The effect of CuO addition on the microstructures and the microwave dielectric properties of (Zr0.8Sn0.2)TiO4 ceramics have been investigated. It is found that low-level doping of ZnO (1 wt%) and CuO (up to 2 wt%) can significantly improve the density and dielectric properties of (Zr0.8Sn0.2)TiO4 ceramics. (Zr0.8Sn0.2)TiO4 ceramics with additives could be sintered to a theoretical density higher than 96% at 1220 degreesC, due to the liquid phase effect of CuO addition, as observed by scanning electron microscopy (SEM). A secondary phase was not observed at the level of 0.5-2 wt% CuO addition. The dielectric constant (epsilon (r)). While the temperature coefficient of resonant frequency ( if) were not significantly affected, the unloaded quality factors Q were effectively promoted by CuO addition. An epsilon (r) value of 38, Q.f value of 50000 (at 7 GHz), and tau (f) value of 3 ppm/degreesC were obtained for 1 wt% ZnO doped (Zr0.8Sn0.2)TiO4 ceramics with 1 wt% CuO addition sintered at 1220 degreesC. (C) 2000 Elsevier Science Ltd. All rights reserved.