Impedance characterisation of LiFePO4 ceramics

Abstract: Pellets of LiFePO4, synthesised by solid state reaction, were sintered at two temperatures, 650 and 770°C and their electrical properties measured by impedance spectroscopy over the temperature range 75 to 300°C. Various equivalent circuits were tested to model the impedance data and a good fit to the bulk response obtained for a parallel combination of a resistance, R 1, capacitance, C 1, and constant phase element, CPE1. For pellets sintered at 650°C, a second element, R 2–C 2–CPE2, was required, in series, to model an impedance attributed to a constriction resistance associated with the poorly sintered ceramic. At higher temperatures and low frequencies, evidence was obtained for a third impedance component attributed to a depletion layer associated with a Schottky barrier at the sample–electrode interface. [Copyright &y& Elsevier]