Densification and microwave dielectric behaviors of CaO–B2O3–SiO2 glass-ceramics prepared from a binary glass composite

In this study, a binary CaO–B2O3–SiO2 (CBS) glass composite CBS 950 comprising a high SiO2 content (67.3 mol%) and a low SiO2 content (23.3%) of CaO–SiO2–B2O3 glasses was prepared. The sintering behavior, structural evolution, and dielectric properties of the binary glass composite were characterized and compared to those of a single CBS glass (CBS-11) with the exact same composition. CBS-11 glass densified rapidly within a narrower temperature range (≈800 °C) as compared to CBS-950 glass (from ≈700 °C to 875 °C). It was found that crystallization of CaB2O4 phase in CBS-950 glass was easier than that in CBS-11 glass during heat treatment. Activation energy of CaB2O4 phase in CBS-950 glass was determined to be 307 kJ/mol. The best glass-ceramic was resulted from CBS-950 glass sintered at 900 °C, which possesses a dielectric constant of 3.77 and a dielectric loss of 0.0012 at frequency of 4.3 GHz. CBS-950 glass is superior to CBS-11 glass for use as LTCC substrates in terms of overall performance.