Effect of synthesis temperature on the magneto-electrochemical properties of LaFe0.9Co0.1O3 nanoparticles

Abstract

Abstract Orthoferrites LaFe 0.9 Co 0.1 O 3 nanoparticles were synthesized by a polymer pyrolysis method and calcined at 700, 800, 900 and 1000 °C for 3 h in air. The structure, morphology, valence states, magnetic and charge-discharge properties of the nanoparticles were characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray absorption near edge structure (XANES), X-ray photoelectron spectroscopy (XPS), vibrating sample magnetometer (VSM) and a potentiostat/galvanostat electrochemical cell system, respectively. Rietveld analysis confirmed the presence of a single phase and that the perovskite lattice exhibited an orthorhombic distortion. The average crystallite sizes increased from 32 ± 6 to 78 ± 6 nm with increasing calcination temperature. From the XANES and XPS results, the valence states of Fe and Co ions in samples were Fe 3+ , Co 3+ and Co 2+ and the ratio of the number of Co 3+ and Co 2+ states varied between samples. All samples exhibited ferromagnetic behavior at room temperature with a maximum magnetization value of 1.0 emu/g for the sample calcined at 900 °C. The relationship between the Co 3+ /Co 2+ ratio and the origin of the ferromagnetism is discussed. The highest discharge capacity of electrodes made from LaFe 0.9 Co 0.1 O 3 nanoparticles was 1150 mAh/g, suggesting the high surface area to volume ratios of the nanoparticles.