下降法生长PWO晶体中光散射中心的观察与分析

Observation and Analysis on the Optical Scattering Centres in PbWO 4 Crystals Grown by Modified Bridgman Method

本文根据光学显微镜、扫描电镜、电子探针微区成分分析和晶体退火过程的实时观察，将存在于 Ｐｂ Ｗ Ｏ４ 晶体中的光散射中心分为３ 种类型：气态包裹物、固态包裹物和微空洞。根据电子探针微区成分分析和 Ｘ Ｒ Ｄ 物相测定，认为固态包裹物的组成为 Ｗ Ｏ３ ， Ｐｂ２ Ｗ Ｏ５ 和杂质聚集形成的低共熔点化合物。 Ｗ Ｏ３ 颗粒是原料中局部 Ｗ Ｏ３ 未充分固相反应的残留物； Ｐｂ２ Ｗ Ｏ５ 是 Ｗ Ｏ３ 和局部过量的 Ｐｂ Ｏ 反应形成的。微空洞是晶体中空位聚集在一起形成的二次缺陷，晶体中的光散射朦芯主要由微空洞构成。通过对光散射中心的成因分析，提出了消除此类宏观缺陷的工艺措施。

Based on the observation with optical microscope,SEM,EPM and in situ on the crystal in the process of annealing,light scattering centers in PbWO 4 crystals can be classified into three types:gaseous inclusions,solid inclusions and tiny voids.The results of EPM and XRD analysis indicated that solid inclusions are composed of WO 3,Pb 2WO 5 and eutectic composition result from the aggregation of impurities.WO 3 particles are the remains of uncompleted solid reactions between PbO and WO 3 powders,while Pb 2WO 5 particles are the products of reaction between WO 3 and excess of PbO in the melt.Tiny voids in crystals originate from the assembly of vacancies and mainly result in light scattering veils with this proposed mechanism on the formation of three types of light scattering centers,technological measures are suggested for eliminating these macro defects.