Electrical properties of Cu substituted Co nano ferrite

The samples Co 1− x Cu x Fe 2 O 4 (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 Cu 2+ 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 Cu 2+ ion increased, due to the increase in the number of vacancies at the iron site. The Cu 2+ ions change the conduction from an n- to a p-type. The Seebeck coefficient (d V /d T ) 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 Fe 3+ ↔Fe 2+ . The mobility was calculated and found to increase with an increasing Cu content.