GRAIN ALIGNMENT IN BULK YBA2CU3OX SUPERCONDUCTOR BY A LOW-TEMPERATUREPHASE-TRANSFORMATION METHOD

A quench and directional phase transformation process has been develop ed to achieve grain alignment in bulk YBa2CU3Ox Superconductors at tem peratures about 100-degrees-C below the peritectic temperature. Isothe rmal phase transformation of quenched precursors at 890-degrees-C for 3 min is found to result in the formation of more than 75% of YBa2CU3O x phase without any formation of Y2BaCuO5. Phase transformation at hig her temperatures leads to rapid formation Of Y2BaCuO5 in addition to Y Ba2CU3Ox. A well-aligned microstructure is achieved by directional pha se transformation of the quenched compacts as a rate of 10 mm/h. The m agnetic field dependence of the critical current density at 77 K of th e directionally phase transformed material compares well with that of melt-textured YBCO and is superior to that of magnetically aligned and sintered YBCO.