Impedance and modulus studies of magnetic ceramic oxide Ba2Co2Fe12O22 (Co2Y) doped with Bi2O3

Polycrystalline samples of a layered magnetic ceramic oxide, Ba2Co2Fe12O22 (Co2Y), doped with Bi2O3 were prepared by the solid state reaction method. The dielectric impedance properties were studied over the range of frequency between 1 Hz-1MHz and in the temperature range of 313-493 K, using the modulus formalism. The impedance plot showed a first semicircle at high frequency which was assigned to the grain intrinsic effect and a second semicircle, at lower frequencies, which corresponds to grain boundary polarization (conduction phenomenon). A complex modulus spectrum was used to understand the mechanism of the electrical transport process, which indicates that a non-exponential type of conductivity relaxation characterizes this material. The values of the activation energy of the compound (calculated both from dc conductivity and the modulus spectrum) are very similar, suggesting that the relaxation process may be attributed to the same type of charge carriers. The dielectric measurements were studied by fitting the electrical modulus with the Havriliak-Negami function, including the conductivity parameters. The study demonstrates that the investigation of dielectric relaxation, conductivity, and loss of the ferrite materials, as a function of temperature, are essential for future microwave absorption applications of this material. (C) 2011 American Institute of Physics. [doi:10.1063/1.3615935]