SUPERCONDUCTOR WITH TC UP TO 80-K IN THE COMPOUND (LN,CA)(SR,BA)2(C,CU)CU2O7-DELTA

We have synthesized a new family of oxycarbonate compounds (Ln,Ca)(Sr, Ba)2(C,CU)Cu2O7-delta (Ln: rare-earth metals) with a so-called ''CO3-1 212'' structure. Two kinds of single phase in the general formula Er0. 5Ca0.5Sr2-xBaCu3-yCyO7-delta with (x, y) = (0.6, 0.5) and ( 1.3, 0.4) were prepared at different CO2 partial pressures. The former compound shows a superconducting transition at about 45 K, and the latter has T (c) up to 80 K. This rise in T(c) may come from the increase of carrie r density because of the decrease of carbon content. We have also stud ied the Ln-dependence, and it is revealed that most of the compounds L n0.5Ca0.5Sr0.7Ba1.3Cu2.6C0.4O7-delta ShoW the same results, except for Ln = Ce and Th, which did not construct the structure, and also Ln = Pr, which shows suppressed superconductivity with T(c) of 30 K.