Crystal Defects of CdWO4 Scintillation Crystals Grown by Bridgman Method

Large size CdWO4 single crystals had been grown by Bridgman method. The typical crystal defects in the grown crystals,such as crystal cracking,silk-like inclusions and crystal darkening,were investigated by optical microscope and electron probe microscopic analysis. CdWO4 single crystals show an evident cleavability nature. The crystal cracking often occurs along the cleavage plane ( 010) due to the thermal stress inside the crystals. There are silk-like inclusions distribute along the axis in the lower part of the crystals as they grow from the feed material containing excess CdO. The silk-like inclusions have been verified to be the CdO deposits from the melts by EPMA analysis. The single crystal would be darkened in color as it is annealed in nitrogen atmosphere at high temperature.