Microstructure and properties of calcium borosilicate composite glass-ceramics sintered at low temperature

Calcium borosilicate (CaO-B₂O₃-SiO₂, CBS) glass based composite glass-ceramics were prepared by adding borosilicate glass. The effects of borosilicate glass and sintering temperature on the properties of the glass-ceramics were investigated. The relationships between properties and structures were studied by X-ray diffraction and scanning electron microscope. The results show that the two glasses are compatible with each other with the borosilicate glass content of 10%-40% (in mass, the same below). The composite powders of the two glasses could be sintered at a low temperature (850°C). Due to the introduction of borosilicate glass, α-SiO₂ with a low dielectric constant and high thermal expansion coefficient (CET, α) was formed. The relative dielectric constant (ε_r) decreases with increasing the borosilicate glass content, and it can be adjusted between 5.6-6.6. The α increases slowly when the borosilicate glass content is less than 20% and increases rapidly when the content ranges from 30% to 40%. Increasing the sintering temperature can promote crystallization. The dielectric constant decreases as the sintering temperature increases because the crystal has a lower constant than CBS glass.