Lowered T-c of YBa2(Cu, Zn)(3)O7-delta by homogenizing procedure and annealing treatments

The effects of the homogenizing procedure and annealing treatment on superc onducting transition temperature, T,, were investigated for Zn-substituted YBa2Cu3O7-delta. Samples of YBa2Cu3-xZnxO7-delta (x = 0.00, 0.02, 0.05 and 0.10) were prepared under different conditions. It was found that additiona l pulverization and re-sintering lower T, in Zn-substituted samples. Moreov er, annealing in reduced atmosphere prior to the final oxygenation further decreases T,, resulting in the lowest value (T-c = 46 K for x = 0.10) among T-c's ever reported for Zn-substituted YBa2Cu3O7-delta. This suggests that Zn at the Cu-O chain site moves to the CuO2 plane by annealing samples in reduced atmosphere. Comparison of T-c-suppression effects by Zn and Ni is a lso discussed. (C) 2001 Elsevier Science B.V. All rights reserved.