Rapid synthesis of nickel ferrite nanoparticles by the molten salt method

Abstract It is presented a ‘shocking thermal treatment’ methodology as a modification to the molten salts process to rapidly obtain pure phase nickel ferrite nanoparticles within a high-scalable green synthesis scheme. Analysis from x-ray diffraction and electron microscopy (SEM and TEM) confirms the formation of the nanostructures, with the most frequent crystallite sizes between 55–85 nm. Room temperature magnetic characterization, from Mössbauer spectroscopy and magnetic measurements M(H), evidences their superparamagnetic distribution with a magnetic saturation of 47.9 emu g⁻¹. An approximated stoichiometry of {({Ni}_0.03{Fe}_0.97)}_A{({Ni}_0.97{Fe}_1.03)}_B{O}₄ was proposed from Rietveld refinement, Mössbauer and energy-dispersive x-ray spectroscopies. The effect on the electronic structure due to the shocking thermal treatment was elucidated by estimating the optical band gap with values between 1.78 and 2.38 eV.