Synthesis and properties of spinel-type Co-Cu-Mg-Zn-Cr mixed oxides

Different mixed oxides containing Cu, Zn, Co, Mg, and Cr were obtained by c alcining hydroxycarbonate precursors at different temperatures (653 or 873 K). Characterization was performed by X-ray diffraction, thermal analysis, infrared and reflectance spectroscopy, and BET surface area determination. Depending on metal composition the mixed oxides were constituted by CuO, Zn O, CuCrO, ZnCr2O4, CoCr2O4, and CoxCu1-xCr2O4, MgxCu1-xCr2O4, Co2+Cox3+Cr2- xO4 solid solutions. The phase evolution during reduction of the mixed oxid es, followed by in situ X-ray diffraction up to 973 K, showed that the redu cible species, when present, were CuO, CuCrO4, tetragonal CoxCu1-xCr2O4 and MgxCu1-xCr2O4 spinels, with metallic copper and cubic spinels as final pro ducts of reduction. (C) 2000 Academic Press.