The effect of CuO additions on the firing temperature of ZnNb2O6 ceramics was investigated using dilatometry, transmission electron microscopy, and X-ray diffractometry, A 5 wt% CuO addition to ZnNb2O6 ceramics significantly lowered the firing temperature from 1150 degrees to similar to 900 degreesC. The presence of a CuO-rich intergranular phase in the specimen was observed and was evidence of the formation of a liquid phase during sintering, The composition of the liquid phase was (ZnCu2)Nb2O8. In particular, the low-fired ZnNb2O6 ceramics had good microwave dielectric characteristics-Q x f = 59 500, epsilon (r) = 22.1, tau (r) = -66 ppm/degreesC. These properties were correlated with the formation of a second phase, (ZnCu2)Nb2O8.