INFLUENCE OF GROWTH CONDITION ON MAGNETIC-FLUX PINNING IN YBA2CU3OX SINGLE-CRYSTALS

Relationships between critical current density (J(c)) and crystalline imperfections in YBa2Cu3Ox (123) single crystals have been investigate d. The crystal specimens are grown under various conditions of the sol id Y2BaCuO5 (211) and the melt phase existing together. Compositional distribution of the constituent metal atoms over the cross-sectional a rea is inspected by using an optical microscope, a SEM-EPMA and a TEM. The data support findings that the crystals are very homogeneous and that an included 211 phase does not exist in the 123 crystals. By decr easing the melt composition in the coexisting region of the solid 211 phase with the melt, however, an increase in the concentration of void s is observed, and J, and the effective pinning energy are considerabl y enhanced, showing an introduction of strong flux pinning centers int o the crystals. (C) 1997 Elsevier Science B.V.