MICROSTRUCTURE AND CRITICAL-CURRENT DENSITY OF THE Y-BA-CU-O SUPERCONDUCTOR PREPARED BY MELT PROCESS

The critical current density (J(c)) value increases along the growth d irection from the top to the bottom of the Y-Ba-Cu-O samples prepared by a melt process with a unidirectional growth technique. The volume f raction of Y2BaCuO5 (211) particle is constant all over the sample, wh ile the average size decreases along the growth direction from the top to the bottom. The dependence of J(c) on the volume fraction and the particle size agrees with the theoretical result. It seems that an inc rease of J(c) along the growth direction from the top to the bottom ca n be attributed to the decrease of the 211 average size. The cause of the inhomogeneity for the 211 particle size is discussed.