Structural, Morphological, Optical and Magnetic Properties of Al-Doped CoFe2 O 4 Nanoparticles Prepared by Sol–Gel Auto-Combustion Method

Abstract

CoFe2−xAlxO4 (x = 0.0,0.5,1.0, and 1.5) ferrite nanoparticles have been synthesized by the sol–gel auto-combustion method. The effect of non-magnetic Al content on their structural, morphological, optical, and magnetic properties was also investigated. X-ray diffraction (XRD) diffraction analysis was applied and indicated that the synthesized nanopowders of samples with x<1.5 and calcined at 800 ∘C have single-phase spinel structure. It has shown also by increasing Al content, the particle size, lattice parameter, unit cell volume, coercivity, anisotropy constant, and magnetization decrease, while the energy band gap increases. The size of particles was measured by TEM being in the range of 65–75 nm (for x = 0.0) and 9–10 nm (for x = 1.0). For sample with x = 1.5, the minimum calcination temperature for obtaining a single-phase spinel structure was 1000 ∘C. By increasing the calcination temperature from 1000 to 1100 ∘C, the mean crystallite size and crystallinity increase, while the lattice parameter, coercivity, anisotropy constant, and magnetization decrease. The average grain size evaluated by SEM analysis was found to be \(\tilde 91\) and 166 nm for samples calcined at 1000 and 1100 ∘C, respectively.