烁性能,但是,一些微缺陷(例如包裹体)经常出现在晶体中,这种包裹体对晶体的闪烁性能有一定的不利影响。通过Bridgman垂直下降法生长得到LaBr3:Ce晶体,发现包裹体主要出现在晶体生长的尾部,偏光显微镜下显示存在两种包裹体,一是气孔,二是固体颗粒。X射线衍射、差热分析和拉曼光谱分别测试了含有包裹体和不含包裹体的晶体样品,然而没有发现不同于LaBr3:Ce基体的成分。因此,推测包裹体是结构和组分与基体几乎完全相同的物质组成,根据测试结果,包裹体的形成可以用组分过冷理论来解释。

LaBr3:Ce single crystal has excellent scintillation property,however,some micro-defects,such as inclusions,often appear in the crystal. The inclusions are harmful for the scintillation property of crystals. In this study,the LaBr3:Ce crystals were grown with vertical Bridgman method. It was found that the inclusions mainly appear at the tail end of the crystal ingot.Polarization microscopy shows that there are two kinds of inclusions,one is bubble,and the other is solid inclusion. X-ray diffraction,differential thermal analysis and Raman spectroscopy were used to measure the samples with inclusion and without inclusions. However,no difference could be identified among the two types of samples. Therefore,it is conjectured that the solid inclusions are composed of substances which are similar to the matrix in composition and crystal structure. Based on these measurement results,the formation mechanism of the inclusions is explained with the constitutional supercooling theory.