Microwave dielectric properties of (1 − x)SiO2–xTiO2 composite ceramics derived from core–shell structured microspheres

By using a sol–gel process under solvothermal conditions (SGS), the (1 − x)SiO2–xTiO2 (0.1 ≤ x ≤ 0.3) composite powders with a core–shell structure were prepared and its microwave dielectric properties were investigated for the first time. The 0.85SiO2–0.15TiO2 ceramics sintered at 1200 °C possess excellent microwave dielectric properties of ɛr ∼ 5.4, Q·f ∼ 40,500 GHz and τf near to 0 ppm/°C. The optimum sintering temperature was reduced 475 °C compared to that by a conventional solid-state method.