Dielectric and Thermal Properties of Single-Crystalline CaCu3Ti4O12 at High Temperatures

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The dielectric and thermal properties of perovskite-related CaCu3Ti4O12 single crystals were studied at high temperatures. A dielectric anomaly was confirmed at $T_{1}=726$ K, while it was previously reported to be 732 K for ceramic samples. With increasing temperature, the dielectric constant $\varepsilon$ shows a shoulder-like round anomaly at around 600 K and a peak ($\varepsilon_{\text{peak}}\sim6.0\times 10^{5}$ at $ f=1$ MHz.) at $T_{1}$. CaCu3Ti4O12 exhibits an enormously high dielectric constant in both single crystals and ceramics even at high temperatures. Heat capacity was measured with an ac calorimeter, and the results also showed an anomaly around $T_{1}$. The present evidence indicates that CaCu3Ti4O12 undergoes a phase transition at $T_{1}$ in addition to the antiferromagnetic phase transition at 25 K.
2009-09-25