Dielectric, ferroelectric and impedance spectroscopic study of Ta2O5, Sb2O5, and V2O5-doped AgNbO3 ceramic

In this work, silver niobate (AgNbO3) was doped with X2O5 (where, X = Ta, Sb, and V) and the series of samples were prepared by the solid state route. Phase analysis was carried out by the X-ray diffraction technique and the image of the surface morphology of each sample was taken by the Field emission scanning electron microscopy. Complex impedance spectroscopy was used to distinguish the different microstructure contribution in the conduction mechanism. Relaxation behaviour was observed in the imaginary part of impedance Z″(f) and electric modulus M″(f). The appearance of single semicircle in Cole-Cole of (Z′ vs. Z″) and (M′ vs. M″) confirmed a single relaxation process which was identified due to the intrinsic (grain) effect. The absence of any extrinsic interfacial conduction suggested that charge carriers at grain boundaries and sample surface are not activated properly. Therefore, it was presumed that no effective role by the metallic precipitated silver nano particles in electric properties within the chosen temperature range (25 °C-450 °C) containing major dielectric anomalies. The changes in the dielectric and ferroelectric behaviours were also discussed accordingly.