This superionic material was prepared by precipitation from aqueous solution and was characterized by using X-ray diffraction, differential thermal analysis and 19F nuclear magnetic resonance techniques. The temperature and frequency dependences of the conductivity, the modulus and dielectric properties were investigated by means of impedance spectroscopy. An Arrhenius plot of the direct-current conductivity revealed a gradual slope change, at about 355K, from a high activation-energy (30kJ/mol) region to a low activation-energy region (22kJ/mol). At lower temperatures, the real part of the alternating-current conductivity exhibited the usual power-law behavior. However, at high temperatures, a low-frequency dispersion of the conductivity was observed due to space charge polarization which resulted from the high ionic conductivity. An extremely high dielectric constant was measured, with decreasing frequency, due to the space charge polarization. A dielectric anomaly was also observed around the phase transition temperature. A modulus formalism was used to estimate the conductivity relaxation times and these were compared with those deduced from the line-width transition of the 19F nuclear magnetic resonance.

Fluoride Ion Diffusion of Superionic PbSnF4 Studied by Nuclear Magnetic Resonance and Impedance Spectroscopy. M.M.Ahmad, K.Yamada, T.Okuda: Journal of Physics - Condensed Matter, 2002, 14[30], 7233-44