LAUSR

Abstract Ba2MGa11O20 (M = Bi, La; called BBG and BLG, respectively) ceramics with monoclinic space group I2/m were prepared through a solid-state reaction method. BBG ceramic sintered at 1150 °C for 6 h has the best microwave dielectric properties with low er = 10.68, Q × f = 41,756 GHz, and negative τf = −61.3 ppm/°C. BLG ceramic sintered at 1440 °C for 6 h exhibits er = 13.94, Q × f = 45,592 GHz, and near-zero τf = −16.3 ppm/°C. The large deviation between er and eth was ascribed to the “rattling” effect of the cations and the existence of lone pair ions of Bi3+. The difference in Q × f of the two ceramics was discussed in terms of packing fraction, and the τf of BLG was closer to zero than that of BBG due to the smaller τe value. Their intrinsic dielectric properties were analyzed through far-infrared reflectivity spectroscopy.