Molten salt synthesis, formation mechanism and greatly enhanced magnetic properties of randomly oriented BaM ferrite

Due to the influence of specific preparation process and product microstructure characteristics, it is a difficult task to prepare the randomly oriented BaFe12O19 (BaM) ferrite with large remanent magnetization (M-r) and high saturation magnetization (M-s), which hinder the practical application of the BaM ferrite. One of the means to solve this problem is to prepare well-developed hexagonal plate-like structure and single magnetic domain particles by lower synthesis temperature. In this study, the BaM ferrite were prepared using molten salt synthesis (MSS) method, and the preparation conditions of excellent magnetic properties and the formation mechanism of BaM ferrite synthesized by molten salt were discussed. Powder X-ray diffraction (PXRD), scanning electron microscope (SEM) and magnetic properties analyses indicated that the BaM ferrite with greatly enhanced magnetic properties could be obtained by adjusting the calcination temperature, Fe3+/Ba2+ molar ratio and the salts to reactants mass ratio R. The M-s and M-r of the prepared BaM ferrite were 71.9 emu/g and 39.5 emu/g, respectively. The Ms of the prepared BaM ferrite was significantly enhanced, and the Mr was much higher than that of BaM ferrite prepared by other methods. Using hydrothermal method synthesized spindle-like alpha-Fe2O3 as a raw material confirmed that the formation mechanism of molten salt synthesis of BaM ferrite was dissolution and precipitation mechanism. The formation of BaM ferrite underwent a series of processes including BaFe2O4 and BaFe4O7 formation, iron oxide dissolution, BaFe2O4 and BaFe4O7 desolvation of Ba2+, ion diffusion, nucleation growth and precipitation. (C) 2020 Elsevier B.V. All rights reserved.