ELECTRICAL-CONDUCTIVITY DUE TO AMMONIUM ION-TRANSPORT IN (NH4)3[MF6] (M-AL, GA, IN) AND (NH4)2K[ALF6] CRYSTALS

The electrical conductivity σ of (NH4)3[AlF6] and (NH4)2K[AlF6] was measured from room temperature to ca. 400 K by an ac complex impedance analysis. The conductivity of each complex obeyed the Arrhenius relation, σT=σ0exp (-Ea RT). The σ value at 320 K and the Ea value are 3.0×10-4 and 29 and 1.0×10-6 S m-1 and 69 kJ mol-1, respectively, in the order given above. 1H and 19F NMR second moment and spin-lattice relaxation time measurements on (NH4)3[AlF6] confirmed that the electrical conduction is attributable to the self-diffusion of NH+4 ions. The results obtained are compared with those of (NH4)3[GaF6] and (NH4)3[InF6] recently reported. The high σ values for these complexes are related to their crystal structures and anionic reorientational motions. © 1990.