Cation substitution to in site in metallic-type conducting oxide, Cu₆O₈InCl (Part 1) - Substitution of group II elements (Ca, Cd)

Metallic-type conducting oxide, Cu₆O₈In_1-xM_xCl (M=Ca and Cd) whose In site is substituted by Ca or Cd was synthesized by decomposition of molten salt. The crystal structure and electric conductivity of these compounds were investigated. All the compounds synthesized are isostructural to the original compound, Cu₆O₈InCl. The limits of substitution were x=0.17 for M=Cd and x=0.20 for Ca. The lattice parameter of Cu₆O₈In_1-xM_xCl (M=Ca and Cd) increased with increasing amount of substitution obeying Vegard's rule. The lattice parameters at the limit of substitution were α=0.918 nm for M=Cd and α=0.919 nm for Ca. Crystallite size decreased from 90 nm at x=0.00 to 45 nm at x=0.20 with increasing x. However, lattice strain was constant in the range of x studied. Electric resistivity increased with increasing of x for all the compounds studied and superconductivity was not observed down to 12 K. It suggests that doping of a hole by substitution of a divalent cation to In³⁺ is not effective in changing the charge of Cu in Cu₆O₈In_1-xM_xCl (M= Ca and Cd), which controlls the conductivity of superconducting copper oxides.