COMPARATIVE STUDY OF THERMAL, STRUCTURAL,

Abstract

Mg substituted lithium nickel phosphates, LiNi0.925Mg0.075PO4 and LiNi0.9Mg0.1PO4 cathode materials are synthesized by three steps solid state reaction method. These materials are characterized by thermogravimetric analysis (TGA), differential thermogravimetric analysis (DTA), x-ray powder diffraction (XRD), energy dispersive spectroscopy (EDS), Fourier transform infrared (FT-IR) spectroscopy and complex impedance spectroscopy (CIS) techniques. From TGA/DTA study, compound formation temperatures as well as the weight loss regions are identified. XRD studies of the prepared samples confirm the formation of good crystallization and well-defined diffraction peaks without impurities. The single- phase formations of both samples are also confirmed by EDS analysis. From FT-IR study, different peaks are observed at different wavelength regions, which are responsible for the formation of LiNi0.925Mg0.075PO4 and LiNi0.9Mg0.1PO4 compounds. From the impedance analysis, it is found that the dielectric constant decreases sharply at low frequency as compared to that at high frequency and become almost constant on further increasing the frequency for both samples. The dc conductivity values of LiNi0.925Mg0.075PO4 and LiNi0.9Mg0.1PO4 are 3.8 x 10-9 Scm-1 and 3.94 x 10-9 Scm-1 , respectively. The obtained conductivity results are found in the range of the electrical conductivity of semiconductor (10-7 to 103 S/cm), indicating the semiconductor behavior of the samples.