Studies on polycrystalline layered ceramic oxide: LiFeVO 4

Abstract

A new polycrystalline layered ceramic oxide, LiFeVO₄, has been prepared by a standard solid state reaction technique. The preparation conditions were optimised using thermogravimmetric analysis (TGA) technique. Material formation under the reported conditions was confirmed by X-ray diffraction studies. A preliminary structural analysis indicated that the crystal structure was orthorhombic with lattice parameters: a=4·3368 Å, b=13·1119 Å and c=16·3426 Å. The phase morphology and surface property were studied by scanning electron microscopy. Complex impedance analysis of the sample indicated bulk contribution to electrical properties at T≤125°C, grain boundary effects at the temperatures ≥125°C, negative temperature coefficient of resistance (NTCR) effect and evidence of temperature dependent electrical relaxation phenomena in the sample. The dc conductivity σ_dc shows typical Arrhenius behaviour when observed as a function of temperature. The activation energy value was estimated to be 0·24 eV. The value of σ_dc, evaluated from complex impedance spectrum, shows a jump of nearly two orders of magnitude at higher temperature (∼1·24 × 10⁻⁵ S cm⁻¹ at 350°C) when compared with that of σ_dc (1·14 × 10⁻⁶ S cm⁻¹ at 50°C). Alternating current conductivity spectrum obeys Jonscher's universal power law. The results of σ_ac v. temperature are also discussed.