Preparation of Zn substituted Ni-Fe-Cr ferrites and study of the crystal structure by neutron diffraction

The spinel type solid solutions of ZnxNi1-xFeCrO4 (x = 0.2, 0.4, 0.6 and 0.8) were obtained by solid state sintering technique in air at 1523 K. X-ray and neutron powder diffraction experiments have been carried out on the samples at 295 K in order to characterize the materials. Rietveld refinement of the neutron diffraction data reveals that all the samples of the series possess cubic symmetry corresponding to the space group Fd3m. The distribution of Zn ions on the A and B sites as affected by the variation of x and also the distribution of Cr ions on the A and B sites have been determined. The Fe ions are distributed over both the A and B sites for the whole compositional range investigated. Only a small portion of the Ni ions are found to occupy the A site for x = 0.2, while all the Ni ions enter the B site for x greater than or equal to 0.4. The fractional coordinates of oxygen u, and the lattice parameter a, increase with increasing Zn content. The moment distributions in the two sublattices for different composition have been determined. (C) 2003 Elsevier Science B.V. All rights reserved.