Formation of LaFeO3 and thermal decomposition reactions in lanthanum(III) oxalate–iron(II) oxalate crystalline mixture

Thermal processes involved during the decomposition course of La2(C2O4)3·10H2O–FeC2O4·2H2O (1:2 mole ratio) mixture up to 750 °C, in an atmosphere of air, were monitored by thermogravimetry and differential thermal analysis. X-ray diffraction and Mössbauer spectroscopy were used to characterize the intermediates and the final product. The results showed that a microcrystalline or possibly amorphous iron(III) oxide with a paramagnetic nature was appeared in the early stages of decomposition at 250 °C. By increasing the temperature, a well crystalline hematite with ferromagnetic properties was obtained. XRD pattern of the mixture calcined at 1100 °C shows the formation of LaFeO3 single phase in consistent with the hyperfine magnetic splitting (one sextet of lines) characteristic of LaFeO3 obtained in the Mössbauer spectra of the mixture calcined at the same temperature.