Effects of Y₂BaCuO₅ on the directional growth of YBa₂Cu₃O_x superconductor

The effects of Y₂BaCuO₅ on the microstructure and superconducting properties of YBa₂Cu₃O_x samples, textured using the directional growth of Y₂BaCuO₅, BaCuO₂ and CuO powder mixtures, were studied. Y₂BaCuO₅ moved downward as the sample passed up through the hot zone, and this downward movement affected the superconducting properties of the directionally grown samples. The critical temperature increased, and the resistance transition width decreased as the excess 211 content in the powder mixture increased up to a value, beyond which the temperature decreased and the width increased. The critical current densities of the directionally grown samples were scattered because of the presence of uncontrollable severe cracks perpendicular to the growth direction. As the hot-zone temperature increased, the critical current density of the directionally grown sample increased up to a maximum value (>6000 A cm^-2) beyond which the critical current density decreased. Compared to data from other studies, the hot-zone temperature required to produce a maximum critical current density was lower.