Influence of Yb3+ on the structural, electrical and optical properties of sol–gel synthesized Ni-Zn nanoferrites

Abstract

Polycrystalline Yb-substituted Ni-Zn 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 (52–18 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 1010 Ω-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 Nyquist/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.