Influence of V₂O₅ additions to Ba(Mg _1/3Ta_2/3)O₃ ceramics on sintering behavior and microwave dielectric properties

The microstructures and the microwave dielectric properties of barium magnesium tantalate ceramics prepared by conventional mixed oxide route have been investigated. The prepared Ba(Mg_1/3Ta_2/3)O ₃ exhibited a mixture of cubic perovskite and a hexagonal superstructure with Mg and Ta showing 1:2 order in the B-site. It is found that low level doping of V₂O₅ (up to 0.5wt.%) can significantly improve densification of the specimens and their microwave dielectric properties. The density of doped Ba(Mg_1/3Ta _2/3)O₃ ceramics can be increased beyond 95% of its theoretical value by 1500°C-sintering, which is caused by the liquid-phase effect of V₂O₅ addition. The detected second phase Ta ₂O₅ was mainly the result of V⁵⁺ substitution in the ceramics. Dielectric constant (ε_r) and temperature coefficient of resonant frequency (τ_f) were not significantly affected, while the unloaded quality factors Q were effectively promoted by V₂O₅ addition due to the increase in B-site ordering. The ε_r value of 24.1, Q × f value of 149,000 (at 10GHz) and τ_f value of 7.2ppm/°C were obtained for Ba(Mg _1/3Ta_2/3)O₃ ceramics with 0.25wt.% V ₂O₅ addition sintered at 1500°C for 3h.