Microstructure and Microwave Dielectric Properties of TiO2-Doped Zn2SiO4 Ceramics Synthesized Through the Sol-Gel Process

(1-x)Zn2SiO4-xTiO(2) (x=0, 5, 8, 11, and 15 wt%) ceramics have been successfully prepared through a sol-gel process. The thermal gravimetry-differential thermal analysis and X-ray diffraction analysis showed that the addition of TiO2 can lower the nucleation temperature of Zn2SiO4 and enhance the sinterability of the powders synthesized. Dense ceramics with a pure phase could be achieved at a lower temperature. The pure Zn2SiO4 ceramics sintered at 1325 degrees C exhibited microwave dielectric properties: a dielectric constant (epsilon(r)) of 6.6, a quality factor Q x f of 198 400 GHz, and a temperature coefficient of resonant frequency (tau(f)) of -41.6 ppm/degrees C. The tau(f) value can be adjusted to near zero by adding an appropriate amount of TiO2. The Zn2SiO4 ceramics containing 11 wt% of TiO2 sintered at 1200 degrees C showed excellent microwave dielectric properties: an epsilon(r) value of 9.1, a Q x f value of 150 800 GHz, and a tau(f) value of -1.0 ppm/degrees C. Our results show that the sol-gel process can achieve pure phase as well as ultrafine powders, which is beneficial to optimize the performance of Zn2SiO4 ceramics. Zn2SiO4 ceramics containing 11 wt% of TiO2 are a promising candidate for microwave and millimeter-wave applications.