Influence of BiFeTaO₃ addition on the electrical properties of Na_0.4725K_0.4725Li_0.055NbO₃ ceramics system using impedance spectroscopy

Polycrystalline samples of (1 - x)(Na_0.4725K_0.4725Li_0.055NbO₃) - x(BiFe_0.5Ta_0.5O₃) (where x = 0.005 and 0.007 were prepared by using a solid state reaction technique. The XRD patterns of the samples at room temperature shows perovskite phase with monoclinic structure. The dielectric constant for x = 0.007 is maximum. Detailed studies of dielectric and impedance properties of the materials in a wide range of frequency (100 Hz-1 MHz) and temperatures (RT-500 °C) shows that dielectric properties were strongly temperature and frequency dependent. Dielectric and electrical properties of samples, indicate that the Curie temperature shifted to higher temperature side with the increase in frequency. The AC conductivity also increases with increase in frequency. The low value of activation energy obtained for the ceramic samples could be attributed to the influence of electronic contribution to the conductivity. The plots of Z″ and M″ vs frequency at various temperatures shows peaks in the higher temperature range (>320 °C). The compounds show dielectric relaxation, which is found to be of non-Debye type and the relaxation frequency shifted to higher side with increase in temperature. The Nyquist plot and conductivity studies showed the NTCR character of samples.