Dielectric Properties and Nonohmic Behaviors of CaCu3Ti4O12 Ceramics Prepared by Sol-Gel Process

Abstract

A sol-gel process was used to synthesize gel precursor of CaCu3Ti4O12. The dry gel were calcined at 800℃/10h and 900℃/10h respectively, and then sintered in air at 1050℃ for 8h. The XRD patterns for calcined powder show that the second phases are contained, and the content of second phases for the powder calcined at 900℃ decreases drastically compared with the powder calcined at 800℃. However, all the second phases have disappeared after the sintering process for the pellets at the same conditions (1050℃/8h, air). The SEM results indicate that the existence of second phases is not conductive to the growth of grains and the formation of grain boundaries during the sintering process. The electric properties measurement demonstrates that the ceramics formulated from dry gel calcined at 900℃/h show not only larger permittivity values and lower dielectric loss, but also larger nonlinear coefficient values comparing those formulated from dry gel calcined at 800℃/h. The nonohmic behaviors measurement results suggest that the higher Schottky barrier is the main factor inducing the larger nonlinear coefficient.