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

Abstract

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.