Synthesis and characterization of LnMCuFeO_5+δ(Ln=Y, La, Pr; M=Ca, Sr, Ba)

New phases of the title family of compounds have been prepared and the synthesis conditions have been optimized. In spite that iron and copper are located in different crystallographic positions, as deduced from Mössbauer analysis, doping of the copper-oxygen planes induced by partial cationic substitution in the trivalent site does not produce superconductivity. © 1993.