MAGNETICALLY MELT TEXTURED YBA2CU3O7-DELTA - DISAGREEMENT BETWEEN JC DETERMINED BY MAGNETIC AND DIRECT TRANSPORT MEASUREMENTS

Textured YBa2CU3O7-delta (Y - 123) ceramic material has been prepared from a mixture Of Y2BaCuO5, BaCUO2 and CuO, by solidification in a magnetic field of 7 T. The application of the magnetic field during solidification allows one to control the orientation of the crystals within the material. An annealing temperature above 1040-degrees-C is necessary to obtain a well textured ceramic. The composition of the starting material has an influence on the form of the sample: an excess of 25% by weight of Y2BaCuO5 allows the initial form of the sample to be preserved. Electrical transport and magnetization measurements are reported. Transport critical current densities of 7200 A/cm2 in a magnetic field of 2 T and 4300 A/cm2 in 6 T in the case H parallel-to ab planes have been observed at 77 K. A transport critical current density of 1600 A/cm2 in 6 T in the case H parallel-to c-axis has been measured, in spite of the fact that critical currents deduced from magnetic measurements using the Bean model are negligible for fields in excess of 5 T.