Study on properties of BaxSmyTi7O20 ceramics with CaO-SiO2-B2O3 glass

The effect of CaO-SiO2-B2O3 (CSB) glass addition on the sintering temperature and dielectric properties of BaxSmyTi7O20 ceramics has been investigated using X-ray diffraction, scanning electron microscopy and differential thermal analysis. The CSB glass starts to melt at about 970 deg. C, and a small amount of CSB glass addition to BaxSmyTi7O20 ceramics can greatly decrease the sintering temperature from about 1350 to about 1260 deg. C, which is attributed to the formation of liquid phase. It is found that the dielectric properties of BaxSmyTi7O20 ceramics are dependent on the amount of CSB glass and the microstructures of sintered samples. The product with 5 wt% CSB glass sintered at 1260 deg. C is optimal in these samples based on the microstructure and the properties of sintering product, when the major phases of this material are BaSm2Ti4O12 and BaTi4O9. The material possesses excellent dielectric properties: εr = 61, tan δ = 1.5 x 10-4 at 10 GHz, temperature coefficient of dielectric constant is -75 x 10-6 deg. C-1