Preparation and characterization of CoxMnmCrnNikFe3-(x+m+n+k)O4 ferrites and optimization of their structural and magnetic properties by Taguchi experimental design

Abstract

Powders of spinel type ferrite, CoxMnmCrnNikFe3-(x+m+n+k)O4, have been prepared by a coprecipitation method. The spinel type ferrite was obtained by pre-sintering at 200–1000 °C for 30–120 min in air. In order to optimize the conditions to prepare ferrites of the highest crystallinity, factors such as metal content, temperature and time of reaction, temperature and time of pre-sintering and concentration of NaOH were considered and optimized with Taguchi experimental design and regression analysis. Crystallinity was investigated by XRD analysis. Variation of crystallinity, the average size of crystallites, lattice constant, density and the initial permeability were studied against Mn, Cr and Ni contents. Characterization studies were made on the basis of IR, TG, UV-vis, EDX-SEM, XRF, AAS, XRD, and BET. It was found that the average size of crystallites is decreased when the crystallinity and initial permeability are increased. Some of the results obtained for the final samples were as follows: The X-ray density was 5.34 g cm-3, the lattice constant, a=0.83662 nm, the average size of crystallites was 87.9 nm, the BET surface area was 1.4 m2g-1 and the initial permeability was 36.14.