Crystallization of a SrO-B2O3-SiO2-Fe2O3 glass was investigated to elucidate the precipitation process of SrFe12O19 from the glass matrix.
The results obtained are as follows; an unidentified crystal phase, X-phase, precipitates by heating the glass in the temperature range from Tg (546°C) to 750°C. The X-ray diffraction lines of the X-phase are well indexed with assuming a cubic unit cell with α=7.584Å. In the temperature range from 650°C to 750°C, 4SrO⋅B2O3⋅SiO2 precipitates in the vicinity of the glass surface and gradually grows toward the inside of the glass.
SrFe12O19 co-precipitates with 4SrO⋅B2O3⋅SiO2 in the temperature range from 750°C to 850°C. 4SrO⋅B2O3⋅SiO2 has crystallized rapidly in the whole region of the glass and no X-phase is observed in that temperature range. The amount of SrFe12O19 with heating time changes relatively in the same manner as that of 4SrO⋅B2O3⋅SiO2. Based on these results, hexagonal platelets of SrFe12O19 with a dimension of%cong; 0.3μm are obtained as a precipitate from the glass by the heat-treatment at 800°C for 5 hr.