Analysis on crystal cracking of PWO

The PWO crystal was grown by Cz method. We found the cause of crystal cracking was as follows: lateral crack; longitudinal length crack; along the cleaveage place crack; random fracture. Structure analysis shows that structure stress which cause the random fracture can be decreased through select high pure raw material and perfect sub-crystal, and main factor of crystal cracking is caused by thermal stress. Through a lot of experiments we have known that crystal cracking of thermal stress included not only along cleavage place crack but also lateral stratum crack and longitudinal length crack which was caused by dissimilar coefficient of expansion in all directions. During designing stable temperature field and selecting rational technology parameters and annealing process, perfect crystal was grown.