Critical current density versus normal-state resistivity in granular high-temperature superconductors with different average grain size

摘要

The resistivity, p, and the critical current density at zero applied magnetic field, J_c, of ceramic Y_1Ba_2Cu_3O_(7-#sigma#) samples with different average grain size, a (from 5 to 14 #mu#m), are reported. These results show that at a given temperature J_c depends only on the specific contact resistance of the average grain boundary junction, #rho#□, so that the product J_c#rho#□ is sample independent. The relevance of #rho#□ and not of a on J_c has been further tested on a subset of samples having very different average grain size but similar #rho#□ for which negligible variations of J_c are observed.