Synthesis and properties of a series of layered copper oxide superconductors with a (Pb0.5Cd0.5) rock-salt dopant layer

Abstract A new series of layered copper oxides with the elements lead and cadmium in the rock-salt dopant layer is reported. Materials with the nominal composition (Pb 0.5 Cd 0.5 ) (Sr 1+ x La 1− x CuO 5 form as the (Pb, Cd)-1201 phase when x ≈0 and are superconducting with a maximum T c of 40 K as measured by the onset of diamagnetism. Materials with the nominal composition (Pb 0.5 Cd 0.5 )Sr 2 (Nd 1+ x Ce 1− x ) Cu 2 O 9 form as the (Pb, Cd)-1222 phase when x ≈0.3 but are not superconducting above 5 K when prepared in air. These data and additional measurements on the previously reported (Pb, Cd)-1212 phase demonstrate the improved properties arising from the lead and cadmium mixture in comparison to either lead and zinc or lead and copper mixtures in the rock-salt dopant layer for samples with the same stoichiometry prepared under the same conditions.