THE NEW FAMILY OF COMPLEX COPPER OXIDES WITH POSSIBLE SUPERCONDUCTING PROPERTIES - PB2SR2R1.33CE0.67CU3O10+DELTA

The new family of complex copper oxides Pb2Sr2R1.33Ce0.67Cu3O10+δ (R=La-Tm) has been prepared. These compounds have two crystal structure types with different values of δ, which depend on the synthesizing conditions (partial oxygen pressure). The crystal structure models for the Sm-containing phases with δ=-0.2 and 1.7 have been determined on the basis of X-ray powder diffraction. The structures of these compounds are closely related to the structure of the known high-Tc oxides Pb2Sr2R0.5Ca0.5Cu3O8+δ but differ from them by the existence of flourite-like (R1.33Ce0.67O2) blocks instead of the (Y0.5Ca0.5□) sheets which divide the (CuO2) sheets. All these compounds are semiconductors on the basis of magnetization and resistivity measurements, but Eu-containing samples which were prepared in a nitrogen atmosphere exhibited a superconducting transition at 24 K with a relatively small volume of the superconducting phase (<3%). © 1990.