Characterization and analysis of CaO–SiO2–B2O3 ternary system ceramics

The dielectric, thermal and mechanical properties of CaO–SiO2–B2O3 ternary system ceramics by solid-phase method have been carried out and quantitive analysis been examined by X-ray diffraction (XRD) patterns. The results showed that the major crystalline phase of CaO–SiO2–B2O3 ternary system ceramics was wollastonite (about 90 wt%) which existed at the temperature ranging from 950 to 1,100 °C. It is also observed that wollastonite could be transformed to pseudowollastonite at 1,200 °C. In addition, with increase in calcination temperature, the amount of wollastonite increases. When the sintering temperature is at 1,100 °C, the amount of wollastonite has a maximum value of 92.7 wt%. Accordingly, CaO–SiO2–B2O3 ternary system ceramics achieved excellent properties at 1,100 °C, such as dielectric constant of 8.38, dielectric loss of 1.51 × 10−3 at 1 MHz, linear thermal-expansion coefficient (300 K) of 6.68 × 10−6/K, bending strength of 121.75 Mpa. Analysis of the mechanical and dielectric properties showed that the measured bending strength, dielectric constant and loss of CaO–SiO2–B2O3 ternary system ceramics can be substantially modified and improved by controlling the sintering temperature, in particular due to the amount of wollastonite crystalline phase and size of grains.