Studies on polycrystalline layered ceramic oxide: LiFeVO_4

摘要

A new polycrystalline layered ceramic oxide, LiFeVO_4, 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 A, b=13.1119 A and c=16.3426 A. 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 deg C, grain boundary effects at the temperatures > = 125 deg C, negative temperature coefficient of resistance (NTCR) effect and evidence of temperature dependent electrical relaxation phenomena in the sample. The dc conductivity sigma_(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 sigma_(dc), evaluated from complex impedance spectrum, shows a jump of nearly two orders of magnitude at higher temperature (-1.24 x 10~(-5) S cm~(-1) at 350 deg C) when compared with that of sigma_(dc) (1.14x 10~(-6) S cm~(-1) at 50 deg C). Alternating current conductivity spectrum obeys Jonscher's universal power law. The results of sigma_(ac) v. temperature are also discussed.