New Copper Oxychlorides Ca4Ln2Cu3O8Cl4, First Members of the Intergrowth Series (Ca2CuO2Cl2)m(Ln2Ca2Cu2O6Cl2)n(Ln= Gd, Sm)

Abstract

The oxychlorides Ca4Ln2Cu3O8Cl4, withLn= Gd and Sm, intergrowths of the T and T* structures have been synthesized for the first time. The HREM study, coupled with EDS analysis, shows that the actual composition of these phases is significantly different from the ideal composition, due to the presence of complex nonstoichiometry phenomena involving the formation of intergrowth defects corresponding to other members with the general formulation (Ca2CuO2Cl2)m(Ln2Ca2Cu2O6Cl2)n. Moreover, substitutions on the anionic and cationic sites are also evidenced. These results demonstrate the high flexibility of the oxychloride layer structure and suggest the possibility to isolate new members in this structural series.