Abstract: | The Pb-based 1212 compounds containing phosphorus were already discovered by us in the (Pb,P)Sr2(Y,Ca)Cu2O
z
system. Among the almost-single phase samples, a sample with the nominal composition of (Pb0.75P0.25)Sr2(Y0.4Ca0.6)Cu2O
z
was a superconductor with the highest T
c of 38 K in the system. Recently, we have been investigating on substitution effect of Ba for Sr on superconductivity in the
(Pb0.75P0.25)(Sr2−x
Ba
x
)(Y0.4Ca0.6)Cu2O
z
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 Ba2+ ions certainly occupied the Sr-sites in the sample. However, we obtain such interesting results as that the T
c 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
c was 40 K for x=0.2 and 0.3 at the best. |