SYNTHESIS AND PROPERTIES OF A SERIES OF LAYERED COPPER-OXIDE SUPERCONDUCTORS WITH A (PB0.5CD0.5) ROCK-SALT DOPANT LAYER

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 (Pb0.5Cd0.5) (Sr1+xLa1-x) CuO5 form as the (Pb, Cd)-1201 phase when x almost-equal-to 0 and are superconducting with a maximum T(c) of 40 K as measured by the onset of diamagnetism. Materials with the nominal composition (Pb0.5Cd0.5)Sr2(Nd1+xCe1-x)Cu2O9 form as the (Pb, Cd)-1222 phase when x almost-equal-to 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.