Effects of B_2O_3 Contents on Crystallization Behaviors and Dielectric Properties of CaO-B_2O_3-SiO_2 Glass Ceramics

摘要

The CaO-B_2O_3-SiO_2 glass ceramics system with four different boron contents(14 wt. %, 16.4 wt. %, 18.6 wt. %, 21 wt. %) were prepared under 900°C. The properties and microstructures are characterized by Differential Scanning Calorimeter(DSC), X-ray Diffraction(XRD) and Scanning Electron Microscopy(SEM). The effects of boron contents on the composition of crystalline phases and the properties of CaO-B_2O_3-SiO_2 glass ceramics system were studied. The results show that when the molar ratio of CaO/SiO_2 is 1.06, as the content of B_2O_3 increases, the major crystalline phases experiences the transformation from CaSiO_3 to CaB_2O_4 and the content of a-SiO_2 crystalline phase decreases, and the dielectric constant increases firstly but it decreases after the content of B_2O_3 reaches to 18.6 wt. %, while the dielectric loss tg5 of decreases gradually with the addition of boron content. When the content of B_2O_3 is 16.4 wt. %, the CaO-B_2O_3-SiO_2 glass ceramics with a bulk density of 2.47 g/cm~3 exhibits good dielectric properties(l MHz): ε_r=6.03, tgδ=3.49×10~(-3).