Doping induced enhancement of the critical currents of grain boundaries in high-Tc superconductors

Appropriate doping of the grains provides a means to optimize the transport properties of grain boundaries in high-T-c superconductors. This is demonstrated for the exemplary case of grain boundaries in bicrystalline Ca- and Go-doped YBa2Cu3O7-delta films. By Ca-doping the critical current density is strongly increased and the normal state resistivity significantly reduced as compared to the values obtained for equivalent junctions in undoped films.