The effect of pressure on the conductivity behavior of the (NH4)3H(SeO4)2 superprotonic crystal

The impedance spectra of (NH4)(3)H(SeO4)(2) in low and high-conductive phases under various thermodynamic conditions were analyzed. The measurements were performed by the ac admittance technique along the trigonal c axis of the crystal, i.e., along the direction perpendicular to the plane in which, in the superionic phases, a dynamically disordered H-bond network was formed. Activation energies and activation volumes were calculated for different phases of the (NH4)(3)H(SeO4)(2) crystal from the baric dependencies of dc conductivity and they were correlated with pressure coefficients of the phase transitions. The experimental results were analyzed within the classical hopping model, in terms of the strong proton-phonon coupling and polaronic effect. Published by AIP Publishing.