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

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 1123 K 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 1123 K in air for 2 h. The thermal transformation of the precursor from ambient temperature to 1150 K 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.