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A. Belous and O. Ovchar

Abstract

Several types of multiphase ceramic materials with excellent microwave (MW) dielectric properties have been considered. Studied materials were based on complex niobates and titanates with various crystal structures in which very high values of the MW quality factors (Q) can be attained. Slight compositional changes in the complex oxide systems have been shown to induce rather combined effect on the cation arrangement of separate crystal phases as well as on the microstructure and phase composition of multiphase ceramic materials. As a consequence, the ways to tailor MW dielectric parameters of the ceramics through a proper adjustment of both structure and distribution of enclosed phases have been presented and discussed. The examples of the multiphase MW dielectrics with enhanced properties have also been presented.

Open access

O. Ovchar, D. Durylin, A. Belous, B. Jancar and Kolodiazhnyi

Abstract

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.