A-site deficient perovskites Ba(M2+ 1/3Nb2/3)O3: microstructural attributes for a high quality factor

Slight A-site deficiency in ordered perovskites Ba(M2+ 1/3Nb2/3)O3(M - Co, Zn, Mg) is shown to promote the formation of single-phase dense ceramics, in which the microwave (MW) quality factor Q attains its maximum values. Any further decrease in the Ba concentration in Ba(M2+ 1/3Nb2/3)O3 always results in the formation of a multiphase material containing secondary phase with the tetragonal tungsten bronze (TTB) structure. The amount of TTB phase in the perovskite matrix was found to depend on both the Ba concentration and the sintering temperature. The composition and properties of the TTB phase are discussed in terms of their effect on the MW dielectric parameters of Ba(M2+ 1/3Nb2/3)O3 ceramics.