Microstructure and microwave dielectric properties of lead borosilicate glass ceramics with Al2O3

The effects of Al2O3 addition on both the sintering behavior and microwave dielectric properties of PbO-B2O3-SiO2 glass ceramics were investigated by Fourier transform infrared spectroscope (FTIR), differential thermal analysis (DTA), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results show that with the increase of Al2O3 content the bands assigned to [SiO4] nearly disappear. Aluminum replaces silicon in the glass network, which is helpful for the formation of boron-oxygen rings. The increase of the transition temperature T (g) and softening temperature T (f) of PbO-B2O3-SiO2 glass ceramics leads to the increase of liquid phase precipitation temperature and promotes the structure stability in the glasses, and consequently contributes to the decreasing trend of crystallization. Densification and dielectric constants increase with the increase of Al2O3 content, but the dielectric loss is worsened. By contrast, the 3% (mass fraction) Al2O3-doped glass ceramics sintered at 725 A degrees C have better properties of density rho=2.72 g/cm(3), dielectric constant E > (r) =6.78, dielectric loss tan delta=2.6x10(-3) (measured at 9.8 GHz), which suggest that the glass ceramics can be applied in multilayer microwave devices requiring low sintering temperatures.