Crystallization kinetics and the dielectric properties of SrO-BaO-Nb₂O₅-B₂O₃ glass-ceramics

Glass-ceramics materials of SrO-BaO-Nb₂O₅-B₂O₃ system have been prepared by conventional melt-casting followed by controlled crystallization. The crystallization kinetics, phase evolution, microstructure, breakdown strength and dielectric properties have been explored by differential scanning calorimetry (DSC), X-ray diffractometer (XRD), scanning electron microscope (SEM), and multifunction LCR meter. The results reveal that crystallization mechanism of this glass is believed to be three-dimensional interfacial growth. It was observed that predominant crystalline phase is Ba_0.39Sr_0.61Nb₂O₆ in these glass-ceramics crystallized at 750 °C, and the grain size increases with increase in crystallization time. The uniform microstructure can be seen clearly in glass-ceramics crystallized at 750 °C for 3 h, and the obtained glass-ceramics was found to possess optimal properties. Moreover, glass-ceramic with a dielectric constant of 58, the dielectric loss of 0.007 and breakdown strength of 1010 kV/cm could be achieved. In addition, energy storage density of glass-ceramics reached a maximal value of 2.62 J/cm³. To our knowledge, studies on SrO-BaO-Nb₂O₅-B₂O₃ glass-ceramics without SiO₂ as a glass network former are few, and the melting temperature of the B₂O₃-based glass is lower than that of SiO₂-based glass, which is conducive to the purpose of energy saving. These findings indicate that this glass may be a candidate for high energy-storage capacitors.