Electrical properties of Cu substituted Co nano ferrite

The samples Co1-xCuxFe2O4 (0.0 ⩽ x ⩽ 0.6) were prepared using the standard ceramic method. The dielectric constant (ε′), dielectric loss (tan δ) and ac conductivity (σ) were measured at room temperature as a function of the frequency. The results of the dielectric properties were explained on the basis of Maxwell-Wagner behaviour. The effect of Cu2+ ion substitution on the ac electrical conductivity and dielectric properties at different frequencies, 0.1-1000 kHz, were studied. The data revealed that ε′ and tan δ increased as the Cu2+ ion increased, due to the increase in the number of vacancies at the iron site. The Cu2+ ions change the conduction from an n- to a p-type. The Seebeck coefficient (dV/dT) mV K-1 gives a positive sign (p-type) for all samples up to ≈500 K, except for x = 0.6, for which it gives a negative sign. This indicates that the conduction is predominantly caused by electrons hopping between Fe3+↔Fe2+. The mobility was calculated and found to increase with an increasing Cu content. (paper)