IONIC-CONDUCTIVITY, PARTIAL THERMOPOWERS, HEATS OF TRANSPORT AND THE SORET EFFECT OF ALPHA-AG2-SE - AN EXPERIMENTAL-STUDY(DELTA)

The ionic and electronic partial thermopowers, the partial entropy of silver metal and the Soret effect in alpha-Ag2+deltaSe (low temperatur e phase) have been studied as functions of temperature and deviation d elta from stoichiometry by means of a nonisothermal galvanic cell. The partial ionic conductivity has been measured to complete the informat ion on the defect structure and properties. From a combination of the experimental data, the heat of transport Q(Ag) of silver metal is det ermined. In an additional experiment, Q(Ag), is determined directly f rom a time-resolved measurement of the ionic thermopower. The measured non-isothermal transport properties are discussed in respect to the d efect structure and isothermal transport properties of alpha-Ag2+delta Se. We observe a strong composition dependence of the heat of transpor t Q(Ag) which is explained by a formal analysis on the basis of linea r irreversible thermodynamics. Information on the individual heats of transport of the mobile point defects is extracted.