Optimization of the BaZrO3concentration in YBCO films prepared by pulsed laser deposition

YBCO films were prepared by pulsed laser deposition from nanocrystalline targets doped with different concentrations of BaZrO 3 ranging from c = 0.9 to 9.0 wt%. The critical temperature of the films decreases almost linearly with increasing BaZrO 3 content whereas the critical current density shows a maximum near 3.9 wt%. In comparison with undoped YBCO films the accommodation field B * is considerably enhanced and the critical current density is improved in high fields in the films doped with BaZrO 3 , e.g. for c = 3.9 wt% by factor of 4.5 in a field of 5 T at 5 K. In the doped films the BaZrO 3 particles grow epiaxially with YBCO. Transmission electron microscopy results show that the density of the BaZrO 3 particles increases with increasing doping but the particle size remains practically the same (5–10 nm).