The sintering temperature of 0.95(Na0.5K0.5)NbO3-0.05BaTiO(3) (NKN-BT) ceramics needs to be decreased below 1000 degrees C to prevent Na2O evaporation, which can cause difficulties in poling and may eventually degrade their piezoelectric properties. NKN-BT ceramics containing CuO were well sintered at 950 degrees C with grain growth. Poling was easy for all specimens. Densification and grain growth were explained by the formation of a liquid phase. The addition of CuO improved the piezoelectric properties by increasing the grain size and density. High piezoelectric properties of d(33) = 230 pC/N, k(p) = 37%, and epsilon(T)(3)/epsilon(0)=1150 were obtained from the specimen containing 1.0 mol% of CuO synthesized by the conventional solid-state method.