Intrinsic limit of dielectric loss in several Ba(B1∕3′B2∕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 40–90GHz and temperature interval of 5–295K. Below 50GHz, 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 tanδ(ω) dependence until the intrinsic losses start to dominate the spectra around 50–70GHz. Based on these data we obtain the room-temperature intrinsic limit of dielectric loss of Ba(Mg1∕3Ta2∕3)O3 (Q×f=430±20THz) and of Ba(Mg1∕3Nb2∕3)O3 (Q×f=230±20THz). 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.