DIRECT OBSERVATION OF TEXTURED YBA2CU3O7-DELTA CRYSTAL-GROWTH FROM THE MELT

The behavior and kinetics of textured growth of the YBa2Cu3O7-delta(123) compound from Y2BaCuOs (211 )+liquid have been investigated by hot-stage optical microscopy and high-temperature x-ray diffraction methods. The formation of the 123 is found to begin in the liquid of the peritectic melt, not nucleated from 211 crystals as is widely assumed. The quantity of the liquid phase strongly influences the crystal growth and final morphology of the 123. Dynamic studies show that the optimum temperature for 00l orientation of 123 is 940-degrees-C on an MgO substrate. The growth rate of 123 from the melt is rapid; the rate constant was determined to be 0.526X10(-2)s-1.