The effects of B₂O₃content and Ca/Si ratio on the densification behavior and microwave dielectric properties of the CaO-B₂O₃-SiO₂glass-ceramics for LTCC application

In this work, the sintering behavior, crystallization, densification, and microwave dielectric properties of CaO-B2O3-SiO2 (CBS) glass-ceramics have been systematically studied with different Ca/Si ratios and B2O3 contents. TMA curves demonstrated that with increasing B2O3 content from 1.5 mol% to 16.5 mol%, the softening temperature (TS) was decreased from 776.5 °C to 691.5 °C, and the shrinking rate was increased from 13.81% to 30.32%, then decreased to 11.25%. With further increasing Ca/Si ratio from 1 to 1.30, the sintering behavior was greatly improved with the linear shrinkage increasing from 11.25% to 53.22%, which led to the increase of ϵr from 5.563 to 6.469 and decrease of tanδ from 1.99 × 10-3 to 1.54 × 10-3. Especially, the CBS glass-ceramics with Ca/Si ratio of 1.20 and B2O3 content of 16.5 mol% sintered at 850°C for 30 min exhibited excellent microwave dielectric properties, with ϵr ~ 6.092 (@11.37GHz), tanδ ~ 9.69× 10-4 and Q×f ~ 11737.47 GHz, τf ~ -17 ppm/°C, which are attractive for LTCC substrate application.