Processing influence in the CaCu3Ti4O12 electrical properties

Abstract

CaCu3Ti4O12 (CCTO) is a complex oxide with a perovskite structure that is widely studied due to its dielectric and non-ohmic properties. The formation and composition of grains and grain boundaries are very important factors to improve these electrical properties. In this work, CCTO-based ceramics were processed by solid-state reaction at different calcination temperatures (700 °C to 1000 °C, for 4 h) and sintering at 1100 °C for 6 h aiming optimization in capacitor–varistor properties. The changes in crystal phase composition observed via XRD and chemical contrasts visualized by SEM/EDS point out that the disappearance of the secondary CuO phase of calcined powders is linked to complete Cu ion incorporation to the crystal structure of CCTO. This phenomenon culminated in sinterization via liquid phase formation, with abnormal grain growth for samples calcined at temperatures higher than 900 °C. The calcination occurring at 800 °C for 4 h, to produce CCTO with a more homogeneous microstructure, with apparent porosity of 2.67%, α of 5.49, EB of 1505 V cm−1, e′ (1 kHz) of 7506 and ΦB of 0.754 eV, was considered the best processing condition.