Abstract:
The present study demonstrates the reduction in the dielectric loss at room
temperature from 0.149 to 0.027 in the composite of (NdFeO3)0.1-(-
Ba0.7Sr0.3TiO3)0.9 as compared to the undoped Ba0.7Sr0.3TiO3 and correlates with
the charge compensation due to the ionic substitutions for both A site (NdBa)
and B (FeTi) site generated excess electrons, localized hole states and robust
oxygen vacancies (VO) along with different cationic oxidation states. The VO
mediated F center charge transfer mechanism i.e., bound magnetic polaronic
behaviour and defect complex generated between acceptors and ionized VO
reduce electrical conductivity and loss factor. The presence of weak ferromagnetism in the M-H loop reconfirms the F center exchange mechanism in mixed
phase symmetry. The activation energy calculated from impedance spectroscopy, electrical modulus and electrical conductivity analysis supports the
presence of doubly ionized VO. Further, density functional theory based first
principle calculation manifests that the impurity induced depopulation of
valence band edge electrons into a single spin up channel which distorts TiO6
octahedra with fluctuating bond length and Ti 3d eg orbital splitting observed in
decomposed density of states for accommodating excess electrons. These trapped and accommodated electrons reduce the effective electron concentration
which in turn decreases the electrical conductivity and loss factor.
