PHASE EVOLUTION OF THE QUENCHED MELT OF YBA2CU3O7-Y WITH 20 MOL-PERCENT Y2BACUO5 ADDITIONS

Samples of YBa2Cu3O7-y + 20 mol% Y2BaCuO5 have been melt processed and quenched from temperatures ranging from 975 to 1100 degrees C. The mi crostructure of the samples have been characterized via a combination of x-ray diffractometry, optical microscopy, scanning electron microsc opy, energy dispersive x-ray spectrometry and wavelength dispersive x- ray spectrometry. BaCuO2 (BC1) and BaCu2O2 (BC2) crystallize from the melt of samples quenched from temperatures between 985 and 1100 degree s C in air. The average yttrium content differs for BC1 and BC2, and i t is 4.3 and 5.1 at.%, respectively. Holding times of 20 hours at temp eratures above or equal to 1040 degrees C give rise to a dendritic pat tern of BC1 surrounded by BC2. The complex changes of the nature of th e melt as a function of temperature and time are likely to play a sign ificant role in the mechanism of melt texturing.