PbWO_4晶体中的生长层研究

A Study on the Growth Layer in PbWO_4 Crystals

利用光学显微镜和电子探针研究了存在于钨酸铅晶体中的生长层 ,确定这些生长层的成分为固体的铂金颗粒。根据对PbO和WO3原料所做的GDMS分析结果 ,排除了这些铂金颗粒来自原料的可能性 ,而是认为它们来自生长晶体所用的铂金坩埚。并在此基础上提出 ,PbO WO3熔体在高温下对铂金坩埚的熔蚀和溶解为生长层的形成提供了物质基础 ,但由于停电、停降或温度波动而导致固液界面的暂时静止则为熔体中铂金的析出和沉降提供了机会和场所。为抑制生长层的出现 ,建议在生长过程中适当降低液相区的温度或适当缩短晶体的生长周期。

Growth layer existing in PbWO 4 crystals were investigated with optical microscope and electron microprobe and were recognized to be platinum particles.According to GDMS analysis result on the impurities of PbO and WO 3,which were starting materials for growing PbWO 4 crystals,these platinum particles could not come from the raw materials,but from the platinum crucible used for growing crystals.Based on these test results,it was proposed that the etching of PbO WO 3 melt on the platinum crucible at high temperature and dissolving of the platinum in the melt supply materials for the formation of the growth layer.And the temporary motionless (such as power failure or lowering pausing) of solid liquid interface provides an opportunity for the condensing and depositing of the platinum from the melt.It is suggested that decreasing the temperature of liquid zone or increasing the lowering rate of crucible might be effective meaures to minimize the etching of the melt on the platinum and prevent the formation of growth layer.