DC electrical resistivity study of granularity in YBa2Cu3O7/Ag composites

Temperature-dependent electrical resistivity in a Set of YBa2Cu3O7-x/Ag composites, 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 current frustration caused by misalignment of anisotropic grains and sample defects such as voids and cracks are estimated from the residual resistivity rho(0) and the temperature coefficient of resistivity d rho/dT. Variation of these parameters with Ag vol.% quantifying the extent of granularity indicates that granularity in the composites decreases and their electrical characteristics tend to be identical to that of Ag-free YBa2Cu3O7-x single crystals and epitaxial thin films as Ag vol.% approaches a value where onset of current percolation occurs through Ag channels. The increased alpha and decreased rho(wl) observed at higher Ag vol.% explains the larger grains in the composites with narrow size distribution.