Effects of Si/B ratios on glass structure, crystallization and dielectric properties of CaO–SiO2–B2O3 glasses

Abstract

The glass structure, crystallization and dielectric properties of CaO–SiO2–B2O3 glasses with varying Si/B ratios (with constant Si/Ca ratio) have been investigated in this work. The density experimental results of glasses showed that the densities increased firstly and then decreased with the increasing Si/B ratios. The molar volumes of glasses increased slightly while oxygen densities of glasses decreased with the increasing of Si/B ratios. The FT-IR results of glasses revealed that the amounts of BIV units decreased while the (SiO4) tetrahedron increased with the increasing Si/B ratios. The DSC showed that the glass transition temperature Tg increased from 743 to 757 °C with increasing Si/B ratio. The crystallization activation energies (E) for CaSiO3 and CaB2O4 first increased until Si/B = 2.1 and then decreased slightly with the increasing Si/B ratio. For glass–ceramics samples sintered at 820 °C, all samples had the crystalline phases of CaSiO3 and CaB2O4 phases. The glass–ceramics sample with Si/B = 1.5 had the lowest dielectric constant er = 4.8.