Dielectric Properties of a New Ceramic System (Mg0.95Zn0.05)2TiO4–CaTiO3 at Microwave Frequencies

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The microwave dielectric properties and microstructure of a two-phase (Mg0.95Zn0.05)2TiO4–CaTiO3 ceramic system prepared using the conventional solid-state route were investigated. The structure and microstructure were analyzed by X-ray diffraction and scanning electron microscopy, respectively. Ilmenite-structured (Mg0.95Zn0.05)TiO3 was detected as a second phase. The coexistence of the second phase, however, did not degrade the dielectric properties of the specimen because the phases were compatible. At 1270 °C, 0.92(Mg0.95Zn0.05)2TiO4–0.08CaTiO3 ceramic showed a good combination of microwave dielectric properties: a dielectric constant ($\varepsilon_{\text{r}}$) of ${\sim}18.03$, a quality factor ($Q \times f$) value of ${\sim}153{,}000$ GHz (at 10 GHz), and a temperature coefficient of resonant frequency ($\tau_{\text{f}}$) of ${\sim} {-16.82}$ ppm/°C. The $\tau_{\text{f}}$ value is strongly correlated to the composition and can be controlled by the compositional ratio. At $x = 0.1$, an $\varepsilon_{\text{r}}$ of ${\sim}19.15$, a $Q \times f$ value of ${\sim}94{,}400$ GHz (at 10 GHz), and a $\tau_{\text{f}}$ of ${\sim}1.5$ ppm/°C were obtained for 0.9(Mg0.95Zn0.05)2TiO4–0.1CaTiO3 ceramic sintered at 1270 °C for 4 h.
2009-07-25