The effect of CuO addition on the microstructures and the microwave dielectric properties of MgTa2O6 ceramics has been investigated. It is found that low level-doping of CuO (up to 1 wt.%) can significantly improve the density of the specimens and their microwave dielectric properties. Tremendous sintering temperature reduction can be achieved due to the liquid phase effect of CuO addition observed by scanning electronic microscopy (SEM). The sintered samples exhibit excellent microwave dielectric properties, which depend upon the liquid phase and the sintering temperature. With 0.5 wt.% CuO addition, MgTa2O6 ceramic can be sintered at 1400degreesC and possesses a dielectric constant (epsilon(r)) of 28, a Q x f value of 58000 GHz and a temperature coefficient of resonant frequency (tau(f)) of 18 ppm/degreesC. (C) 2004 Elsevier B.V. All rights reserved.