New High‐Permittivity AgNb1‐xTaxO3 Microwave Ceramics: Part II, Dielectric Characteristics

Ceramic samples with the AgNb 1− x Ta x O 3 (0.46 < x < 0.54) composition were synthesized and analyzed, with respect to their dielectric properties, in a microwave‐frequency range and at radio frequencies. The permittivity over the compositional range 0.46 lessthan equal to x lessthan equal to 0.52 was >410, whereas the Q × f value, measured at 2 GHz, reaches values of 640–900 GHz. Dependence of the resonant frequency on temperature was not linear but did display a minimum at a particular temperature, which was dependent on the composition of the ceramic. Samples that were measured at radio frequencies displayed low dissipation factors ( tg δ= 7 ×10 −4 −18 × 10 −4 ), a low aging rate (0.2% per time decade), and good dielectric strength (8 V/μm at a thickness of 0.6 mm). Microstructural investigations revealed the presence of precipitates and transformation twins that should be eliminated during additional processing optimization.