Investigation on the decomposable process and the secondary liquid phase effect on the dielectric properties of CaCu3Ti4O12 ceramics

Abstract

CaCu3Ti4O12 (CCTO) single-phase powder synthesized by the solid-state reaction method was used to investigate the decomposition reaction after different sintering conditions, in which copper (Cu) atoms played a key role. A secondary intergranular liquid phase (Cu-rich, especially CuO-rich), which is related to both the abnormal grain and the domain boundary growths, started to appear at the grain boundaries when the CCTO pellet was sintered at 1000 °C. The liquid phase improved the dielectric properties of the 1000 °C sample, such as dielectric constant as high as 17 000 and dielectric loss as low as 0.074 at the measured frequency of 1 kHz. Meanwhile, the CuO-rich phase existed only on the surface layers and disappeared from the surface of the pellets sintered at 1100 °C for 10 h. The grain size increased significantly with the sintering temperature. The liquid phase also played an important role in the microstructure evolution and in the improvement of the dielectric properties. In addition, CCTO completely decomposed when sintered for 10 h at temperatures higher than 1100 °C.