CHARACTERIZATION OF THE HIGH-TC SUPERCONDUCTOR Y-BA-CU OXIDE - CRITICAL CURRENT AND CRYSTAL-STRUCTURE

Critical currents are measured in the title material. At 9. 5 K, where an apparent resistance is zero, the critical-current density J//c is found to be about 1. 7 A/cm**2 in a sintered sample. For currents smaller than J//c the sample resistivity is less than 2. 3 mu OMEGA multiplied by (times) cm. By X-ray diffraction the crystal structure is found to be essentially of a perovskite type. Its unit cell composed of eight units of the perovskite structure has a face-centered tetragonal symmetry with the lattice parameters a equals b equals 7. 83 plus or minus 0. 02 A and c equals 7. 72 plus or minus 0. 03 A.