Improvement of microwave dielectric properties of Ba_2Ti_9O_(20) ceramics using [Zn_(1/3)Nb_(2/3)]~(4+) substitution for Ti~(4+)

摘要

Ba_2[Zn_(1/3)Nb_(2/3)]_xTi_(9_x)O_(20) (x = 0-0.5) ceramics with high-quality factors were successfully prepared via traditional solid-state method. In this work, the microstructure and microwave dielectric properties of the samples were studied. The X-ray diffraction patterns indicated that two different phases BaTi_4O_9 and Ba_2Ti_9O_(20) existed at x = 0, while the phase of Ba_2Ti_9O_(20) was found gradually dominating in specimens with the doping of [Zn_(1/3)Nb_(2/3)]~(4+). At the level of x = 0.5, a fraction of the monoclinic phases of Ba_2Ti_9O_(20) were transformed into the triclinic phase. Furthermore, the SEM and relative density were used to confirm the homogeneous microstructure of the Ba_2[Zn_(1/3)Nb_(2/3)]_xTi_(9-x)O_(20) ceramics. The doping of [Zn_(1/3)Nb_(2/3)]~(4+) can effectively improve the microwave properties of Ba_2Ti_9O_(20) ceramics, which are shown as the increase of dielectric constant, quality factor, and the stability of temperature coefficient. Particularly, the excellent microwave dielectric properties were achieved for the Ba_2[Zn_(1/3)Nb_(2/3)]_(0.3)Ti_(8.7)O_(20) ceramics sintered at 1300 °C, with ε_r～39.3, a high Q×f～43,879 at 6 GHz, and a τ_f～+7 ppm/°C.