Effect of B2O3 Additives on Sintering and Microwave Dielectric Behaviors of CuO-Doped ZnNb2O6 Ceramics

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The influences of B2O3 additives on the sintering behavior and microwave dielectric properties of CuO-doped ZnNb2O6 ceramics were investigated. The B2O3 and CuO additives effectively lowered the sintering temperature of ZnNb2O6 ceramics to below 800°C. The sintering temperature of CuO-doped ZnNb2O6 decreased with increasing B2O3 content. Dielectric constant $\varepsilon_{r}$ was not significantly changed and increased slightly with increasing B2O3 content, while the unloaded $Q$ value was affected by the additives. The $Q\times f$ value was found to be a function of both the sintering temperature and the amount of additives. With 5 wt% CuO and 4 wt% B2O3 additions, the $Q\times f$ value varied from 24000 to 46800 GHz as the sintering temperature increased from 780°C to 900°C for 2 h. The $\tau_{f}$ value increased in positive values with B2O3 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 $\varepsilon_{r}\sim 23.3$, $Q\times f\sim 46800$ GHz and $\tau_{f}\sim -6.7$ ppm/°C can be obtained for doped ZnNb2O6 ceramics sintered at 900°C for 2 h.
2002-02-15