Thermoelectric power of superionic conductor Ag7I4PO4

The thermoelectric power (θ) of Ag₇I₄PO₄ superionic conductor has been studied for the first time from 4 to 75°C; 80°C being its decomposition temperature. Relation between θ and temperature can be expressed by the equation

$\text{?θ = 0.20}\text{10}{}^3\text{T}\text{?0.255}$

for this solid. Analysis of the data yields 0.20 eV as heat of transport of Ag⁺ ion which is very close to its activation energy 0.21 eV. This supports the prediction of the theory of Rice and Roth based on “free-ion” model. This is also in consonance with earlier theories on heats of transport of ions in ionic solids. Indications have been found to justify the assumption that Ag₇I₄PO₄ has average structure.