Sintering,crystallization and dielectric properties of CaO-B2O3-SiO2 system glass ceramics

CaO-B2O3-SiO2 (CBS) glass powders are prepared by conventional glass melting method at different melting temperatures, whose properties and microstructures are characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). It is found that there are SiO2 and some unknown phases in CBS glass melting liquid from 1 300 °C to 1 500 °C and the amount of these phases decreases with the increase of the melting temperature. The CBS glass melted at 1 450 °C could be sintered from 830 °C to 930 °C and the bulk densities of the samples are all higher than 2.4 g/cm3. From the points of the properties and energy conservation, the melting temperature of 1 450 °C is the optimal melting temperature. The glass ceramic sintered at 850 °C exhibits better dielectric properties:εr=6.33, tan δ=2.2×10-3 at 10 GHz, and the major phases of the samples are CaSiO3, CaB2O4 and SiO2.