Effect of Ho3+ Ion Doping on Thermal, Structural, and Morphological Properties of Co–Ni Ferrite Synthesized by Sol-Gel Method

Abstract

Rare earth Ho3+-substituted Co–Ni ferrites having a chemical formula Co0.6Ni0.4Fe2−xHoxO4 (0.0, 0.025, 0.05, 0.075, and 0.1) were prepared via sol-gel route. The phase formation of these samples was confirmed by the thermogravimetric analysis with differential thermal analysis and X-ray powder diffraction techniques. Rietveld refinement confirms the cubic spinel structure of the prepared samples having space group Fd3− m with presence of secondary phase of α-Fe2O3. The lattice parameter is increased from 8.412 to 8.582 A with Ho3+ ion concentration in cobalt–nickel ferrite from x = 0 to x = 0.1. The distribution of cations has been studied with the help of X-ray diffraction data and it is found that Ho3+ ions preferred to occupy the octahedral [B] site. The other structural parameters like X-ray density, bulk density, hopping length, and allied parameter are increased with the composition of Ho3+ ions in the Co–Ni ferrite. The morphology of the samples was observed by transmission electron microscopy and scanning electron microscopy showed the nanostructured formation.