Grain boundary segregation and microwave dielectric properties of low loss Mg _1·5 Zn _0·5 SiO ₄ ceramics containing Bi ₂ O ₃

Uncommon low loss Mg1·5Zn0·5SiO4 ceramics containing Bi2O3 were investigated by focusing on the roles of Bi2O3 on phase evolution and resultant microwave dielectric properties. While the primary goal of lowering sintering temperature can be easily assumed, some unexpected behaviours of the Bi2O3 containing materials are highlighted with experimental evidences concerning selective dissolution of Zn2SiO4 and grain boundary segregation of gradual Bi richer phases. These evidences are strongly dependent on the content of Bi2O3 and sintering temperature. As an optimal composition, Mg1·5Zn0·5SiO4 with 0·5 mol.-%Bi2O3 exhibited promising dielectric properties of a k value ∼6·8 and a Q×f value ∼23 300 at a sintering temperature of 1150°C, which is much lower than typical sintering temperature of 1450°C.