Low-temperature sintering and microwave dielectric characteristics of Ba2Ti9O20 ceramics

The effect of B2O3 and BaB2O4 additions on the low-temperature sintering and the microwave dielectric characteristics of Ba2Ti9O20 have been investigated. The amounts of B2O3 and BaB2O4 were varied from 1 to 10 wt.% and the green compacts were sintered in the temperature range of 900–1100 °C for 2 h. As the amount of B2O3 increased, the bulk density decreased. In contrast to B2O3 addition, the density increased with the amount of BaB2O4. From the X-ray analysis of the sintered specimens, it was found that the borides of B2O3 and BaB2O4 promoted the formation of Ba2Ti9O20 phase. Second phases of BaTi(BO3)2 and TiO2 were observed when B2O3 was added. When BaB2O4 was added, however, TiO2 was not observed regardless of the amount of BaB2O4. Dielectric characteristics were also examined and discussed in correlation with the densification, microstructure, and the second phase development.