Effects of Glass Addition on Microwave Dielectric Properties of Zn0.95Mg0.05TiO3 + 0.25TiO2 Ceramics

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The effects of Bi2O3 addition on the microwave dielectric properties and the microstructures of Zn0.95Mg0.05TiO3 + 0.25TiO2 with 1 wt% 3ZnO–B2O3 (ZnBO–ZMT$'$) ceramics prepared by conventional solid-state routes have been investigated. In a preliminary study, it was shown that ZnBO–ZMT$'$ ceramics can be sintered to a theoretical density higher than 95% at 900°C. In this study, the effects of Bi2O3 additions of up to 10 wt% on the sintering characteristics of the ZnBO–ZMT$'$ ceramics was investigated at the sintering temperatures ranging from 860 to 960°C. Sintered ceramic samples were characterized by X-ray diffraction and scanning electron microscopy (SEM). It was found that as the content of Bi2O3 increases, the density of the sintered ceramics increases, and the sintering temperature can be lowered to 880°C by adding 5 wt% Bi2O3. The ZnBO–ZMT$'$ ceramic with 5 wt% Bi2O3 addition sintered at 880°C exhibits the optimum dielectric properties: $Q\times f=4000$ GHz, $\varepsilon_{\text{r}}=24.6$, and $\tau_{\text{f}}=-14$ ppm/°C. Unlike the ZnBO–ZMT$'$ ceramic without Bi2O3 addition sintered at above 920°C, the ceramics with Bi2O3 additions show no Zn2TiO4 existence at 960°C sintering. It is therefore demonstrated that the addition of Bi2O3 can suppress the formation of Zn2TiO4 in ZnBO–ZMT$'$ ceramics.
2005-04-15