ROOM-TEMPERATURE CHEMICAL OXIDATION OF DELAFOSSITE-TYPE OXIDES

Examination of the delafossite-type structure of CuLaO2 and CuYO2 suggests that there is room enough to accomodate intercalated oxide ions and the charge compensation resulting simply from the oxidation of an equivalent amount of Cu+ into Cu2+. Reaction with hypohalites in an aqueous solution leads to color change. Evidence of the formation of Cu2+ is given by TGA, iodometric titration, and magnetic (static and EPR) measurements. The obtained La and Y compounds seem to behave in a different way: whereas CuLaO2+x appears as a single phase, CuYO2+x corresponds to a two-phase mixture, with respectively low and high x values, the latter being isostructural with the thermally oxidized compound recently reported by Cava et al. Comparison is stressed between the oxides obtained by oxidation at room and those obtained at higher temperatures. (C) 1994 Academic Press, Inc.