Effect of B2O3Additives on Sintering and Microwave Dielectric Behaviors of CuO-Doped ZnNb2O6Ceramics

The influences of B 2 O 3 additives on the sintering behavior and microwave dielectric properties of CuO-doped ZnNb 2 O 6 ceramics were investigated. The B 2 O 3 and CuO additives effectively lowered the sintering temperature of ZnNb 2 O 6 ceramics to below 800°C. The sintering temperature of CuO-doped ZnNb 2 O 6 decreased with increasing B 2 O 3 content. Dielectric constant ε r was not significantly changed and increased slightly with increasing B 2 O 3 content, while the unloaded Q value was affected by the additives. The Q × f value was found to be a function of both the sintering temperature and the amount of additives. With 5 wt% CuO and 4 wt% B 2 O 3 additions, the Q × f value varied from 24000 to 46800 GHz as the sintering temperature increased from 780°C to 900°C for 2 h. The τ f value increased in positive values with B 2 O 3 doped, while decreased in negative values with CuO addition. Zero temperature coefficient of the resonant frequency can be achieved by properly adjusting the concentration of additives. For low-firing multilayer applications, dielectric properties of ε r ∼23.3, Q × f ∼46800 GHz and τ f ∼-6.7 ppm/°C can be obtained for doped ZnNb 2 O 6 ceramics sintered at 900°C for 2 h.