Sintering and dielectric properties of 0.88Al2O3–0.12TiO2 microwave ceramics by glass addition

The microwave characteristics and the microstructures of 0.88Al2O3–0.12TiO2 with various amounts of MgO–CaO–SiO2–Al2O3 (MCAS) glass sintered at different temperatures have been investigated. The sintering temperature can be lowered to 1300 °C by the addition of MCAS glass. The densities, dielectric constants (εr) and quality values (Q×f) of the MCAS-added 0.88Al2O3–0.12TiO2 ceramics decrease with the increase of MCAS glass content. The temperature coefficients of the resonant frequency (τf) are shifted to more negative values as the MCAS content or the sintering temperatures increase. The change of the crystalline phases of Al2TiO5 phase and rutile-TiO2 phase has profound effects on the microwave dielectric properties of the MCAS-added Al2O3–TiO2 ceramics. As sintered at 1250 °C, 0.88Al2O3–0.12TiO2 ceramics with 2 wt.% MCAS glass addition exists a εr value of 8.63, a Q×f value of 9578 and a τf value of +5 ppm/°C.