NEW 02(N-1)N HOMOLOGOUS SERIES CONSISTING OF SUPERCONDUCTING COPPER OXYHALIDE OF THE SR-CA-CU-O-CL SYSTEM

A copper oxyhalide of the Sr-Ca-Cu-O-Cl system has been synthesized us ing a high-pressure synthesis technique. X-ray and electron-diffractio n analyses and high-resolution transmission electron microscopic obser vation have revealed the formation of a homologous series, 02(n - 1)n, in this system. Depending on the synthesis condition, the sample cont aining the same phase can be superconducting or non-superconducting. T he structural models for the members of this series are proposed. X-ra y Rietveld refinement is performed for a nearly single-phase sample of (Sr,Ca)(3)Cu2O4+xCl2-y which shows superconductivity above 80 K. In t hese samples, it is considered that holes are introduced by the substi tution of O2- for Cl- which are located at the apical site of pyramids with CuO2 basal plane.