Suppressed temperature dependence of the resonant frequency of a AgNb0.5Ta0.5O3 composite vs. single-phase ceramics

AgNb0.5Ta0.5O3 ceramics were synthesized and analyzed, with respect to their dielectric properties, in the radio- and microwave-frequency ranges. The influences of different synthesis conditions were investigated and correlated with the difficulties in preparing single-phase ceramics, as a consequence of the inhomogeneous distribution of Nb and Ta ions and the decomposition of the matrix phase. The results revealed that with the simple mixing of all three oxides and subsequent firing in air, it is possible to prepare composite material that is attractive for microwave applications due to inhomogeneity of the B-site cation distribution – a well-known issue that was in our case shown to be an advantage for decreasing the temperature dependence of the resonant frequency over a broad temperature range. On the other hand, we also succeeded in fabricating single-phase ceramics with a very high density through the initial formation of a precursor and sintering in an overpressure of oxygen.