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)3Æ10H2O–FeC2O4Æ 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 Mo¨ ssbauer 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 Mo¨ ssbauer spectra of the mixture calcined at the same temperature.