Tetragonal Tungsten Bronzes in Ba(M2+1/3Nb2/3)O3Microwave Ceramics

For the first time, the dielectric properties of the 9:1:7 TTB phases Ba9M2+Nb14O45 (M = Co, Mg, Zn) which form in Ba-deficient high-Q perovskite niobates Ba(M2+ 1/3Nb2/3)O3 have been measured in the radio-frequency and microwave range. The low-temperature dielectric relaxation found in Ba9M2+Nb14O45 was shown to give a strong contribution into their microwave dielectric loss. The measured data were used for a simple simulation of the Q-factor of a perovskite-TTB composite. Calculated parameters have been shown to correspond well to the measured data.