Microwave Dielectric Properties of Textured BaLa4Ti4O15 Ceramics with Layered Perovskite Structure

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Textured ceramics of BaLa4Ti4O15 (BaLT) with layered perovskite structure have been investigated by characterizing their dielectric properties at MHz and GHz frequencies. The highly grain-oriented ceramics were obtained by a templated grain growth technique. Hexagonal {001}-platelet BaLT particles prepared in molten salt were used as the template. The sintered ceramics containing template powders of 10 wt % exhibited a degree of $\langle 001\rangle$-orientation of 80% for the casting plane, whereas the plane perpendicular to the casting direction showed a degree of $\langle hk0\rangle$-orientation of 76%. The effect of grain orientation on the dielectric properties was observed as an anisotropy between the directions of parallel and perpendicular to the $c$-axis. As a result of the anisotropy, enhanced microwave dielectric properties ($\varepsilon_{\text{r}}=53$, $Q\cdot f=41{,}400$ GHz and $\tau_{\text{f}}=-1$ ppm/°C) compared with those of a randomly oriented ceramics were obtained in the TE011 mode for a cylindrical specimen with a {001} grain-orientation in the circular plane.
2005-09-15