Nonisothermal transport properties of alpha-Ag2+delta S: Partial thermopowers of electrons and ions, the Soret effect and heats of transport

The ionic and electronic partial thermopowers and the Soret effect of alpha-Ag2+deltaS (low temperature phase) have been studied as functions of temperature and deviation from stoichiometry delta by means of a nonisothermal galvanic cell. From a combination of these data with results from additional measurements of the partial entropy of silver metal in alpha-Ag2+deltaS, the heat of transport of silver metal is determined. The measured transport properties are discussed in respect to the defect structure and isothermal transport properties of alpha-Ag2+deltaS and information on the individual heats of transport of the mobile point defects is extracted. We observe a strong composition dependence of Q(Ag)* which can be explained within our formal analysis. The electronic properties can be interpreted within the model of a non-degenerate electron gas. The scattering factor of electronic defects in the statistical description of thermopower is equivalent to the electronic heat of transport in the phenomenological description. (C) 1997 Elsevier Science Ltd.