Defect interaction and solid electrolyte transition in AgI-based materials

The first-order phase transition that leads to the superionic phase in AgI-based materials is studied by dc-conductivity measurements and a free energy model. By properly adjusting the model parameters, an abrupt change of disordering concentration, Δη̅, is predicted at a transition temperature, Tt. The temperature dependence of the dc-conductivity, σ(T), is well fitted to the η̅(T) equilibrium configuration obtained from the trial free energy function. The reported comparative study was done using an AgI–KI modified sample. The model also predicts a transition temperature, Tc for a continuous phase transition (Δη̅ = 0).