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

Abstract The magnetic characterization of B 2 O 3 -SiO 2 -BaO-Fe 2 O 3 glass-ceramics during annealing process was the goal of this study. In this regard, different mixtures of BaO, Fe₂O₃, SiO₂ and B₂O 3 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 20B 2 O 3 -10SiO 2 -45BaO-25Fe 2 O 3 system and the microstructures of as-quenched samples in other systems were combination of Fe 3 O 4 , BaFe 12 O 19 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 BaFe 12 O 19 in nonmagnetic Ba 2 FeSi 2 O 7 matrix. The highest value of coercivity was achieved in annealed sample at 700 °C for 5 h.