Microstructure and superconductivity in YBa2Cu3O7-x ceramics deformed at high temperatures: II. Magnetic and transport data

The effect of the microstructure formed in a sintered YBa2Cu3O7-x ceramics deformed at 875 degrees C on its magnetic and transport properties has been studied. The refinement of the microstructure was found to eliminate weak links at grain boundaries and to weaken the dependence of the transport critical current on magnetic field, Jct(H). In the deformed ceramics the initial magnetization curve is non-linear for all fields exceeding the first critical field for weak links at grain boundaries, Hc1gb. Owing to the density of intragrain dislocations being increased by two to three orders of magnitude, the intragrain critical current density Jcm(G) is increased by a factor of ten. For instance, at a field of 1 T at 77 K the value of Jcm(G) measured according to the Bean model is 5*103 and 6*104 A cm-2 for the initial and deformed ceramics, respectively.