Theory of Thermoelectric Power of Ionic Crystals, IV.

The thermoelectric power Q associated with the movement of silver ions in Ag 2 X (X=S, Se, Te) is discussed, where Q is obtainable by measuring the potential difference between silver electrodes in an arrangement as Ag( T 1 )|AgI( T 1 )|Ag 2 X|AgI( T 2 )|Ag( T 2 ). When a temperature gradient is applied, Q , in general, changes with time because of the thermal diffusion of both electrons and silver ions, and then reaches its steady value. An information on the heat of transport of a silver ion is obtained from the comparison between theory and experiment. An explanation on the heat of transport in ionic crystals is given taking into account the variation of vibration frequency of lattice due to the presence of defects. The theory is compared with the experimental data on silver halides and Ag 2 X available at present.