Structure and electrical response of CaCu3Ti4O12 ceramics: Effect of heat treatments at the high vacuum

In this work, CaCu3Ti4O12 (CCTO) ceramics based perovskite varistors were prepared using the solid-state reaction method, and effects of heat treatments at the high vacuum on their microstructures and electrical properties were investigated experimentally. Two conditions of heat treatment, i.e., calcining at 950 °C for 10 h and then sintering at 1100 °C for 20 h, and at 900 °C for 2 h in 10−4 Pa vacuum level were used. It was found from the X-ray diffraction (XRD) that for the former condition, the single phase of CCTO based on the perovskite structure was formed, whereas for the later condition, multiple phases were detected due to the decomposing of CCTO. The electrical response of both conditions was monitored using the dielectric spectroscopy and was revealed that varistor voltage increased remarkably due to the heat treatments at the high vacuum.