Low‐Temperature Sintering and Dielectric Properties of Ag(Nb,Ta)O 3 Composite Ceramics

The sintering behavior and dielectric properties of perovskite Ag(Nb 1− x Ta x )O 3 (0 < x < 1) solid solutions and two‐phase composite assemblages were explored. A small amount of CuO (1 wt%) was used for liquid‐phase sintering and led to high densification at temperatures <950°C. The temperature coefficient of capacitance, TCC, was adjusted by varying the Nb:Ta ratio within the solid‐solution series and by creating composite microstructures. Two‐phase assemblages consisting of Ag(Nb 3/4 Ta 1/4 )O 3 and Ag(Nb 1/4 Ta 3/4 )O 3 were synthesized to achieve a temperature‐stable dielectric material for high‐frequency applications. The composite dielectric with CuO addition had an average dielectric constant of 390 and a Q × f factor of 410 GHz at 2 GHz, with a stable TCC (0 to −180 ppm/°C) in the temperature range from −20° to +60°C. In addition, process compatibility with a silver conductor was confirmed by high‐frequency ring‐resonator measurements and microstructural characterization. The Ag(Nb 1− x Ta x )O 3 solid solutions and composites are promising candidates as embedded capacitors for radio‐frequency/microwave applications.