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

Using Ca(NO3)(2)center dot 4H(2)O, Mg(NO3)(2)center dot 6H(2)O, Si(OC2H5)(4), LiNO3 and Bi(NO3)(3)center dot 5H(2)O 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 U-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 degrees C and 800 degrees C, respectively. The sintering characteristic and dielectric properties of powders calcined at 750 degrees C with different content of powders calcined at 800 degrees C were studied. When the content of powders calcined at 800 degrees C was 10 wt%, the dielectric ceramic sintered at 890 degrees C had compact structure, and possessed excellent microwave dielectric properties: epsilon(r) = 7.16, Q x f = 25630 GHz, tau(f) = -69.26 ppm/degrees C. (C) 2008 Elsevier Ltd. All rights reserved.