Sintering and microwave dielectric properties of LTCC-zinc titanate multilayers

The effects of ZnO–B₂O₃–SiO₂ (ZBS) on the sintering behavior and microwave dielectric properties of ZnO–TiO₂ system were investigated as a function of ZBS content and sintering temperature. Densities of the specimens were enhanced with an increase of ZBS up to 2 wt.% and then decreased. X-ray diffractometry analyses results indicated that the phase stability region of the hexagonal ZnTiO₃ extended to lower temperatures as the amount of ZBS increased. The dielectric properties of ZnO–TiO₂ system with ZBS are strongly dependent on the sintering conditions, especially near the phase decomposition temperature. The sintering temperature of the specimens could be reduced to 900 °C without the degradation of the microwave dielectric properties. From 900 °C, the temperature compensation characteristics occurred as the phase composition changed from ZnTiO₃ to two phases: Zn₂TiO₄ and rutile. The dielectric constant (ɛ_r) increased and Q×f value decreased due to the phase decomposition. The ɛ_r value of 27, Q×f value of 19,396 (at 6 GHz) and τ_f value of 2 ppm/°C were obtained for ZnO–TiO₂ ceramics with 2.0 wt.% ZBS sintered at 900 °C for 3 h. The low-temperature sintering ceramics powders were suitable for the tape casting process. Also, the material is compatible with Ag electrodes and, therefore, is suitable for LTCC application.