JOURNAL OF SUPERCONDUCTIVITY AND NOVEL MAGNETISM, cilt.25, ss.1879-1892, 2012 (SCI İndekslerine Giren Dergi)
We report on the synthesis and detailed composition, thermal, micro-structural, ac-dc conductivity performance and dielectric permittivity characterization of triethylene glycol (TREG) stabilized CoFe2O4 nanoparticles synthesized by polyol method. XRD analysis confirmed the inorganic phase as CoFe2O4 with high phase purity. Microstructure analysis with TEM revealed well separated, spherical nanoparticles in the order of 6 nm, which is also confirmed by X-ray line profile fitting. FT-IR analysis confirms that TREG is successfully coated on the surface of nanoparticles. Overall conductivity of nanocomposite is approximately two magnitudes lower than that of TREG with increase in temperature. The ac conductivity showed a temperature dependent behavior at low frequencies and temperature independent behavior at high frequencies which is an indication of ionic conductivity. The dc conductivity of the nanocomposites and pure TREG are found to obey the Arrhenius plot with dc activation energies of 0.258 eV and 0.132 eV, respectively. Analysis of dielectric permittivity functions suggests that ionic and polymer segmental motions are strongly coupled in the nanocomposite. TREG stabilized CoFe2O4 nanoparticles has lower epsilon' and epsilon '' than that of pure TREG due to the doping of cobalt. As the temperature increases, the frequency at which (epsilon '') reaches a maximum shifted towards higher frequencies. On the other hand, the activation energy of TREG for relaxation process was found to be 0.952 eV which indicates the predominance of electronic conduction due to the chemical nature of TREG. Contrarily, no maximum peak of tan delta was observed for the nanocomposite due to the being out of temperature and frequency range applied in the study.