Ionic Conduction in β-Ag2Te and β-Ag2Se

The ionic conductivity, σ i , of β-Ag 2 Te and β-Ag 2 Se is estimated from the time constant of the ionic polarization with the help of the galvanic cell Ag|AgI|specimen|Pt, showing that σ i depends on the composition (deviation from the stoichiometric ratio) in contrast with the composition-independent σ i in their α phase. The chemical potential of Ag ion, ζ i , known from the e.m.f., E , of the cell is also dependent on the composition in the β phase, and accordingly E does not represent the relative position of the Fermi level as in the α phase. This composition dependence of ζ i and σ i is accounted for by a simple theory. In addition, the electronic properties measured as functions of E are also compared with the theory with a correction to E by ζ i .