The conductivity of crystals of β-phase material was studied using X-ray techniques. Spike-like diffuse scattering was observed along the [111]-type directions around the Bragg reflections. The activation energy for the conduction process was equal to 0.40eV for a sample which was quenched from 970K, and was equal to 0.54eV for a sample which was quenched from 720K. It was found that the higher the quenching temperature, the higher was the conductivity and the lower was the activation energy. The dependence of the conductivity upon the cooling process was more marked in monocrystalline than in polycrystalline samples. The contribution of the various cooling processes to the conductivity was explained in terms of the degree of ordering of the mobile F ions.

Y.Ito, K.Koto, S.Yoshikado, T.Ohachi: Solid State Ionics, 1985, 15[3], 253-8