CaF2 solid-state electrolytes prepared by vapor pressure exposure and solid synthesis for defect and ionic conductivity tuning

Abstract

CaF2 nano-crystalline materials were synthesized by applying vapor pressure (RH 74 %) treatment and high-energy ball-milling. The resulting fluoride electrolytes were examined by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM) and Nuclear Magnetic Resonance (NMR) studies revealing cubic structure with a crystallite size of 13 nm of particles with a typical size of 65 nm. The ionic conductivity was observed by Electrochemical Impedance Spectroscopy (EIS) which provided a maximum of 4.6·10−6 S·cm−1 at room temperature. Comparing with previous results obtained at higher relative humidity, this parameter can be used for tuning defects and ionic conductivity providing a path to optimize conditions for electrochemical applications.