Effect of MgO excess on structure and microwave dielectric properties of Mg4Nb2O9 ceramics.

Corundum structured Mg₄Nb₂O₉ dielectric ceramics with the excess of MgO were prepared by the sol-gel process and microwave dielectric properties were investigated with the excess of MgO. First, according to the stoichiometric ratio of Mg₄Nb₂O₉ phase formation was studied by means of XRD analysis by adjusting the ratio of Mg/Nb and the ratio was ranging from 0·5 to 2·4. Subsequently, based on phase formation microwave dielectric properties of Mg₄Nb₂O₉ ceramics as a function of ratio of Mg/Nb were obtained depending on phase change. The results showed that when the ratio of Mg/Nb was 2·1, pure phase of Mg₄Nb₂O₉ ceramics could be obtained at 1275°C with excellent microwave dielectric properties of ε_r = 12·5, Qƒ = 224,000 GHz, τ_ƒ = −42·8 ppm/°C. [ABSTRACT FROM AUTHOR]