DC electrical resistivity study of granularity in YBa2Cu3O7/Ag composites

Temperature-dependent electrical resistivity in a Set of YBa2Cu3O7-x/Ag com posites, all prepared under an identical sintering schedule, is analyzed to extract granularity information. The weak-link resistivity rho(wl) across the grain boundaries and the percolation factor alpha arising due to curren t frustration caused by misalignment of anisotropic grains and sample defec ts such as voids and cracks are estimated from the residual resistivity rho (0) and the temperature coefficient of resistivity d rho/dT. Variation of t hese parameters with Ag vol.% quantifying the extent of granularity indicat es that granularity in the composites decreases and their electrical charac teristics tend to be identical to that of Ag-free YBa2Cu3O7-x single crysta ls and epitaxial thin films as Ag vol.% approaches a value where onset of c urrent percolation occurs through Ag channels. The increased alpha and decr eased rho(wl) observed at higher Ag vol.% explains the larger grains in the composites with narrow size distribution.