Extrinsic models for the dielectric response of CaCu{3}Ti{4}O{12}

TL;DR

This paper models the dielectric response of CaCu3Ti4O12 by considering inhomogeneities at domain boundaries, providing expressions for six possible morphologies that explain its large, temperature-independent dielectric constant.

Contribution

It introduces a decision tree approach to model various boundary morphologies and derives dielectric expressions for each, explaining the observed dielectric behavior.

Findings

All six boundary morphologies can produce observed dielectric constants.

The models suggest inhomogeneities are key to the dielectric response.

Further experiments are proposed to identify the actual boundary types.

Abstract

The large, temperature-independent, low-frequency dielectric constant recently observed in single-crystal CaCu{3}Ti{4}O{12} is most plausibly interpreted as arising from spatial inhomogenities of its local dielectric response. Probable sources of inhomogeneity are the various domain boundaries endemic in such materials: twin, Ca-ordering, and antiphase boundaries. The material in and neighboring such boundaries can be insulating or conducting. We construct a decision tree for the resulting six possible morphologies, and derive or present expressions for the dielectric constant for models of each morphology. We conclude that all six morphologies can yield dielectric behavior consistent with observations and suggest further experiments to distinguish among them.