High oxygen pressure generation of flux-pinning centers in melt-textured YBa2Cu3O7

A strong enhancement of the critical current density, J(c)(ab)(H,T), has be en generated in melt-textured YBa2Cu3O7/Y2BaCuO5 composites by means of hig h oxygen pressure (approximate to 100 bar, similar to 400 degrees C). Enhan cement factors as high as 180% have been found at low temperatures leading high sample performances at 77 K (J(c)(ab) approximate to 1.2 x 10(5) A/cm( 2) at null field). Transmission electron microscopy studies show a high con centration of dendritic-like stacking faults generated as a consequence of the strong nonequilibrium conditions of the transformation from YBa2Cu3O7 t o YBa2Cu4O8. The high concentration of 1/6 < 031 > partial dislocations wit hin the (001) planes are proposed as point-defect pinning centers enhancing J(c)(ab)(H,T) for the H parallel to c configuration. (C) 1999 American Ins titute of Physics. [S0003-6951(99)04939-6].