Effects of Nd/Sm ratio and glass addition on the microwave dielectric properties of Ba4.5(Sm(0.8−x)NdxBi0.2)9Ti18O54 ceramics

In this study, Ba4.5(Sm(0.8−x)NdxBi0.2)9Ti18O54 ceramics with various amounts of glass were prepared. The effects of Nd/Sm ratio and glass content on the microstructure evolution and microwave dielectric properties were evaluated. SEM micrographs revealed that the microstructures of Ba4.5(Sm(0.8−x)NdxBi0.2)9Ti18O54 ceramics with 4 wt.% glass sintered at 1150 °C are uniform and their grain sizes range from 1 to 3 μm. The dielectric constant of Ba4.5(Sm(0.8−x)NdxBi0.2)9Ti18O54 ceramics increased with increasing sintering temperature or the Nd content, and the τf value also increases with increasing Nd content. With 6-10 wt.% glass added, Ba4.5(Sm0.24Nd0.56Bi0.2)9Ti18O54 ceramics obtain maximum densities at 1100 °C. No second phase was detected in the XRD patterns. Grains are columnar-like and grain size increases significantly with increasing glass content and sintering temperature. The results showed that Ba4.5(Sm0.24Nd0.56Bi0.2)9Ti18O54 ceramics with 2 wt.% glass sintered at 1150 °C had a sintering density of 5.6 g/cm3, dielectric constant of 87.9, Q·f of 2523 GHz, and τf of 22.8 ppm/°C.