Impedance spectroscopy, electronic structure and X-ray photoelectron spectroscopy studies of Pb(Fe1/2Nb1/2)O3

Abstract

Impedance spectroscopy is used to study the electrical behaviour of lead iron niobate, Pb(Fe1/2Nb1/2)O3 (PFN) in the frequency range from 100 Hz to 1 MHz and in the temperature range from 203 to 363 K. The frequency-dependent electrical data are analyzed by impedance and conductivity formalisms. The complex impedance plane plot shows that the relaxation (conduction) mechanism in PFN is purely a bulk effect arising from the semiconductive grains. The relaxation mechanism of the sample in the framework of electric modulus formalism is modelled by Davidson-Cole equation. The scaling behaviour of imaginary electric modulus suggests that the relaxation describes the same mechanism at various temperatures. We have studied the electronic structure of the PFN using X-ray photoemission spectroscopy (XPS). The density of states (DOS) obtained from the first principles full potential linearized augmented plane wave calculation of PFN shows a direct energy gap ∼0.43 eV. The XPS spectrum is compared with the calculated DOS spectra. It has been observed that the electrical properties of PFN are dominated by the interaction between transition metal and oxygen ions as its valence band consists mainly of the oxygen p-states hybridized with the iron d-states.