Dielectric, ferroelectric and impedance spectroscopic studies in TiO2-doped AgNbO3 ceramic

The paper reports the effect of carrier (hole) doping on the dielectric, ferroelectric and electric transport properties of the AgNbO3 (AN) system. Transition metal oxide TiO2 was selected to dope with the AN system in order to partially incorporate Ti4+ in place of Nb5+ cation. The samples of AgNbO3/(TiO2) were prepared by solid state synthesis route. X-ray diffraction pattern confirmed the formation of phase. The modification brought significant changes in the shape and reduction in the size of the grains. X-ray photoelectron spectroscopy confirmed the presence of Ti4+, Ti3+and Ti2+ state and hence the possible hole doping in the system. Improved dielectric properties and lossy ferroelectric loops were observed in the modified systems and were discussed properly. The relaxation mechanisms were studied and analysed by Complex impedance spectroscopy within frequency domain of 100 Hz-1 MHz and chosen temperature 25 °C-450 °C. Only intrinsic (grain) conduction effect was observed in the parent system. In the conduction mechanism of the modified systems, some extrinsic sources were traced of accompanying the intrinsic sources at higher temperatures. The impurity phases were supposed to be the sources of extrinsic conduction effect. The reduced activation energies were related to the low temperature relaxations (below Curie temperature) in the modified systems. The roles of reduced grain size, drastic fall in resistance were also discussed accordingly.