Influence of thermal annealing on the dielectric properties and electrical relaxation behaviour in nanostructured CoFe2O4 ferrite

Nanocrystalline cobalt ferrite particles with the grain size of 8 nm were synthesized by using the co-precipitation technique and subsequently heat treated to obtain larger grain sizes. The effect of grain size, cation distribution, frequency and temperature on their dielectric properties has been studied. The dielectric constant ( epsilon') of 8 nm grains is found to be an order of magnitude higher and the dielectric loss ( tan delta) is an order of magnitude smaller compared to those of the micron-size particles. The dielectric relaxation is found to be non-Debye in nature with the activation energy decreasing with thermal annealing due to structural perfection.