Ceramics-Silikáty 54, (2) 103 - 107 (2010)

The sintering behavior, microstructure and microwave dielectric properties of BiNbO₄ ceramics sintered in N₂ with CuO and V₂O₅ additions were investigated. The CuO and V₂O₅ additives, acting as the sintering aids, could effectively lower the sintering temperature of BiNbO₄ ceramics. CuV₂O₆, formed by the reaction between CuO and V₂O₅ with the mole ratio of 1:1 at 500°C, was more effective to realize low-temperature sintering of BiNbO₄ ceramics than the CuO–V₂O₅ mixture. It was found that the addition of 0.1 wt% CuV₂O₆ to BiNbO₄ lowered the sintering temperature to approx 880°C while maintaining 98.4 % theoretical density. Pure orthorhombic BiNbO₄ phase was obtained successfully in the cases of CuO–V₂O₅ mixture or CuV₂O₆ additions. The CuO–V₂O₅ mixture addition would cause inhomogeneous and abnormal grain growth resulting in the degradation of densities and dielectric properties of BiNbO4 ceramics. By contrast, a uniform and dense microstructure was obtained in BiNbO₄ ceramics with CuV₂O₆-addition, contributed to higher dielectric constant and quality factor. The BiNbO₄ ceramics with 0.5 wt% CuV₂O₆ addition sintered at 860°C for 2 h have good microwave dielectric properties (at 4.3 GHz):relative dielectric constant (ε_r) = 47, quality factor (Q×f) = 11950 GHz.