New class of high T_c structures: Intergrowth of multiple copper oxide perovskite-like layers with double sheets of BiO

Abstract

The structures of two new BiCuO superconductors are determined from their X-ray powder diffraction patterns. Both materials are members of a new structural type: intergrowths of two BiO sheets with n (n=1,2,3...) copper oxide perovskite-like layers. The n=1 compound has a single La2CuO4-like layer, a composition (BiO)2Sr2CuO4 and Tc=6K. The n=2 compounds has layers containing two CuO2 sheets, similar to La2CaCu2O6. It has a range of compositions near (BiO)2Sr2-xCa1+xCu2O6, with Tc near 75IK.It is speculated that the phase with Tc near 120K corresponds to another compound in this new series with n > 2. © 1988.