Improved microwave dielectric properties of B_2O_3-doped Nd(Co_(1/2)Ti_(1/2))O_3 ceramics with near zero temperature coefficient of resonant frequency

摘要

The microwave dielectric properties and the microstructures of Nd(Co_(1/2)Ti_(1/2))O_3 ceramics prepared by conventional solid-state route have been studied. The prepared Nd(Co_(1/2)Ti_(1/2))O_3 exhibited a mixture of Co and Ti showing 1:1 order in the B-site. It is found that low-level doping of B_2O_3 (up to 0.75 wt.%) can significantly improve the density and dielectric properties of Nd(Co_(1/2)Ti_(1/2))O_3 ceramics. Nd(Co_(1/2)Ti_(1/2))O_3 ceramics with additives could be sintered to a theoretical density higher than 98.5% at 1320℃. Second phases were not observed at the level of 0.25-0.75 wt. % B_2O_3 addition. The temperature coefficient of resonant frequency (τ_f) was not significantly affected, while the dielectric constants (ε_r) and the unloaded quality factors Q were effectively promoted by B_2O_3 addition. At 1320℃/4 h, Nd(Co_(1/2)Ti_(1/2))O_3 ceramics with 0.75 wt.% B_2O_3 addition possesses a dielectric constant (ε_r) of 27.2, a Q x f value of 153,000 GHz (at 9 GHz) and a temperature coefficient of resonant frequency (τ_f) of 0 ppm/℃. The B_2O_3-doped Nd(Co_(1/2)Ti_(1/2))O_3 ceramics can find applications in microwave devices requiring low sintering temperature.