Fine particles of lanthanum-and cobalt-doped strontium hexaferrite prepared through glass crystallization

Glass of nominal composition Sr0.6La0.4Fe11.6Co0.4O19 + 12SrB2O4 was prepared by rapidly quenching an oxide melt and was then heat-treated at temperatures from 550 to 900°C to give glass-ceramics containing fine lanthanum-and cobalt-doped strontium hexaferrite particles and microcrystalline SrB2O4. The materials were characterized by x-ray diffraction, scanning electron microscopy, electron probe x-ray microanalysis, and magnetic measurements. The coercivity of the glass-ceramic samples was shown to increase up to 427 kA/m with increasing heat-treatment temperature. The saturation magnetization of the samples increases up to 25.0 A m2/kg as the heat-treatment temperature is raised to 750°C, and decreases slightly at higher temperatures. Dissolving the nonmagnetic matrix of the glass-ceramic prepared at 900°C, we obtained submicron powder of composition Sr0.88La0.12Fe10.74Co0.47Oy, as determined by x-ray microanalysis.