New layered cuprates CaBa 2R 2Cu 2Ti 2O 12 and (R,Ce) 2Ba 2(R,Ca) 2Cu 2Ti 2O 14 (R = Sm, Gd)

Abstract

New layered cuprates CaBa 2R 2Cu 2Ti 2O 12 and (R,Ce) 2Ba 2(R,Ca) 2Cu 2Ti 2O 14 (R = Sm,Gd) are reported based on the frameworks of CuO 5 square pyramids and TiO 6 octahedra with BaO, Ca or fluorite-type (R,Ce) 2O 2, and rocksalt-type (RO) 2 layers in between. Single phases were obtained for the compositions CaBa 2R 2Cu 2Ti 2O 12 and R 2.0Ce 0.9Ba 2Ca 1.1Cu 2Ti 2O 14 (R = Sm,Gd), respectively. For CaBa 2R 2Cu 2Ti 2O 12, the atom array along the c-axis is Ca(CuO 2)(BaO)(TiO 2)(RO) 2(TiO 2)(BaO)(CuO 2) Ca, where (RO) 2 takes the rocksalt-type configuration. Replacement of Ca by the fluorite-type layer (R,Ce) 2O 2 gives the latter system. X-ray Rietveld refinements for the single phases CaBa 2Sm 2Cu 2Ti 2O 12 and Sm 2.0Ce 0.9Ba 2Ca 1.1Cu 2Ti 2O 14 revealed the partial substitutions of R for Ca in the Ca sites and Ca for R in the R sites. Superconductivity has not been achieved in either system even after cation substitutions or annealing under various conditions.