Synthesis of new members of Pb-based 1222 superconductors containing sulfur: (Pb0.75S0.25)Sr2(RE1.6Ce0.4)Cu2Oz (RE = Sm, Gd, Dy, and Ho)

We have discovered new members of the Pb-based 1222 layered cuprates containing sulfur of (Pb0.75S0.25)Sr2(RE1.6Ce0.4)Cu2O z with RE = Sm, Gd, Dy, and Ho. All the samples are of almost-single 1222 phase. From the ρ–T and χ–T measurements, they are found to be superconductors after annealing under 125 atm O2 atmosphere at 400 °C. Among them, the sample with RE = Gd is found to show superconductivity at the highest temperature of 30 K.