Investigating the electrical conduction and relaxation phenomena in rare earth erbium doped lead free 0.94Na0.5Bi0.5TiO3-0.06BaTiO3 by impedance spectroscopy

Abstract

Rare earth erbium (Er3+) doped 0.94Na0.5Bi0.5TiO3-0.06BaTiO3 (NBT-6BT) was prepared via a solid state synthesis route as per the nominal formula 0.94Na0.5Bi0.5-xErxTiO3-0.06BaTiO3 (0 ≤ x ≤ 0.05). Detailed impedance spectroscopy studies, invoking complex impedance and modulus formalisms, were carried out in order to investigate the influence of erbium doping on the long range electrical conduction and localized relaxation in the system. Our results suggest that a low concentration (x = 0.005) of rare earth doping significantly reduces the long range ionic conductivity (with respect to the undoped NBT-6BT value) and decreases the local relaxation, making the system electrically homogeneous. At a higher doping concentration (x ≥ 0.01), enhancement in the electrical conductivity occurs and local relaxation increases in the system. Observed trends are rationalized on the basis of a model, which hypothesizes phase segregation at a higher concentration of Er-doping. Such segregation leads to the formation of pure NBT-6BT regions and Er-saturated phase with probable dissimilar polar symmetry compared to that of NBT-6BT. A possible correlation between grain size, electrical conductivity, activation energy of conductivity, and local relaxation is indicated.