Research Papers in Physics and Astronomy


Date of this Version

June 1968


Published in Journal of Physics and Chemistry of Solids, Vol. 30 (1969), pp. 457-459. Copyright © 1969 Elsevier. Used by permission.


Fuller and Reilly [1], Fuller, Reilly, Marquardt and Wells [2], and Allnatt and Pantelis [3] have recently reported the results of measurements of the intrinsic electrical conductivity σ of RbCl, KCl and NaCl, respectively. All of these results showed an anomalous behavior of the log (σT) vs. T-1 plot at temperatures near the melting points of the various crystals. It is the purpose of this note to discuss the suggestion [4] that the anomaly may be due to a trivacancy mechanism.

The plots of the log (σT) vs. T –1 were found to have too great a positive curvature in the intrinsic region to be described by the usual conductivity equations [5] , even when the corrections for Coulomb interactions [6] were used in the analyses [7]. To explain the 6 per cent deviation between their theoretical and experimental results for NaCl at 794°C Allnatt and Pantelis [3] suggested the presence of cationic Frenkel disorder. In their subsequent least squares analysis the interstitial Na ions were found to carry about 61 per cent of the electrical current in NaCl at 794°C. According to the Nernst-Einstein relation the mobile interstitial Na ions would also make a large contribution to the cation diffusion in NaCl. A large interstitial contribution to Na diffusion in NaCl has never been reported [8]. It therefore seems important to point out the characteristics of trivacancy contributions to conductivity.

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