Microwave Dielectric Properties of Ba4.2(Sm0.8Nd0.17Bi0.03)9.2Ti18O54 Solid Solution with TiO2 Added

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The effects of TiO2 addition on the microwave dielectric properties of Ba6-3x(Sm1-y-zNdyBiz)8+2xTi18O54 (BSNBT) ceramics, with $x=0.6$, $y=0.17$, and $z=0.03$, have been investigated. The microstructure of BSNBT doped with TiO2 was analyzed using X-ray diffraction (XRD) analysis, electron probe microanalysis (EPMA) and field-emission scanning electron microscopy (FE-SEM). XRD and EPMA analysis reveals the existence of second phases. The addition of small amounts of TiO2 ($\leq 1.0$ wt %) increased $Q\cdot f$ markedly and improved $\mathrm{TC} f$ without any influence on dielectric constant ($\varepsilon_{\text{r}}$). However, the addition of excess TiO2 reduced the bulk density and dielectric properties of the materials. BSNBT doped with 0.5 wt % TiO2 exhibited excellent dielectric properties with $\varepsilon_{\text{r}}=80.5$, $Q\cdot f=9009$ GHz and $\mathrm{TC} f=6.5$ ppm/°C when sintered at 1340 °C for 2 h. The reasons for the nonlinear behavior of $\mathrm{TC} f$ are also provided.
2006-08-15