Structural and electrical characterization of LiFe 1/2Co 1/2VO 4

Abstract

A polycrystalline ceramic oxide, LiFe 1/2Co 1/2VO 4, having layered structure (olivine type) has been prepared using a solid-state reaction technique. The preparation conditions have been optimized using thermogravimmetric analysis (TGA) technique. Material formation under the reported conditions has been confirmed by X-ray diffraction (XRD) studies. A preliminary structural analysis suggests orthorhombic unit cell structure with lattice parameters: a = 4.2576 Å, b = 14.6029 Å, c = 11.9508 Å. The phase morphology and surface properties studied using scanning electron microscopy (SEM) suggests polycrystalline texture with reasonable number of voids. The electrical properties have been studied using a.c. technique of Complex Impedance Spectroscopy (CIS). Complex impedance analysis of the material sample has indicated (i) grain boundary effects at all temperatures ( T) ≥ 26 °C, (ii) negative temperature coefficient of resistance (NTCR) effect like that of a semiconductor and (iii) evidence of temperature dependent electrical relaxation phenomena in the material. The d.c. conductivity ( σ dc) shows typical Arrhenius type behaviour when observed as a function of temperature. The activation energy value has been estimated to be 0.38 eV. The results of σ ac as a function of temperature are also described.