Effect of boron on crystallization, microstructure and dielectric properties of CBS glass-ceramics

Herein, we demonstrate the preparation of CBS glass-ceramics by using chemically pure CaO, SiO2 and B2O3 as raw materials. Differential scanning calorimetry (DSC), X-ray diffraction (XRD), scanning electron microscopy (SEM), and electrical measurements have been carried out to explore the effect of boron addition on crystallization, microstructure and dielectric properties of CBS glass-ceramics. Furthermore, the influence of sintering temperature and sintering schemes has been systematically investigated. Results show that the increase of boron content reduces crystallization temperature of CBS glass-ceramics. For instance, with the increase of boron oxide from 10.8 wt% to 19.4 wt%, crystallization temperature decreased by 130 °C. However, excessive boron affects the precipitation of wollastonite crystal phase, destroys crystal structure and damages close arrangement of crystal grains. Moreover, higher boron content weakens dielectric properties of CBS glass-ceramics. In this study, the best molar ratio of ingredients, meeting the ideal target material, is n(Ca): n(Si): n(B) = 1:1:0.6. After optimal sintering procedure, dielectric constant of the best sample was 6 (1 MHz), 6 (10 MHz), and dielectric loss was 2.27 × 10−3 (1 MHz) and 3.37 × 10−3 (10 MHz). We demonstrate that the optimal boron content and sintering procedure is required to attain desired dielectric properties of CBS glass-ceramics.