The effects of B2O3 content and Ca/Si ratio on the densification behavior and microwave dielectric properties of the CaO-B2O3-SiO2 glass-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 degrees C to 691.5 degrees 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 epsilon(r) from 5.563 to 6.469 and decrease of tand from 1.99 x 10(-3) to 1.54 x 10(-3). Especially, the CBS glass-ceramics with Ca/Si ratio of 1.20 and B2O3 content of 16.5 mol% sintered at 850 degrees C for 30 min exhibited excellent microwave dielectric properties, with epsilon(r) similar to 6.092 (@11.37GHz), tan delta similar to 9.69x 10(-4) and Qxf similar to 11737.47 GHz, tau(f) similar to -17 ppm/degrees C, which are attractive for LTCC substrate application.