Study of Charge Density and Crystal Structure of co-doped LaCrO3 System

Abstract

The co-doped lanthanum chromite system of (La0.8Ca0.2) (Cr0.81Co0.1Cu0.09)O3 sample has been prepared by high temperature solid state reaction technique. The synthesized sample has been characterized for structural, optical, morphological and magnetic properties by powder XRD, UV-vis, SEM/EDS and VSM. Structural analysis revealed that the prepared sample has orthorhombic structure with space group of Pnma. The bonding between the atoms has been analyzed using maximum entropy method (MEM). The bond lengths and mid bond electron densities have been estimated from the 1D electron density profiles. From the optical absorption spectra, the energy band gap of the sample has been calculated as 2.035 eV. From the SEM image, the average particle size of the synthesized sample is 235nm. EDS spectrum of the synthesized sample confirms its purity. Room temperature M-H curves obtained from VSM measurements exhibit predominant antiferromagnetic ordering of the prepared sample. The co-doped LaCrO3 compounds have been primarily used as cathode as well as inter-connector coating materials in solid oxide fuel cells (SOFC). Introduction. Lanthanum chromite (LaCrO3), a perovskite rare-earth oxide material has been investigated for the past five decades due to their rich and interesting properties and essential technological applications. Since lanthanum chromite has high melting point of 2490 °C with high electronic conductivity, it is often used as electrodes in magneto hydrodynamic (MHD) generators [1] and has also been found for use as oxidation catalyst for soot combustion [2], electric heaters [3] and NOx sensors [4]. Lanthanum chromite is a p-type semiconducting material which exhibits properties like, good physical and chemical stability during the oxidation and reduction process, electro catalytic activity, high thermal expansion coefficient and high mechanical strength [5, 6]. Since the transition metal doped lanthanum chromite has the property of mixed ionic and electronic conductivity, they have been used for electrodes and interconnector materials in solid oxide fuel cell (SOFC) which is a solid electro chemical device, converts chemical energy into electrical energy [7]. Usually, LaCrO3 crystallizes in orthorhombic structure with Pnma space group. The transport properties of lanthanum chromites can be studied by the localized behaviour of the d-electrons [8]. Literature showed various preparation techniques to synthesis lanthanum chromites which include sol-gel method, hydrothermal processing, microwave combustion synthesis, pechini method etc. In the present work, (Co, Cu) doped La-Ca based chromites were prepared through solid state reaction method and we report on structural, optical, morphological and magnetic properties of the synthesized co-doped system.