Synthesis of perovskite LaCoO3 by thermal decomposition of oxalates: Phase evolution and kinetics of the thermal transformation of the precursor

Abstract

LaCoO3 precursor was synthesized by solid-state reaction at low temperatures using La(NO3)3·6H2O, CoSO4·7H2O, and Na2C2O4 as raw materials. LaCoO3 was obtained by calcining a precursor, 0.97/2La2(C2O4)3–CoC2O4·5.3H2O, at 1123K in air. The precursor and its calcined products were characterized by thermogravimetry and differential scanning calorimetry, Fourier transform infrared spectroscopy, X-ray powder diffraction, and scanning electron microscopy. A high-crystallized LaCoO3 with a rhombohedral structure was obtained when the precursor was calcined at 1123K in air for 2h. The thermal transformation of the precursor from ambient temperature to 1150K in air presented six steps. The values of the activation energies associated with the thermal transformation of 0.97/2La2(C2O4)3–CoC2O4·5.3H2O were determined based on the Starink equation.