Thermoelectric Power and Dielectric Studies of Cobalt-Substituted Manganese-Zinc Nanoferrites

Abstract

Cobalt-manganese-zinc nanoferrites with the formula CoxMn0.5−xZn0.5Fe2O4 (x = 0.0, 0.1, 0.3, and 0.5) were prepared by chemical co-precipitation method. The formation of cubic spinel structure particles in nanometer size with no minor phase was confirmed from the XRD patterns of all the samples. The estimated average crystallite size using Scherrer’s formula was found to be in the range of 11–42 nm, in good agreement with TEM result. The measurements of thermoelectric power or Seebeck coefficient were carried out from 100 to 300 °C by the differential method. The results showed a negative value for Seebeck coefficient of samples with x = 0 and 0.1 within the whole measured interval of temperatures. It indicates the n-type semiconductor behavior. However, for the samples with x = 0.3 and 0.5, the sign of Seebeck coefficient is reversed to positive at temperatures 283 and 272 °C, respectively. Also, all the samples were found to exhibit the maximum absolute thermopower value at a certain temperature near to the sample’s Curie temperature. The dielectric properties of samples were studied in the frequency range from 500 Hz to 10 MHz at room temperature. It was found that the dielectric constant (e´) and dielectric loss (tanδ) are influenced by electron hopping mechanism between Fe2+ and Fe3+ ions. The presence of resonance peak in the tanδ curves vs frequency confirms the existence of single relaxation phenomena in the given frequency range for all the samples.