Temperature-dependent impedance spectroscopy of monovalent double tungstate oxide

The sodium double tungstate NaCr(WO4)2 compound has been synthesized by the ceramic method and characterized by the X-ray diffraction (XRD) technique. The electrical conductivity and modulus characteristics of the system have been investigated in the temperature and the frequency range 592-670 K and 200 Hz-5 MHz respectively by means of impedance spectroscopy. The ac and dc conductivities were studied to explore the mechanism of conduction. Dielectric data were analyzed using complex electrical modulus M* at various temperatures. The non-overlapping small polaron (NSPT) model can explain the temperature dependence of the frequency exponent. The electrical conduction in sodium double tungstate NaCr(WO4)2 compound is presumably caused by the motion of Na+ in the [010] direction tunnel. Conductivity measurements revealed that this compound is not a good ionic conductor probably because of the occupancy of sodium positions, which hinders the motion of the ions along the (NaO6) ∞ columns.