Origin of ferroelectric-like hysteresis loop of CaCu3Ti4O12 ceramic studied by impedance and micro-Raman spectroscopy

TL;DR

This study investigates the origin of ferroelectric-like hysteresis in CaCu3Ti4O12 ceramics, revealing it stems from grain boundary charges rather than Ti ion displacement, with micro-Raman and impedance analyses supporting this.

Contribution

It demonstrates that the ferroelectric-like behavior in CCTO ceramics is caused by grain boundary charges, not Ti ion displacement, providing new insight into their electrical properties.

Findings

Hysteresis loops are due to grain boundary charges, not Ti displacement.

Impedance spectrum shows a relaxation time of 2.9 ms linked to grain boundary charges.

Micro-Raman mapping identifies CuO layers at grain boundaries.

Abstract

Ferroelectric-like hysteresis loops of CaCu3Ti4O12 (CCTO) ceramic have been observed. We found that this unusual feature does not arise from the displacement of the Ti ions in the TiO6 octahedron, but apparently comes from the charges at the grain boundaries which consist of a CuO layer. The relaxation time of 2.9 milliseconds by the charges from the grain boundary, nearly corresponding to the inverse P - V sampling frequency of 1kHz, has been found in the impedance spectrum. According to the micro-Raman mapping, the CuO layer is found in the grain boundary and is perfectly distinguished from the CCTO grain.