Charge transfer in the high dielectric constant materials CaCu3Ti4O12 and CdCu3Ti4O12 -: art. no. 092106

The cubic perovskite-related ceramic CaCu3Ti4O12 has a very high static dielectric constant epsilon(0)greater than or similar to10 000 at room temperature (RT), which drops to about 100 below similar or equal to100 K. Substituting Cd for Ca reduces the RT value of epsilon(0) by over an order of magnitude. The origin of the large epsilon(0) is not fully understood, but may be due to an internal barrier layer capacitance (IBLC) effect. Infrared measurements on the Ca and Cd compounds show that low-frequency modes increase dramatically in strength at low temperature, suggesting a change in the effective charges and increasing electronic localization that may lead to a breakdown of the IBLC effect.