Synthesis and Ionic Conductivity of Phosphate-Sulfate Fluorapatites Ca10-xNax(PO4)6-x(SO4)xF2 (x = 0;3;6)

Abstract BackgroundSolid-state electrolytes for Solid Oxide Fuel Cells (SOFC) with high ionic conductivities has attracted great interest for electrochemical applications because of their interesting ionic conduction. MethodsComples impedance spectroscopy (CIS) was used to study the electrical properties of Phosphate-sulfatefluorapatite.FindingsPhosphate-sulfatefluorapatite Ca10-xNax(PO4)6-x(SO4)xF2(x = 0;3;6) ,have been synthesized by the solid-state reaction at high temperature.The samples have been characterized by X-ray Diffraction(XRD), Fourier transform infrared spectroscopy (FTIR), Raman scattering spectroscopy, and Transmission Electron Microscopy (TEM) techniques. XRD study shows that these materials crystallize in the hexagonal system with P63/m as a space group. An impedance analysis has been used to analyze the electrical behavior of the samples at different temperatures. Evidence of temperature-dependent electrical relaxation phenomena is observed. The bulk resistance decreases with increasing temperature, showing a typical negative temperature coefficient of resistance (NTCR).Ac-conductivity measurements have been performed on a wide range of frequencies and temperatures. The ionic conductivity follows the Arrhenius and the Jonscher laws.