Improvement in the properties of Ag-doped YBa2Cu3O7-x grain boundary Josephson functions

Ag-doped YBa2Cu3O7-x (YBCO) thin films using 5 to 20 wt% Ag-doped YBCO targ ets have been grown by a de sputtering technique on SrTiO3 bicrystals. Crit ical currents of 4 to 5 x 10(6) A/cm(2) at 77 K were measured in YBCO films doped with 5 wt% Ag which has been found to be higher than the value of I x 106 A/cm(2) measured in undoped samples. The normal resistivity decreases by a doping of 5 wt% Ag and increases for higher Ag concentrations. The cr itical temperature, T-c, of the Ag-YBCO films remained unchanged at 92 K as in the undoped YBCO samples. An IcRn product of 170 mu V at 77 It was foun d in Grain Boundary Josephson junctions (GBJJs) with 5 wt% Ag, compared wit h the value of 100 mu V measured in undoped samples at the same temperature . Current-voltage characteristics were measured in GBJJs, showing Shapiro s teps under microwave radiation and Fraunhofer patterns with an external mag netic field. The improvement in the normal and superconducting properties o f Ag-doped YBCO films has been interpreted using the De Gennes model to est ablish that YBCO containing metallic Ag addition shows a superconductor-nor malmetal-superconductor (S-N-S) behavior, thereby the Ag-doping enhances th e weak link behavior and is, therefore, appropriate for electronic applicat ions.