Improvement of the dielectric properties of rutile-doped Al2O3 ceramics by annealing treatment

The microwave dielectric properties of Al2O3 ceramics were studied. The objectives were to improve the large negative temperature coefficient of the resonant frequency (tauf) of Al2O3 ceramics and to obtain a relatively large quality factor (Qf) through the addition of rutile (TiO2), which has a large positive tauf, and an annealing treatment. A near-zero tauf (+1.5 ppm/C), excellent Qf (148000 GHz) and epsilonr (12.4) were obtained in 0.9Al2O3-0.1TiO2 ceramics sintered at 1350 C for 2 h, followed by annealing at 1100 C for 12 h in air. 12 refs.