Preparation of Lanthanum Ferrite Substituted with Mg and Ca

Abstract

Pervoskite lanthanum ferrite and related compounds have attracted considerably due to their wide applications in fuel cells, catalysts, sensors, and environmental monitoring systems. In this work, lanthanum ferrite and substituted compounds have been prepared by combustion synthesis process using lanthanum nitrate, ferric nitrate, and urea. The parent compound has been substituted with alkaline earth metals like Mg and Ca. The synthesized compounds are characterized using thermal analysis, X-ray diffraction (XRD), UV-visible, Fourier transform infrared spectroscopy, scanning electron microscopy (SEM). From thermal analysis, it is seen that Mg2+ and Ca2+ ions have pronounced effect on the phase formation process. From XRD spectrum, it is seen that the crystalline lanthanum ferrite possesses an orthorhombic disorder perovskite structure with space group Pbnm with four formula units per unit cell, where La ion is tetragonally coordinated. The UV-visible reflectance spectra of lanthanum ferrite and substituted compounds shows two prominent absorption bands, which are shifted towards the lower wavelength side on substitution. The FTIR spectra of the parent substituted compounds recorded between 400 to 4000 cm−1. The existence of the prominent bands shows the formation of the single-phase crystalline lanthanum ferrite. From the SEM figure, if we compare the morphological features of the electrodes before and after substitution, it could be seen that the surface of the materials are disintegrated on oxygen evolution and weaken the intergrain spots.