S. Agrawal
NIT RAIPUR,
India
Keywords: auto combustion method, dielectric properties, grain and grain boundaries, chromites, activation energy
Summary:
In this paper, MgFexCr2-xO4 (0, 0.2 and 0.4 mol%) chromites have been synthesized by solution-combustion route and its electrical and dielectric properties have been investigated. The XRD analysis revealed that the MgFexCr2-xO4 chromites crystallized into single phase fcc cubic crystal (Fd-3m space group) symmetry with estimated crystallite size ranging from 19.65 nm – 25.66 nm calculated using Scherrer formula. Using TEM analysis, the surface morphology of the particles was investigated. The presence of all the elements and its elemental composition (atomic % and weight %) were obtained by EDX spectroscopy. FTIR spectra showed two bands around 458.86 cm-1 – 463.56 cm-1 and 578.17 cm-1 – 594.86 cm-1, which are associated with stretching and bending vibrations of metal-oxide (Mg – O & Cr – O) bonds, respectively. Based on Jonscher’s power law and quantum mechanical tunneling (QMT), the frequency dispersion AC conductivity of MgFexCr2-xO4 chromites was investigated. Activation energy was calculated and found in the range of 0.29 eV – 0.51 eV using Arrhenius equation. The non – Debye relaxation and NTCR behaviour of chromites were studied using complex impedance spectroscopy (CIS). The frequency dispersion dielectric parameters (ε’ and ε’’) have been explained using Maxwell – Wagner model on the basis of space charge polarization and hopping of electron between Cr2+ and Cr3+ ions. The obtained values suggest that the utilization of material is in electronic devices and other energy storage applications.