Copper-zinc-cobalt-chromium hydroxycarbonates and oxides
- Universita La Sapienza, Rome (Italy)
Hydroxycarbonate precursors with different Cu/Zn/Co/Cr atomic ratios and Cu-Zn-Co-Cr oxides obtained by thermal treatment of the precursors at different temperatures (623, 723, and 973 K in air) have been examined. Characterization has been performed by X-ray powder diffraction, diffuse reflectance spectroscopy, thermal analysis, surface area determination, and measurement of magnetic susceptibility. X-ray diffraction patterns show that the precursors are essentially hydrotalcite-like materials with the general formula (M{sup 2+}){sub 6}(M{sup 3+}){sub 2}(OH){sub 16}CO{sub 3}{center_dot}4H{sub 2}O(M{sup 2+} = Cu, Zn, Co; M{sup 3+} = Cr). Thermal decomposition of the precursors occurs in four steps; the first three (up to T = 623 K) consist of complete dehydration of the sample, and the fourth (623 {le} T {le} 773 K) is due to the release of CO{sub 2}. The precursor structure collapses at T {le} 623 K, giving rise to nearly amorphous materials. Crystalline oxide mixtures are formed only after complete release of CO{sub 2}. X-ray diffraction patterns show that the oxides obtained by calcination of 973 K consist of a mixture of CuO, ZnO, and ZnCr{sub 2}O{sub 4}-ZnCo{sub 2}O{sub 4}-Co{sub 3}O{sub 4} spinel solid solutions. According to reflectance spectroscopy and magnetic susceptibility measurements, the inclusion of Zn{sup 2+} and Co{sup 3+} ions in the spinel-like solid solution seems to be privileged with respect to the formation of separate Co{sub 3}O{sub 4} and ZnO phases.
- OSTI ID:
- 486274
- Journal Information:
- Journal of Solid State Chemistry, Journal Name: Journal of Solid State Chemistry Journal Issue: 2 Vol. 119; ISSN 0022-4596; ISSN JSSCBI
- Country of Publication:
- United States
- Language:
- English
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