The microstructure and the microwave dielectric properties of nano-scaled a alumina (alpha-Al2O3) ceramics with various added amounts of nano-scaled TiO2 have been investigated. The sintering temperature of nano-scaled alpha alumina can be effectively lowered by increasing the TiO2 content. The Q x f values of nano-scaled alpha alumina could be tremendously boosted by adding an appropriate amount of TiO2. However, introducing excessive TiO2 into the alumina ceramics would instead lead to a decrease in the Q x f values. The phases of TiO2 and Al2TiO5 co-existed at 1350 degrees C, and the maximum Q x f value appeared right after the eradication of TiO2 phase at 1400 degrees C. Consequently, increasing the TiO2 content to 0.5 wt% yielded a Q x f value of 680 000 GHz (measured at 14 GHz) for nano-scaled alpha alumina prepared at 1400 degrees C for duration of 4 h. In addition, a very low loss tangent (tan delta) of 2 x 10(-5) was also obtained at 14 GHz. The tau(f) value is strongly correlated to the compositions and can be controlled through the existing phases. In fact, tau(f) could be adjusted to near zero by adding 8 wt% TiO2 to a alumina ceramics. A dielectric constant (epsilon(r)) of 10.81, a high Q x f value of 338 000 GHz (measured at 14 GHz), and a temperature coefficient of resonant frequency (tau(f)) of 1.3 ppm/degrees C were obtained for nano-scaled alpha alumina with 8 wt% TiO2 sintered at 1350 degrees C for 4 h. Sintered ceramic samples were also characterized by X-ray diffraction and scanning electron microscopy.