Electrical transport properties of CoZn ferrite-SiO2 composites prepared by co-precipitation technique

CoZn ferrite-SiO2 composites having general formula (1-x)Co0.5Zn0.5Fe2O4+xSiO(2) with x=0.0-0.8 were prepared by co-precipitation technique. The X-ray diffraction analysis of the composites reveals that they are bi-phase. Room temperature resistivity increases from 10(5) to 10(9) (Omega cm) from x = 0.0-0.8. This drastic increase in resistivity may be attributed to the presence of pores and the segregation of Si at grain boundaries. The Arrhenius plots of these samples show that resistivity decreases as the temperature increases indicating their semi conducting behavior. Arrhenius plots show a change of slope at particular temperature (except for x = 0.8) that may be attributed to their Curie temperature. It is observed that the activation energies are small in Para-region as compared to Ferri-region and is an indication of the hopping conduction mechanism. The variation of thermopower with temperature reveals that these samples are degenerate type semiconductors. The values of activation energies calculated from 109 mu(d) vs. 1000/T are slightly lower than the values of activation energies obtained from Arrhenius plots. This suggests that the conduction phenomenon is due to polaron hopping. (c) 2007 Elsevier B.V. All rights reserved.