Structure, far-infrared reflectance spectra, and microwave dielectric properties of Ba2MGa11O20 (M = Bi, La) ceramics

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 degrees C for 6 h has the best microwave dielectric properties with low epsilon(r) = 10.68, Q x f = 41,756 GHz, and negative tau(f) = 61.3 ppm/degrees C. BLG ceramic sintered at 1440 degrees C for 6 h exhibits epsilon(r) = 13.94, Q x f = 45,592 GHz, and near-zero tau(f) = 16.3 ppm/degrees C. The large deviation between epsilon(r) and epsilon(th) was ascribed to the rattling effect of the cations and the existence of lone pair ions of Bi3+. The difference in Q x f of the two ceramics was discussed in terms of packing fraction, and the tf of BLG was closer to zero than that of BBG due to the smaller tau(epsilon) value. Their intrinsic dielectric properties were analyzed through far-infrared reflectivity spectroscopy.

Automated summary

Ba2MGa11O20 ceramics (BBG and BLG) with monoclinic space group I2/m were prepared and exhibited good microwave dielectric properties at different sintering temperatures. BBG ceramic showed low dielectric constant and negative temperature coefficient, while BLG ceramic had higher dielectric constant and temperature coefficient closer to zero.