Synthesis and microwave dielectric properties of CaO–MgO–SiO2 submicron powders doped with Li2O–Bi2O3 by sol–gel method

Using Ca(NO3)2·4H2O, Mg(NO3)2·6H2O, Si(OC2H5)4, LiNO3 and Bi(NO3)3·5H2O as raw materials, CaO–MgO–SiO2 submicron powders were prepared at low temperature by sol–gel method. The crystallization temperature was decreased enormously by the introduction of Li–Bi liquid phase sintering aids into Ca–Mg–Si sol, and the powders with average particle sizes of 80–100 nm and 200–400 nm were obtained at the calcining temperature of 750 °C and 800 °C, respectively. The sintering characteristic and dielectric properties of powders calcined at 750 °C with different content of powders calcined at 800 °C were studied. When the content of powders calcined at 800 °C was 10 wt%, the dielectric ceramic sintered at 890 °C had compact structure, and possessed excellent microwave dielectric properties: ɛr = 7.16, Q × f = 25630 GHz, τf = −69.26 ppm/°C.