COPPER OXYCARBONATES WITH A LAYERED STRUCTURE, NEW PROMISING HIGH T(C) SUPERCONDUCTORS

The ability of CO3 groups to accomodate the perovskite framework opens the route to the possible synthesis of new copper oxycarbonates with a layered structure, which must be considered as promising high Tc sup erconductors. A review of the crystal chemistry of these recently synt hesized new materials is given here. The best performance has been rea ched for die oxycarbonate Tl0.5Pb0.5Sr4Cu2CO3O7 which exhibits a Tc up to 70 K and a Meissner volume fraction of 70 % at 4.2 K.