Effect of High-Energy Ball Milling on Molten Salt Synthesized Barium Hexaferrite Powder

Abstract

M-type hexagonal ferrite powder was prepared by the molten salt flux method calcined at a relatively low temperature (850 °C) with a product yield of 99.87%. The synthesized sample was then milled for 3 h by high-energy ball milling in toluene suspension to obtain ultrafine nanoparticles. The structural, morphological, and magnetic properties of the particles were investigated to observe the effect of milling on the molten salt synthesized powder. The analyses reveal the presence of barium hexaferrite (BaFe12O19) as the main phase with less impurities. Average crystallite size, determined by X-ray diffraction (XRD), decreased from 81 ± 20 nm to 52 ± 5 nm after ball milling. The Fourier transform infrared (FTIR) spectra ensure the tetrahedral and octahedral positions in barium hexaferrite structure with an increase in the intensity of absorption bands after milling. The electron paramagnetic resonance (EPR) signal shows a broad line that demonstrates a decrease in the amplitude of the milled sample. Furthermore, remanence measured by vibrating sample magnetometer (VSM) increases from 8.5 to 25 emu/g. A 72% increase in coercivity and 84% increase in magnetic saturation is observed for the milled samples compared to that of pure BaFe12O19 (unmilled). The variations of the magnetic properties are thus attributed to the reduction in crystalline size and lattice parameters after milling.