Generation of Sr2Ca(n-1)CunOy phases (n = 5-7) by high pressure synthesis

Abstract

We prepared Sr2Ca(n-1)CunOy (n = 3-7) phases using a high-pressure apparatus. In the Sr-Ca-Cu-O system, the n = 5-7 members of a homologous series, Sr2Ca(n-1)CunOy, were prepared as mixed phases for the first time. The c-axis length increases linearly with increasing n; c = 6.46(n-1) + 14.3 Å. Half of this slope gives reasonable value of 3.2 Å as the thickness of a Ca and CuO2 plane. It is likely that a 0(Sr)2(n-1)n phase is formed from a 0(Sr)2(n-2)(n-1) phase to intercalate CaCuO2 into its infinite layer because the number of CuO2 planes increases with increasing sintering temperature and synthetic time. Too high temperature and too long synthesis time result in the formation of the infinite layer phase.