Microstructures and Microwave Dielectric Properties on Annealed Al2O3-TiO2 Composite Ceramics
The large negative temperature coefficient of resonant frequency ( τ f ) of Al2O3 is a problem for applicable microwave/millimeter wave dielectrics. A Previous study reported that the τ f was improved by sintering with TiO2 and then annealing, where the annealing decompose the secondary phase of Al2TiO5. This study investigated the hold time of annealing. The Quality factor (Qf ) value decreased when the sample was annealed at 1100°C for 2hrs. While Al2TiO5 was not detected by X-ray powder diffraction, it was located around TiO2 by scanning transmission electron microscopy equipped with energy dispersive X-ray spectroscopy. It should be considered that the degradation of the Qf was caused by the existence of noncrystalline Al2TiO5 and new boundaries between noncrystalline Al2TiO5 and TiO2.
Kazumi Kato, Tadashi Takenaka, Masasuke Takata and Kazuo Shinozaki
Y. Miyauchi et al., "Microstructures and Microwave Dielectric Properties on Annealed Al2O3-TiO2 Composite Ceramics", Key Engineering Materials, Vol. 388, pp. 251-254, 2009