Preparation of the LTCC composite ceramics with low permittivity

In this work, the LTCC composite ceramics containing α-alumina and quartz based on the binary system BaO–B₂O₃ were prepared by traditional solid-state preparation process at a sintering temperature of 900 °C. Sintering mechanism and physical properties of the LTCC composite ceramics are investigated and discussed in detail in terms of their mineral phase composition. The results indicate that, by the chemical combination of barium hydroxide octahydrate and an aqueous solution of boric acid, a barium borate phase can be formed form the binary system BaO–B₂O₃ and consequently supply a liquid sintering aid for the fabrication of LTCC composite ceramics at a sintering temperature of 900 °C. The introduction of α-alumina to the binary system BaO–B₂O₃ can improve the sintering behavior whereas the presence of quartz in the composite ceramics is important to achieve low permittivity. By the combination of α-alumina, quartz and BaO–B₂O₃ composition, the dense LTCC composite ceramics, which is characterized by excellent dielectric properties (permittivity: 3.56; 4.83; dielectric loss: 3 × 10⁻⁴; 4 × 10⁻⁴), can be fabricated availably.