Effect of ytterbium on the electrical properties of Li-Co ferrite

The real part: of the dielectric constant epsilon ' as well as the ac resistivity of the rare earth ferrite Li0.5+ZYbxCozFe2.5-2z-xO4, 0.0 less than or equal to x less than or equal to 0.2, z = 0.1 were measured at different temperatures (300-800K) as a function of frequency (10 kHz-5 MHz). More than one hump was obtained due to the presence of different polarization processes and conduction mechanisms. The obtained data were discussed on the basis of the valence exchange between (Fe3+, Fe2+), (Fe2+, Yb3+) and (Fe3+, Co2+). The values of the activation energy indicate the semiconducting properties of the investigated samples. Theoretical fitting was carried out for the samples with different Yb concentrations and the reported data were found to be typical. The interaction mechanisms for the samples under investigation have been studied in the temperature range (300-800 K). (C) 2001 Elsevier Science Ltd. AU rights reserved.