Influence of the temperature and the oxygen partial pressure on the phase formation in the system Cu - Fe - O

Copper iron oxides, Cu1‐xFe2+xO4 (0 ≤ x ≤ 0.5), have been synthesized by thermal oxidation of copper ‐ iron mixtures. In this process, the phase formation and the phase stability were investigated as function of the temperature (800°C – 1200°C) and the oxygen partial pressure (1.013 x 101 – 1.013 x 105 Pa). The phase formation starts with the reaction of the metallic components to simple oxides (Fe3O4, Fe2O3, CuO). From these simple oxides, the formation of complex oxides requires a minimum temperature of 800°C. The synthesis of single phase spinel compounds Cu2+1‐2x Cu1+xFe2+xO4±δ is realized for 0.1 ≤ x ≤ 0.5, using specific temperature – p(O2) – conditions for a given value of x. Remarkably, to achieve our goal, we found that the increase of x implies that of the reaction temperature and/or a decrease of the p(O2) in the reaction gas stream. Besides, a single phase spinel CuFe2O4 does not exist in the temperature / p(O2)‐field investigated. Using the results of XRD ‐ phase analysis, T ‐ p(O2) – x – diagrams were constructed. These diagrams allow the prediction of phase compositions expected for different synthesis conditions. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)