Improvement of the superconducting transport properties of YBa2Cu3O7-deltaby BaZrO3 doping

We have doped the YBa2Cu3O7-delta,S superconducting ceramics with BaZrO3 up to 75 wt.% and studied the changes of some physical properties. The most i mportant finding is the enhancement of the critical current density, which has a maximum at around 5 wt.% doping level. Compared with the undoped samp les, the critical current density is four times higher if the doping compou nd is introduced prior to the calcination treatment, or two times higher if BaZrO3 is introduced prior to the sintering treatment, The dependence of t he critical current density on the doping level is consistent with the depe ndence of the Seebeck coefficient. We also observed a very small decrease o f the critical temperature. The real density of the samples decreases with increasing doping level as expected from the ratio between the theoretical densities of YBa2Cu3O7-delta and BaZrO3, the effect being important for dop ing levels higher than 25 wt.%.