Phase evolution of the quenched melt of YBa2Cu3O7-δ with 20 mol% Y2BaCuO5 additions

Samples of YBa2Cu3O7-δ mol% Y2BaCuO5 have been melt processed and quenched from temperatures ranging from 975 to 1100. The microstructure of the samples have been characterized via a combination of x-ray diffractometry, optical microscopy, scanning electron microscopy, 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 deg. C in air. The average yttrium content differs for BC1 and BC2, and it is 4.3 and 5.1 at.%, respectively. Holding times of 20 hours at temperatures above or equal to 1040 deg. C give rise to a dendritic pattern of BC1 surrounded by BC2. The complex changes of the nature of the melt as a function of temperature and time are likely to play a significant role in the mechanism of melt texturing. (author)