Charge transfer in the high dielectric constant materials CaCu3Ti4O12 and CdCu3Ti4O12

TL;DR

This paper investigates charge transfer mechanisms in high dielectric constant materials CaCu3Ti4O12 and CdCu3Ti4O12, revealing temperature-dependent dielectric behavior and the impact of substitution on their electrical properties.

Contribution

It provides new insights into the charge transfer processes and dielectric behavior in these complex oxides, highlighting the role of internal barrier layer capacitance and temperature effects.

Findings

High dielectric constant (~10000) at room temperature for CaCu3Ti4O12

Dielectric constant drops significantly below 100 K

Substituting Cd reduces the dielectric constant by over an order of magnitude

Abstract

The cubic perovskite-related ceramic CaCu3Ti4O12 has a very high static dielectric constant ~10000 at room temperature (RT), which drops to about 100 below about 100 K. Substituting Cd for Ca reduces the RT value of the dielectric constant by over an order of magnitude. The large the dielectric constant may be due to an internal barrier layer capacitance (IBLC) effect. Infrared optical properties show a low-frequency mode that increases dramatically in strength at low temperature, suggesting a change in the effective charges and a breakdown of the IBLC model due to a semiconductor-to-insulator transition.