Impedance spectroscopy study of (NH4)3H (SeO4)2: Evidence of increase in lattice disorder in the low temperature phases

The ac conductivity behavior of superprotonic (NH4)3H (SeO4)2 in low temperature phases IV and III, at temperatures between 240 K and 350 K, has been studied to evidence the evolution of molecular dynamics and its relation to proton transport mechanism. The conductivity was analyzed in the frequency range of the Jonscher's regime, within the classical hopping model, where the conductivity is calculated for hopping of carriers between sites over potential barriers whose height distribution is related to the random spatial distribution of these sites. The complex electric modulus formalism was used for analysis of electric relaxation in (NH4)3H(SeO4)2.