Nonintrinsic origin of the colossal dielectric constants in Ca Cu 3 Ti 4 O 12

The dielectric properties of $\mathrm{Ca}{\mathrm{Cu}}_{3}{\mathrm{Ti}}_{4}{\mathrm{O}}_{12}$, a material showing colossal values of the dielectric constant, were investigated over a broad temperature and frequency range extending up to $1.3\phantom{\rule{0.3em}{0ex}}\mathrm{GHz}$. A detailed equivalent-circuit analysis of the results and two crucial experiments, employing different types of contacts and varying the sample thickness were performed. The results provide clear evidence that the apparently high values of the dielectric constant in $\mathrm{Ca}{\mathrm{Cu}}_{3}{\mathrm{Ti}}_{4}{\mathrm{O}}_{12}$ are nonintrinsic and due to electrode polarization effects. The intrinsic properties of…