Effect of sodium substitution by yttrium on the structural, dielectric and electrical properties of BaNaYNbO ceramics.

The effects of Na substitution by Y on the structural, microstructural, dielectric and electrical properties of BaNaYNbO compositions with (x = 0, 0.02 and 0.04) have been studied in detail. The solid solutions of different compositions were prepared by the solid state reaction route method and characterized by X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), and Complex Impedance Spectroscopy (CIS) techniques. The XRD study confirmed that all prepared compositions have a single-phase orthorhombic tungsten bronze structure with space group 2 at room temperature. The microstructural studies revealed a grain shape and size change in response to increasing Y concentration. The dielectric properties of the obtained compositions are evaluated over a temperature range of 40-600 °C. The dielectric properties were improved for the YO-substituted BaNaNbO compound compared to the undoped BaNaNbO compound. The non-Debye type relaxation mechanism is confirmed by the -Z″ versus Z' traces. The grain contribution was studied using an equivalent electrical circuit with a Resistor R, a Capacitor C, and a Constant-Phase Element CPE in parallel, in the absence of the grain boundary response and the electrode effect in the frequency range 10 Hz-1MHz. The experimental AC conductivity data were evaluated by using Jonscher's power law. The activation energies obtained from the relaxation and conduction processes, present two different regions as a function of temperature related to the two electrical processes for the prepared ceramics.