Low-temperature synthesis of nanocrystalline NiCuZn ferrite and the effect of Cr substitution on its electrical properties

Abstract

In this study, nano-sized ferrites of compositions (Ni 0.6 Cu 0.20 Zn 0.20 Fe 2− x Cr x O 4 ), where x =0–1.0, were synthesized through nitrate–citrate auto-combustion method at relatively low temperature. XRD revealed the formation of nano-sized ferrite particles with cubic spinel structure. An exception was obtained for samples with Cr content ≤0.2, where weak diffraction peaks attributed to the presence of CuO and Fe 2 O 3 were appeared. The average crystallite sizes are much dependent on the chromium content and were found to decrease with its increase. The lattice parameter ( a ) slightly decreases with Cr substitution, which can be explained on the basis of the relative ionic radii of Cr 3+ and Fe 3+ ions. X-ray density was found also to decrease slightly with increase in chromium content, which indicates lower densification by the addition of Cr. FT-IR measurements show the characteristic ferrite bands. The Mössbauer spectra varied from Zeeman sextets to a relaxed doublet by increase in Cr content, which indicates a decrease in the hyperfine field at the octahedral site. Electrical property measurements revealed that Cr 3+ ions do not participate in conduction process but limit the degree of Fe 3+ –O 2− –Fe 3+ conduction resulting in a decrease in the conductivity and increase in conduction activation energy.