Rietveld structure refinement, cation distribution and magnetic properties of Al3+ substituted NiFe2O4 nanoparticles

Abstract

Ferrite samples of Al3+ substituted NiFe2O4 nanoparticles were prepared by wet chemical co-precipitation method. The samples were obtained by annealing at relatively low temperature at 600 °C and characterized by x-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), vibrating sample magnetometry (VSM), and ac susceptibility. On applying the full pattern fitting of Rietveld method using FullProf program, exact coordinates of atoms, unit cell dimensions, atom ion occupancy, degree of inversion as well as crystallite size and residual microstrain have been determined. The lattice parameter, density, particle size, lattice strain, magnetization, magneton number, and Curie temperature are seen to decrease with increasing A13+ content whereas the specific surface area, porosity, coercive force, shows an increasing trend with A13+ content. Cation distribution is obtained from XRD and Rietveld method and the variation of the cation distribution has been discussed on the basis of site preference, size and valence of the substituting cations. The variation of the magneton number with the Al3+ content is satisfactorily explained on the basis of Néel’s collinear spin ordering model. Curie temperature of all the compositions are also obtained theoretically and it agrees with observed Curie temperature.

Nickel on alumina catalysts for the production of hydrogen rich mixtures via the biogas dry reforming reaction: Influence of the synthesis method

“…It was suggested that the observed reduction peaks, as well as their position could be related to the different Ni 2þ coordination in the spinel framework. Furthermore, they concluded that as the contribution of the b-peak in the total Ni species present in the spinel structure of NiAl 2 O 4 -CD was lower (27%) than that of NiAl 2 O 4 -CP (51%), the Ni 2þ ions occupying octahedral sites were more prone to reduction than the tetrahedral ones, as in the case of our 8NiAl-edf catalyst Thus, such results strongly support that the reforming efficiency is highly dependent on the type of interaction of the Ni active phase with the carrier [38,81,82].…”

The role of pH on the particle size and magnetic consequence of cobalt ferrite

“…The small deviation between a th and a exp may be due to the presence of some ferrous ions Fe (II) ( ) on octahedral sites with larger radii than Fe (III) ( ) [23]. Using the values of "a", the radius of oxygen ion, , and r A in the following expression, the oxygen positional parameter 'u' can be calculated [24]:…”

Cation distribution and Mössbauer spectral studies of Mg0.2Mn0.5Ni0.3InxFe2−xO4 ferrites (x=0.0, 0.05 and 0.10)

“…Fe 3+ and Mn 2+ ions randomly occupy A-site and B-site, non-magne tic Mg 2+ ions strongly prefer B-site and partially occupy A-site [35], Ni 2+ ions have strong preference to occupy B-site [36]. For the smaller concentr ation, In 3+ ions initially go to tetrahedral A-site and it prefer B-site for the higher concentratio n. Redistribution of the cations to less preferred sites has been considered only when required by calculated value of Fe occupancy of A and B sites.…”