Abstract: Using Ca(NO₃)₂·4H₂O, Mg(NO₃)₂·6H₂O and Si(OC₂H ₅)₄ as precursors, (Ca_0.7Mg_0.3)SiO₃ powders were prepared by sol-gel method. The crystalline phase, microstructure, sintering characteristic and microwave dielectric properties of (Ca_0.7 Mg_0.3)SiO₃ powders calcined at different temperatures were studied. The results show that the powders calcined at 800℃ are almost amorphous and a large amount of crystalline phases are occurred when the calcination temperature increases to 900℃. The dielectric ceramics made from amorphous powders or fine powders (calcined at 900℃) can’t achieve compact structure, and the sintering characteristic and microwave dielectric properties can be enhanced by increasing the size of grains. Using (Ca_0.7 Mg_{0. 3})SiO₃ powders with grain sizes of 50--100nm and 90--300nm as raw materials, the ceramics sintered at 1320℃ possess good microwave dielectric properties: ε=6.62, Q× f=36962GHz, τ_f=-48.32×10^-6℃^-1 and ε=6.71, Q× f=41842GHz, τ_f=-49.63×10^-6℃^-1, respectively.

Key words: sol-gel, (Ca_0.7Mg_0.3)SiO₃, grain size, microwave dielectric properties