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 (ɛr) increased and Q×f value decreased due to the phase decomposition. The ɛr value of 27, Q×f value of 19,396 (at 6 GHz) and τf 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.