Structural characterization and antistructure modeling of cobalt-substituted zinc ferrites

The cation distribution of the spinel system Zn1-xCoxFe2O4 (with x = 0; 0.1; 0.2; 0.3; 0.4; 0.5; 0.6; 0.7; 0.8; 0.9; 1.0) has been investigated by means of X-ray diffraction (XRD), Mossbauer spectroscopy and Fourier transform infrared spectroscopy (FTIR). In the present work, ferrites were prepared by co-precipitation method. XRD diffraction patterns show that all compositions have a pure single-phase cubic spinel structure over the whole composition range. It is found that both the lattice parameter and the average crystallite size decrease with increasing Co2+ content; from 8.4392 to 8.3536 angstrom and from 37 to 25 nm for ZnFe2O4 and CoFe2O4, respectively. Morphological observations (SEM, TEM) reveal that the crystallinity decreases significantly with increasing Co2+ content meanwhile the particle size becomes more uniform. The elemental compositional stoichiometry have been carried out by means of energy dispersive analysis (EDS). The force constants K-t and K-0 for the two sites have been deduced from IR band frequencies and compared with the trend of bond lengths: KT increases (from 2.084 to 2.144 dyn/cm(2)) because the bond length M-A-O decreases, while K-o decreases (from 1.043 to 0.948 dyn/cm(2)) because the bond length M-B-O increases with increasing Co2+ content. For the first time antistructural modeling of zinc-cobalt ferrites considered. It shown that the acceptor in crystall latice is tetrahedral iron FeA(center dot), while the donor is octahedral cobalt Co-B('). With increasing Co2+ content, the concentration of active centers in tetrahedral and octahedral sublattice of zinc-cobalt ferrites are increases. The nature of the active centers are affecting on the chemical, electrical, magnetic, optical and catalytic properties of ferrites. (C) 2016 Elsevier B.V. All rights reserved.