Thermal Diffusion in Crystalline Binary Compounds with Narrow Range of Homogeneity - II. Stationary Thermal Diffusion in β-Ag2+δS

The experimental determination of the (reduced) heat of transport of silver, Q* Ag , in β-Ag 2+δ S by the direct measurement of the silver flux in a given temperature gradient, under the condition of equal composition at the ends of the crystalline sample, is reported. The measurement is based on the application of galvanic cells for the simultaneous control and measurement of both the silver flux and composition. A set of data for the heat of transport of silver is determined for 210°C < T < 270°C and 0.96.10 -3 < δ < 1.7.10 -3 . The measured values for the heat of transport, Q* Ag , are positive and nearly independent of the composition of β-Ag 2+δ S. Thus, a flux of silver metal which is induced by a temperature gradient is directed towards the low temperature side of the crystal. In addition, a strong temperature dependence of Q* Ag was observed.