Ferritization of copper ions in the Cu–Fe–O system

Ferrite ceramics were prepared utilizing solid state reactions between CuO and Fe3O4 or α-Fe2O3. The samples were analyzed with X-ray diffraction, 57Fe Mössbauer and FT-IR spectroscopies. For the solid state reaction between CuO and Fe3O4, the initial atomic ratios of Cu:Fe varied between 1:299 and 1:2. With an increase in the amount of CuO in the initial reaction mixture, there was a corresponding increase in cuprospinel (cubic CuFe2O4) in the final products of the synthesis. For the initial molar ratio of Cu:Fe=1:2, cuprospinel phase (0.85) and CuFeO2 phase (0.15) were found by XRD, as the result of solid state reaction between CuO and Fe3O4. In this sample, a small amount of CuO was also detected. For the solid state reaction between CuO and α-Fe2O3, the initial molar ratio of 1:1 was used. The samples prepared at a maximum temperature of 800°C, contained similar fractions of tetragonal and cubic CuFe2O4 phases, and also minor phases of CuO and α-Fe2O3 as found by XRD. In the samples prepared at between 1000 and 1350°C, the cubic CuFe2O4 phase was found together with small amounts of CuFeO2 and CuO. Mössbauer spectra showed hyperfine field distributions and on the basis of these spectra, calculated parameters, the possible presence of Cu+ and Fe2+ ions in the samples was discussed. For the samples prepared at 1350°C the FT-IR spectrum suggested a significant increase in Fe2+ ions, whereas the Mössbauer spectrum and calculated parameters were similar to those for the compound Cu0.7Fe2.3O4.