Ac conductivity, electric modulus analysis, dielectric behavior and Bond Valence Sum analysis of Na3Nb4As3O19 compound

The Na3Nb4As3O19 compound is synthesized by solid state reaction method and characterized by X-ray diffraction. The structure is described as a three-dimensional anionic framework having two kinds of tunnels where sodium cations are located. The framework of the title compound is thus of open character and the motion of sodium cations through the tunnels seems to be feasible. This factor led us to study the ionic conduction. In this work, we present the dielectric and electrical properties of Na3Nb4As3O19 compound by using the complex impedance spectroscopy technique, in the frequency range 0.01 – 13000 kHz. The conductivity measurements of the obtained ceramic are studied over a temperature range from 300 to 620 °C. The real and imaginary parts of the dielectric constant were found to decrease with frequency and to increase with temperature. The values of the frequency of the maximum of the imaginary part of the modulus and of the impedance are different indicating a non-Debye type of relaxation process. The values of the activation energy (Ea) calculated by different methods are in conformity. The Bond Valence Sum (BVS) model is used to identify the conduction pathways for the monovalent cations, allowing a better correlation between the electrical and the structural data. It suggests that the most probable sodium conduction pathway is along c-direction.

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