Enhanced Jc and improved grain-boundary properties in Ag-doped YBa2Cu3O7−δ films

A large increase (∼8×) in critical current density, Jc, was achieved for in situ laser ablated YBa2Cu3O7−δ–Ag films. High-resolution Auger electron spectroscopic investigation indicates that the Ag-doped films are stoichiometric with a relatively low grain-boundary extension (8 nm) in contrast to undoped YBa2Cu3O7−δ films (32 nm). Further analysis suggests that the doped film contains a much lower silver content (<0.15 wt %) than in the target material (5 wt %). These observations are in excellent agreement with the temperature dependence of Jc, the room-temperature resistivity, and the surface resistance results. Thus, Jc enhancement in Ag-doped films can be attributed to their superior properties, viz., improved microstructure characteristics and the reduced resistive grain boundaries.