Superconductivity of (Pb0.75W0.25)Sr2(RE0.5Ca0.5)Cu2Oz (RE = Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb, and Y) by Annealing in N2 Gas

We have synthesized the Pb-1212 compounds in the (Pb0.75W0.25)Sr2(RE0.5Ca0.5)Cu2Oz (RE = Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb, and Y) system. Every sample shows an onset of resistivity-drop phenomenon near 80 K and zero resistivity. Moreover, the samples with RE = Y and Yb show diamagnetic signals starting from about 78 K and 76 K by lowering the temperature, respectively. From these experimental results, we can see that these phenomena originate from the superconductivity of the Pb-1212 phase in the present system. The Tc value of about 80 K for the sample with RE = Y in the present system is higher than the already reported values for the superconductors annealed under N2 gas. The important thing is that annealing under N2 atmosphere is essential for making the Pb-1212 samples exhibit superconductivity in the present system.