The effects of CuO addition on the microstructures and microwave dielectric properties of ZnTa2O6 ceramics were investigated. CuO was selected as a liquid-phase sintering aid to lower the sintering temperature of ZnTa2O6 ceramics. With CuO addition, the sintering temperature of ZnTa2O6 can be effectively reduced from 1350 to 1230 degreesC. The crystalline phase exhibited no phase difference and no second phase was detected at low addition levels (0.25-1 wt.%). The quality factors Q x f were strongly dependent upon the CuO concentration. A Q x f value of 65,500 GHz was obtained for specimen with 0.25 wt.% CuO addition at 1230 degreesC. For all levels of CuO concentration, the relative dielectric constants were not significantly different and ranged from 34.2 to 35.7. Tunable temperature coefficient of resonant frequency (tau(f)) can be adjusted to zero by appropriately turning the CuO content. (C) 2004 Elsevier Ltd. All rights reserved.