Ion dynamics and structure-dependent conductivity scaling properties in polycrystalline LiK1-xRbxSO4

Polycrystalline LiK1-xRbxSO4 mixed crystals (with x=0.1 and 0.2) have been synthesized by air quenching of the melt and characterized by X-ray powder diffraction and DSC measurements. Their ionic conductivity has been measured as a function of temperature over a wide frequency range. From an analysis of the frequency-dependent conductivity at different temperatures below and above the reconstructive phase transition, the dc conductivity, the hopping frequency of mobile ions and the exponent n of the ac dispersive regime are determined. The values of the activation energy for the ac and dc conductivities and that of the hopping process are found to be almost the same, implying that the charge-carriers concentration is independent of temperature. The power-law exponent n of the conductivity spectra has average values of 0.57 and 0.66 in the room- and high-temperature phases, respectively, indicating different conduction properties in the two phases. Moreover, scaling of the conductivity spectra at the room- and high-temperature phases points to the structural influence on the microscopic dynamics of mobile ions.