Synthesis of delafossite type oxides CuMO₂ (M=Fe, Al, Y, Ga) by the citric-acid based gel technology

Powders of CuMO₂ (M=Fe, Al, Y, Ga) with delafossite structure were synthesized by a gel technology using citric acid (CA) as a complexant. Heating of a mixed solution of CA, H₂O and the constituent metals at 130°C gave a brown transparent gel. The gel was preheated at 350°C to give a powder precursor which was subsequently converted to oxides by heat-treating it at 700°C-1050°C for 12h either in N₂ or in air. X-Ray diffraction and Raman scattering analyses showed that all the samples are virtually of single-phase without any indication of secondary phases. Pure CuMO₂ was successfully synthesized by the CA-based gel technology at lower temperature and with shorter sintering time when compared with those for the conventional solid-state reaction technique.