In this paper, the microwave dielectric behavior of ZnNb2O6-TiO2 ceramics synthesized at different conditions was studied. ZnNb2O6-1.75TiO(2) ceramics, sintered at 1050 degrees C, exhibited a good dielectric behavior. CuO and B2O3 were used as sintering aids to decrease the sintering temperature of the above materials. According to XRD analysis, the reaction between columbite ZnNb2O6 and rutile occurred, resulted in new phase ZnTiNb2O8 and Zn0.17Nb0.33Ti0.5O2. The change of crystal grain and densification was also observed with SEM. Results indicated that the dielectric behavior of samples strongly depended on structural transitions and microstructure of materials. We found that 2.0 wt.% CuO doped ZnNb2O6-1.75TiO(2) ceramics with 2.0 wt.% B2O3 additive sintered at 975 degrees C exhibited good dielectric properties: epsilon(r) = 40, Q x f = 17,000 GHz (at 5.6 GHz) and tau(f) = -12 ppm degrees C-1. The high specific insulation resistance and excellent compatibility with Ag90Pd10 electrode suggested that ZnNb2O6-1.75TiO(2) ceramics was suitable for manufacturing multilayer ceramic capacitors with a high reliability. (C) 2009 Elsevier B.V. All rights reserved.