Ionic Conductivity of NaCl: SrCl2 Crystals

The ionic conductivity of NaCl crystals highly doped with SrCl₂(${10}^{\text{−5}}{\text{\hspace{0.17em}≤\hspace{0.17em}c\hspace{0.17em}≤\hspace{0.17em}2\hspace{0.17em}×\hspace{0.17em}10}}^{\text{−2}}$ , expressed in molar fraction) has been measured from room temperature to the melting point. In this wide range of concentration a unique value for the migration energy for the cation vacancy has been found: 0.75 ± 0.02 eV. With this value all the parameters for the creation and motion of lattice defects have been determined. Simple association theory could not explain the observed results. The Debye–Hückel approach was used to account for the observed absence of association at high temperature. Quenching experiments from high temperatures were performed on these doped crystals and a saturation limit of 8 × 10⁻⁴ was found for the dilution of dipoles in the matrix. The effect of clustering of these dipoles was followed by quenching from different annealing temperatures.