Magnetic properties of B₂O3-SiO₂-BaO-Fe₂O₃ glass-ceramics

• The structural investigation of B₂O3-SiO₂-BaO-Fe₂O₃ glass-ceramics was investigated.
• The effect of BaO/Fe2O3 ratio on structure of B₂O3-SiO₂-BaO-Fe₂O₃ was investigated.
• The effect of annealing on structure of B₂O3-SiO₂-BaO-Fe₂O₃ was investigated.
• The effect of annealing on magnetic properties of B₂O3-SiO₂-BaO-Fe₂O₃ was investigated.

The magnetic characterization of B2O3-SiO2-BaO-Fe2O3 glass-ceramics during annealing process was the goal of this study. In this regard, different mixtures of BaO, Fe₂O₃, SiO₂ and B₂O3 were melted and then quenched between two cold steel sheets. The annealing process was done in as-quenched samples in temperature range of 550 to 850 °C for different periods of time. The prepared samples were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and vibrating scanning magnetometer (VSM). According to achieved results, fully amorphous structure can only be formed in 20B2O3-10SiO2-45BaO-25Fe2O3 system and the microstructures of as-quenched samples in other systems were combination of Fe3O4, BaFe12O19 and amorphous phases. The coercivity and saturation of magnetization of as-quenched samples were estimated about 85–120 Oe and 12–17 emu/g, respectively. By annealing the produced samples, the coercivity value was increased to about 3100 Oe as a result of precipitation of BaFe12O19 in nonmagnetic Ba2FeSi2O7 matrix. The highest value of coercivity was achieved in annealed sample at 700 °C for 5 h.

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