Gadolinium substitution and sintering temperature dependent electronic properties of Li-Ni ferrite

Gadolinium substituted Li-Ni soft ferrites with the general formula (Li-0.5 Fe-0.5)(0.5) Ni-0.5 Gd-y Fe2-y O-4, (where 0 <= y <= 0.1) were prepared by standard chemical solid reaction technique. The effects of sintering temperature on the microstructure were investigated. The results exhibit the formation of simple cubic spinel phase with variation in lattice parameters that are associated with the substitution of large size Gd3+ ions. The SEM micrographs show that the high content of Gd3+ ions might prevent grain growth while the effects of sintering temperature on grain size are significant. The Seebeck coefficient, which was determined from the thermo emf measurements, was found to be negative. It demonstrates the majority of charge carriers of n-type, suggests that the mechanism of conduction is predominant caused by hopping of electrons. The resistivity was increased with the increase in Gd substitution, while it decreased significantly with increasing sintering temperature. The dielectric loss factor was found to increase with sintering temperature. (C) 2011 Elsevier B.V. All rights reserved.