Electrical properties, conduction mechanism and modulus of diphosphate compounds

Rubidium aluminium diphosphate was synthesized by a conventional solid-state technique and its conduction properties determined by impedance spectroscopy. X-ray diffraction analysis indicated the formation of a single-phase monoclinic structure (space group P2(1)/c). The AC conductivity was determined using impedance spectroscopy over the frequency and temperature ranges of 40 Hz to 7 MHz and 400-700 K, respectively. The real and imaginary parts of the complex impedance were well-fitted to the equivalent circuit model and the frequency dependence of the AC conductivity followed Jonscher's law. The close values of the activation energies obtained from the relaxation time and the grain conductivity (sigma(g)) indicated that transport could be modelled by a hopping mechanism, probably dominated by the movement of Rb+ cations. The correlated barrier hopping model was used to describe the dominant conduction mechanism. A single relaxation peak was observed in the imaginary part of the modulus suggesting the grain response of the system.