Influences of Al2O3/Nb2O5 co-doping on structural evolution and dielectric properties of Zn_(0.5)Ti_(0.5-x)(Al_(0.75)Nb_(0.35))xNbO4 (0 ≤ x ≤ 03) ceramics

摘要

In present study, the influences of Al2O3 and Nb2O5 co-doping for Ti site on structure and microwave dielectric performances of Zn_(0.5)Ti_(0.5-x)Al_(0.75)Nb_(0.35)NbO4 ceramics were discussed. Pure ixiolite-structured Zn_(0.5)Ti_(0.5)NbO4 solid solution is prepared when x ≤ 0.15. Phase transformation takes place at 0.2 ≤ x ≤ 0.3, where columbite ZnNb2O6 phase exists. The dielectric constant (εr) of ceramics presents a decline trend, which is attributed to the decrease of dielectric polarizability (0 ≤x ≤ 0.15) and the formation of ZnNb2O6 phase (0.2 ≤ x ≤ 0.3). The quality factor (Q×f), however, decrease till x = 0.15 and increase after that. The temperature coefficient of resonant frequency (τf) value varies consistently with the densification. Typical dielectric ceramics (x = 0.3) was synthesized at 1150°C: a εr of 25.79, a Q×f about 56114 GHz and a τf of-78.18 ppm/°C, were obtained.