Alternative current conduction mechanisms and effect of Ag substitution on conductivity in Na1−xAgxAlP2O7 (x = 0.4, x = 0.6 and x = 0.8) compounds

Abstract

The Na1−xAgxAlP2O7 (x = 0.4, x = 0.6 and x = 0.8) samples were prepared by solid–state reaction technique at high temperature. The structural and electrical transport properties have been investigated. The x-ray powder diffraction patterns at room temperature show that all samples are formed in single phase and crystallize in the monoclinic system with P21/C space group. The electrical technique was measured in the 200 Hz–5 MHz frequency range and 573–673 K temperature intervals. The impedance plot has shown semicircle arcs at different temperatures and in order to explain the impedance results, an electrical equivalent circuit has been proposed. The maximum value of conductivity achieved for this material is 3.47 × 10−6 (Ω cm) −1 for x = 0.4, 3.12 × 10−5 (Ω cm) −1 for x = 0.6 and 1.64 × 10−5 (Ω cm) −1 for x = 0.8. The conductivity increases with increase in Ag substitution. The frequency dependence of alternative current (AC) conductivity is interpreted in terms of Jonscher's law. The AC conductivity is analyzed by different processes, which can be attributed to several models: the non-overlapping small polaron tunneling model (NSPT) for x = 0.4 and x = 0.6, the correlated barrier hopping (CBH) for x = 0.8. The conduction mechanism is studied with the help of Elliot's theory, and the Elliot's parameters are determined.