The temperature dependence of the proton conductivity of MHAO4 and M3H(AO4)2, where M was K, Rb, Cs, or NH4 and A was S or Se, was calculated for low-conductivity phases near to the phase transition temperature. Observed deviations from the Arrhenius law, for the temperature dependence of the conductivity below the transition temperature, were explained in terms of the effect of ferroelectric ordering, of the first-order nature of the phase transition, and of the propagation of protonic defects.

A.Gordon: Physical Review B, 1995, 52[10], R6999-7001