Abstract
Al 2 O 3 ceramics are a candidate for millimeter-wave dielectrics. It possesses a high quality factor (Q·f) and a low dielectric constant (ϵ r ), however, a relatively large negative temperature coefficient of resonant frequency (τ f ) is an obstacle. For microwave communicating application, a τ f value near 0 ppm/°C is desirable to keep the frequency stability at various temperatures. On the other hand τ f of TiO 2 is positive value, indicating that the τ f can be improved by doping TiO 2 in Al 2 O 3 . However 0.9Al 2 O 3 -0.1TiO 2 sintered above 1350°C were composed of three phases: Al 2 O 3 , TiO 2 and Al 2 TiO 5 . The τ f value was about -20 –30 ppm/°C. By annealing in 1000–1100 °C, τ f value approached to be 0 ppm/°C with decomposition of AlTi 2 O 5 . A good Q·f was obtained by optimizing the annealing condition.
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