Effect of Cr3+ substitution on properties of nano-ZnFe2O4

Abstract

Nano-crystalline ferrite materials with general formula ZnCrxFe2−xO4 (x=0.1, 0.2, 0.3, 0.4 and 0.5) have been synthesized by chemical co precipitation method. The developed materials were characterized for structural, shape/size and electrical properties by using analytical techniques viz. X-ray diffraction (XRD), transmission electron microscopy (TEM), and impedance analyzer respectively. X-ray diffraction pattern confirms the formation of single phase spinel structure of prepared ferrites. The lattice constant of ZnCrxFe2−xO4 (x=0.1, 0.2, 0.3, 0.4 and 0.5) nano-particles decreases with increasing Cr3+ ion content. Nano-size of synthesized ferrite particles were confirmed by electron microscopy. DC-electrical conductivity and activation energy increases with increasing Cr3+ ion content. Dielectric loss (tanδ), real part of dielectric constant (ɛ′), imaginary part of dielectric constant (ɛ″), ac conductivity (σac), real (resistive) part of impedance (Z′) and imaginary part of impedance (Z′′) were analyzed as a function of frequency, composition and temperature using impedance analyzer in the frequency range of (1KHz–5MHz) and temperature range of (300–523K). Dielectric loss (tanδ), dielectric permittivity (ɛ′) and ac conductivity (σac) decreases with increase in Cr3+ substitution which has been explained on the basis of hopping mechanism. Electrical conductivity increases with increasing temperature revealing the semiconducting behavior of prepared ferrites as also observed by the variation in cole–cole plots with temperature. The Nyquist impedance plots of the prepared ferrites clearly reveal the inherent phenomenon involved in conduction mechanism of Cr3+ substituted ZnFe2O4 ferrites.