Synthesis and Magnetic Properties of SrO–Fe2O3–B2O3–Bi2O3 Glass-Ceramics

Glass of nominal composition SrFe12O19 + 12SrB1.5Bi0.5O4 is prepared by rapid quenching from the liquid state and is converted to glass-ceramics containing fine SrFe12O19 particles by heat treatment between 600 and 850°C. The materials are characterized by Mössbauer spectroscopy, x-ray diffraction, differential thermal analysis, electron microscopy, and magnetic measurements. All of the Fe in the glass is shown to be in the oxidation state 3+. The phase transformations accompanying glass crystallization are identified. The coercive field of the samples is shown to increase from 188 to 504 kA/m as the heat-treatment temperature is raised from 600 to 850°C. The composite prepared by heat treatment at 850°C contains submicron-sized SrFe12O19 particles with a thickness-to-diameter ratio of 0.33.