Abstract
CaCu3–xZnxTi4O12 (x is from 0 to 1·0) polycrystalline samples were fabricated via a two-step solid state reaction process. The lattice parameter of the monophasic CaCu3Ti4O12 phase increased as Zn content increased. Scanning electron microscopy (SEM) images of the CCTO ceramic show bimodal grain size distribution and the grain size decrease largely with the appearance of Zn2TiO4 second phase. The dielectric permittivity of pure CCTO ceramic is ∼1·5×104 at f = 100 Hz. The dielectric constant of the sample largely increased with Zn substitution in the frequency range f<104 Hz. The highest dielectric constant was 6·2×104 at f = 100 Hz with Zn substitution of x = 0·8. The improved dielectric properties are believed to be related to the presence of a thin grain boundary barrier layer. The resistivity of the grain boundary decreased largely with Zn substitution as evidenced from the impedance plots.
Acknowledgements
Financial support of this research by the National Science Council, Taiwan, under the grant no. NSC 98-2221-E-036-012 is gratefully acknowledged.