Low-Temperature Sintering and Dielectric Properties of Ag(Nb,Ta)O_3 Composite Ceramics

摘要

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℃. 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 x f factor of 410 GHz at 2 GHz, with a stable TCC (0 to -180 ppm/℃) in the temperature range from -20° to +60℃. 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.