The effect of CaO/SiO2 and B2O3 on the sintering contraction behaviors of CaO-B2O3-SiO2 glass-ceramics

Abstract

We investigate the effect of CaO/SiO2 (molar ratio) and B2O3 content on the structure and sintering contraction behaviors of Calcium borosilicate (CaO–B2O3–SiO2, CBS) glass-ceramic through the dilatometer and the Fourier transform infrared (FTIR) spectroscopy. The results show that the sintering-shrinkage of CBS glass-ceramics is promoted dramatically with the increase of CaO/SiO2 to 1.14, and then keeps nearly constant as the CaO/SiO2 further increases. This phenomenon is correlated with the degree of polymerization (DOP) of the Si–O network structure modulated by the CaO/SiO2, additionally, two sintering shrinkage peaks, corresponding to two-step depolymerization, are detected in the sintering-shrinkage curves of the CBS glass-ceramic as the B2O3 content is elevated to 13.6 mol%. Meanwhile, the shrinking rate of CBS glass-ceramics is increased from 8 × 10[Formula: see text] to 37 × 10[Formula: see text] min[Formula: see text] and the softening point is decreased from 736[Formula: see text]C to 691[Formula: see text]C with the increase of B2O3 content from 6.8 to 20.8 mol⋅%. This is due to the introduction of BO3 trihedral into Si–O–Si three-dimensional structure, which greatly reduces the uniformity and symmetry of the networks, inducing the decrease of the strength for the whole Si–O–Si network structures. The results obtained in this paper reveal the relationship between the glass structure and sintering behavior of the CBS glass-ceramic, which gives an avenue to improve its physical properties.