OXYGEN CONCENTRATION-DEPENDENCE OF SUPERCONDUCTIVITY IN PR-SUBSTITUTED LN(1-X)PR(X)BA(2)CU(3)O(7-Y) (LN=Y, ND, GD)

The Pr content x dependence of the superconducting transition temperat ure T-c is examined for various oxygen concentrations by quenching the samples of the Pr-substituted Ln(1-x)Pr(x)Ba(2)Cu(3)O(7-y), where Ln is Y, Nd and Gd. In the case of Ln = Y, the initial rate of decrease o f T-c by Pr substitution (-dT(c)/dx) 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 T-c-suppression by Pr in the case of Ln = Nd does not depend upon the oxygen concentration, and is much str onger than that in the case of Ln = Y. In the case of Ln = Gd, interme diate behavior between those of Y and Nd is observed. corresponding to the ionic size of Ln.