Effects of B₂O₃ content on crystallization behavior and properties of low temperature co-fired CaO-B₂O₃-SiO₂ glass-ceramics

The CaO-B₂O₃-SiO₂ (CBS) glass-ceramics with different B₂O₃ content were prepared by glass melt quenching followed by sintering method. The crystallization behavior and dielectric properties of CBS glass-ceramics were systemically investigated. The thermal properties and flexural strength of CBS glass-ceramics were also characterized. Results show that the main crystal phases of each composition are CaSiO₃, SiO₂ and CaB₂O₄. Quantitative analysis of the crystal phase found that B₂O₃ content stimulates the formation of CaB₂O₄ phase but inhibits the generation of CaSiO₃ phase. In addition, the B₂O₃ content also acts on the properties of CBS glass-ceramics. In this study, the 41CaO-41SiO₂-18B₂O₃ (mol%) sample sintered at 900 °C for 15 min has the optimum properties: the density of 2.65 g/cm³, a moderate dielectric constant of 6.13, a low dielectric loss of 1.6 × 10^–3 (10 GHz), the thermal expansion coefficient of 8.79 ppm/K, the thermal conductivity of 2.85 W/m/K, a high flexural strength of 191.0 MPa. Such glass-ceramics with high flexural strength and excellent dielectric properties have good development prospect for LTCC applications.