The effects of CuO additive on the microstructures, the phase formation and the microwave dielectric properties of MgTiO3-CaTiO3 ceramics were investigated. The sintering temperature of CuO-doped 0.95MgTiO(3)-0.05CaTiO(3) (95MCT) ceramics can be lowered to 1275 degreesC due to the liquid phase effect. The microwave dielectric properties are found strongly correlate with the sintering temperature as well as the amount of CuO addition. At 1275 degreesC, 0.95MgTiO(3)-0.05CaTiO(3) ceramics with 0.25 wt.% CuO addition possesses a dielectric constant epsilon(r) of 20, a Q x f value of 51 000 (at 7 GHz) and a tau (f) value of -8.3 ppm degreesC(-1). By appropriately adjusting the x value in the (1 - x)MgTiO3-xCaTiO(3) ceramic system, zero tau (f) value can be obtained. (C) 2002 Elsevier Science B.V. All rights reserved.