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 BaB₂ O₄. Dielectric characteristics were also examined and discussed in correlation with the densification, microstructure, and the second phase development.