Intrinsic limit of dielectric loss in several Ba(B 1/3B 2/3)O3 ceramics revealed by the whispering-gallery mode technique

Whispering-gallery mode spectroscopy is employed to study the dielectric permittivity and losses of Ba(Mg1/3Ta2/3)O3, Ba(Mg1/3Nb2/3)O3, and Ba(Co1/3Nb2/3)O3 ceramics in the frequency range of 40-90 GHz and temperature interval of 5-295 K. Below 50 GHz, the room-temperature extrinsic dielectric losses in Ba(Mg1/3Ta2/3)O3 and Ba(Mg1/3Nb2/3)O3 manifest themselves as a sublinear loss factor tand dependence until the intrinsic losses start to dominate the spectra around 50-70 GHz. Based on these data we obtain the room-temperature intrinsic limit of dielectric loss of Ba(Mg1/3Ta2/3)O3 (Qxf =430+-20 THz) and of Ba(Mg1/3Nb2/3)O3 (Qxf =230+-20 THz). In the case of Ba(Co1/3Nb2/3)O3, the extrinsic losses were predominant throughout the studied frequency range. The possible sources of this loss are discussed.