Substitution Effect of Ba for Sr on Superconductivity in the (PbP)(SrBa)(YCa)CuO System.

The Pb-based 1212 compounds containing phosphorus were already discovered by us in the (Pb,P)Sr(Y,Ca)CuO system. Among the almost-single phase samples, a sample with the nominal composition of (PbP)Sr(YCa)CuO was a superconductor with the highest T of 38 K in the system. Recently, we have been investigating on substitution effect of Ba for Sr on superconductivity in the (PbP)(SrBa)(YCa)CuO system. As a result, it is found that the almost-single 1212 phase samples are obtained in the composition area of 0.0≤ x≤0.4. In this area, with increase of x, the lattice parameters a, c and the cell volume V are found to be gradually increasing. This finding can be considered to show that larger Ba ions certainly occupied the Sr-sites in the sample. However, we obtain such interesting results as that the T value is not so enhanced by the substitution in comparison with that of the sample of x=0.0, and that the maximum value of T was 40 K for x=0.2 and 0.3 at the best. [ABSTRACT FROM AUTHOR]