  Polycrystalline Yb substituted NiZn nanoferrites with the compositions of
Ni0.5Zn0.5YbxFe2-xO4 (x= 0.00, 0.04, 0.08, 0.12, 0.16 and 0.20) have been
synthesized using sol gel auto combustion technique. Single phase cubic spinel
structure has been confirmed by the X ray diffraction (XRD) patterns. Larger
lattice constants of the compositions are found with increasing Yb3+
concentration while the average grain size (52 to 18 nm) has noticeable
decrease as Yb3+ content is increased. The presence of all existing elements as
well as the purity of the samples has also been confirmed from energy
dispersive X ray spectroscopic (EDS) analysis. Frequency dependent dielectric
constant, dielectric loss, dielectric relaxation time, AC and DC resistivity of
the compositions have also been examined at room temperature. The DC
resistivity value is found in the order of 10 to power 10 (omega-cm) which is
at least four orders greater than the ferrites prepared by conventional method.
This larger value of resistivity attributes due to very small grain size and
successfully explained using the Verwey and deBoer hopping conduction model.
The contribution of grain and grain boundary resistance has been elucidated
using Cole Cole plot. The study of temperature dependent DC resistivity
confirms the semiconducting nature of all titled compositions wherein bandgap
(optical) increases from 2.73 eV to 3.25 eV with the increase of Yb content.
The high value of resistivity is of notable achievement for the compositions
that make them a potential candidate for implication in the high frequency
applications where reduction of eddy current loss is highly required.
