Magnetic and pinning force studies of powder-melt-processed YBCO superconductor

The magnetic and electrical properties of powder-melt-processed (PMP) YBa2Cu3Oδ (YBCO) are discussed. The magnetic critical current densities, Jc, at 77 K, 1 T, for two samples of YBCO, processed at different temperatures, were 1.43x104 and 1.46x104 A/cm2. In zero field the magnetic Jcs of the same two samples were 6.27x104 and 5.62x104 A/cm2, respectively, (their Jcs crossing over with variation of field and temperature). The difference between the pinning characteristics of the two samples was examined in terms of the field dependence of the bulk pinning force at 85 K. The DC transport Jcs at 77 K were 2.06x104 A/cm2 in field of 1 T and 1.56x104 A/cm2 at 4 T. The pulse-measured transport Jcs were higher than this. The melt-textured microstructure is claimed to be responsible for the observed Jc,trans.>Jc,mag.. Magnetization relaxation at 1 T as function of temperature, and remanent magnetization relaxation at 77 K after excursions to fields to up to 1 T, were measured, and the results interpreted in terms of the corresponding variations of effective pinning potentials, Ueff.. In the latter case it was determined that Ueff.,77K,1T=0.34±0.01 eV