title: Dielectric Relaxation of NiFe2O4/Gd2O3 Core-Shell Nanoparticles.
abstract: Gd2O3 encapsulated NiFe2O4 core-shell nano-particles (CSNPs) have been synthesized by chemical route. The phase formation of the materials is confirmed by X-ray diffraction analysis. The average particle size is found to be 60 nm by transmission electron microscope. The band gap of NiFe2O4/Gd2O3 CSNPs is obtained by UV-visible absorption spectroscopy. The observed band gap of 4.38 eV lies in between the individual band gap of Gd2O3 and NiFe2O4. The frequency-dependent dielectric relaxation of the material is investigated in the temperature range from 303 K to 543 K. The temperature dependent relaxation times are found to obey Arrhenius law having activation energy of 0.3 eV. The Nyquist plots of impedance data are analyzed by the RC equivalent circuit having a constant phase element. The dielectric relaxation is modelled by Havriliak-Negami technique in the electric modulus formalism. The frequency dependent conductivity spectra follow the double power law.
authors.forename: A
authors.initials: A
authors.lastname: Rajesh
authors.forename: Alo
authors.initials: A
authors.lastname: Dutta
authors.forename: K
authors.initials: K
authors.lastname: Gurunathan
authors.forename: T P
authors.initials: TP
authors.lastname: Sinha