Co‐Precipitation of Fe−Cu Bimetal Oxalates in an Aqueous Solution and Their Thermally Induced Decomposition

This work focuses on the preparation of bimetal Fe−Cu oxalates by a co‐precipitation reaction in an aqueous solution and subsequently on their thermally induced decomposition. The formation of solid solutions of Fe−Cu oxalates with various Fe/Cu ratios was studied by energy dispersive X‐ray analysis, X‐ray powder diffraction, transmission 57Fe Mössbauer spectroscopy, and scanning electron microscopy. The results suggest that the bimetal Fe−Cu oxalate precipitated in a structure similar to β‐FeC2O4 ⋅ 2H2O. The maximum relative amount of Cu obtained within the bimetal oxalate was approximately 40 %. However, the single bimetal phase composition was obtained only for a limited range of Fe/Cu ratios. The Fe‐rich samples contained also β‐FeC2O4 ⋅ 2H2O, while the Cu‐rich samples were predominantly composed of CuC2O4 ⋅ nH2O and contained much lower amounts of Fe than expected. The thermal decomposition of the prepared oxalate with the nominal Fe/Cu ratio of 65/35 was studied by in‐situ X‐ray powder diffraction in combination with ex‐situ Mössbauer spectroscopy. The mixing of both metals at the molecular level allowed the preparation of copper ferrite particles at a relatively low temperature of 470 °C. We report the preparation of a series of Fe−Cu oxalates with varying Fe/Cu ratio. Various characterization techniques are employed to study the nature of the Fe−Cu samples. The thermal decomposition of the sample with Fe/Cu≈2 is investigated using in‐situ XRD. Products of decomposition are further examined by Mössbauer spectroscopy. The results shown here might be used for an easy preparation of Fe−Cu mixed oxides at relatively low temperatures.