Superconductivity in the Pb-based 1222 Cuprate Containing Boron, (Pb0.5B0.5) Sr2(Y1.9−x Ce x Sr0.1)Cu2O z

We previously reported on the discovery of new Pb-based 1222 cuprates containing boron in the (Pb0.5B0.5)Sr2(RE2−x−y Ce x Sr y )Cu2O z (RE = Pr, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb, and Y) systems. However, none of the cuprates was a superconductor, but a semiconductor with the conduction process of a three-dimensional variable range hopping at low temperatures, despite annealing under O2 atmosphere at 100 atm and 400 °C. Recently, we have discovered that some samples showed superconductivity in the (Pb0.5B0.5)Sr2(Y1.9−x Ce x Sr0.1)Cu2O z system. Among them, the sample with x=0.45 shows the highest zero resistivity temperature at about 10 K and it shows a diamagnetic signal starting at abut 16 K with lowering temperature. The superconductivity is considered to originate from the 1222 phase.