INVESTIGATION OF THE CRYSTAL SHAPE CONTROLLABILITY OF YBA2CU3O7-X SINGLE-CRYSTALS IN THE PULLING METHOD

The influence of the geometrical difference on the crystal growth rate of YBa2CU3O7-x (Y123) single crystals in the modified pulling method was investigated. The growth rate of {001} faces appeared on the botto m of the crystals grown along [001] direction (R(cv)(c)) was about 1.6 -2.0 times higher than that of {100} faces appeared on the bottom of t he crystals grown along [100] direction (R(av)(a)). R(av)(a) is more s ensitive to the change of supersaturation than R(ah)(a) (the crystal g rowth rate of {100} faces appeared on the side of the crystals grown a long [100] direction) for the low crystal pulling rate and for the low supersaturation regime, although these faces are crystallographically the same. These difference is attributed to the increase of the tempe rature at the crystal bottom face during the crystalgrowth. It is supp osed from the experimental results that Y123 single crystals having lo ng and nearly straight body parts with expanding about 25 degrees can be obtained in the [001] direction growth of the modified pulling meth od.