Oxygen concentration dependence of superconductivity in Pr-substituted Ln1−xPrxBa2Cu3O7−y (Ln = Y, Nd, Gd)

The Pr content x dependence of the superconducting transition temperature Tc is examined for various oxygen concentrations by quenching the samples of the Pr-substituted Ln1−xPrxBa2Cu3O7−y, where Ln is Y, Nd and Gd. In the case of Ln = Y, the initial rate of decrease of Tc by Pr substitution (−dTcdx) decreases with decreasing oxygen concentration for 6.6 < 7 − y < 7.0, then becomes constant for 7 − y < 6.6. In contrast, the effect of Tc-suppression by Pr in the case of Ln = Nd does not depend upon the oxygen concentration, and is much stronger than that in the case of Ln = Y. In the case of Ln = Gd, intermediate behavior between those of Y and Nd is observed, corresponding to the ionic size of Ln.