Frequency dependence of ionic conductivity and dielectric relaxation studies in Na 3H(SO 4) 2 single crystal

Abstract

Electrical impedance measurements of Na 3H(SO 4) 2 were performed as a function of both temperature and frequency. The electrical conductivity and dielectric relaxation have been evaluated. The temperature dependence of electrical conductivity reveals that the sample crystals transformed to the fast ionic state in the high temperature phase. The dynamical disordering of hydrogen and sodium atoms and the orientation of SO 4 tetrahedra results in fast ionic conductivity. In addition to the proton conduction, the possibility of a Na + contribution to the conductivity in the high temperature phase is proposed. The frequency dependence of AC conductivity is proportional to ω s . The value of the exponent, s, lies between 0.85 and 0.46 in the room temperature phase, whereas it remains almost constant, 0.6, in the high-temperature phase. The dielectric dispersion is examined using the modulus formalism. An Arrhenius-type behavior is observed when the crystal undergoes the structural phase transition.