Thermal diffusion and thermoelectric powers in molten Na-K, Na-Rb, K-Rb and Ag-Au

The electronic contribution to thermal diffusion is calculated using an expression which may be regarded as an extension of the Faber-Ziman theory of the resistivity of molten alloys and the Faber expression for the driving force in electromigration. It was found that the thermal driving force is directly related to the contribution of the ion to the thermoelectric power. To make contact with experiment to Qsup(*e), the electronic contribution to the heat of transport is added, an 'intrinsic' term Qsup(*i) calculated from dense-gas theory. The conclusions, in broad agreement with experiment, are that the electronic contributions are always in opposition: that in Na-Rb, K-Rb and Ag-Au Qsup(*i) outweighs Qsup(*e) and the heavier ion always diffuses to the cold end of the specimen, and that in Na-K the magnitudes of Qsup(*i) and Qsup(*e) are comparable and reversal of the direction of migration can take place as the concentration changes. (author)