Mechanism of Capacitance Aging under DC Electric Fields in Multilayer Ceramic Capacitors with X7R Characteristics

摘要

Capacitance aging under DC electric fields has been studied on multilayer ceramic capacitors (MLCCs) with X7R characteristics. The capacitance change with time was divided into two consecutive stages. The first stage was due to the nonlinear permittivity of dielectrics and it should not be involved in the aging phenomenon. The second stage depended on the MnO content, grain size and firing conditions of the dielectrics. The aging was markedly depressed above the Curie temperature. From the behavior of the second stage, it was concluded that the capacitance aging is caused by the 90° domain switching in BaTiO_3 in the core. An equation that represents the aging behavior in the second stage was presented and the mechanism that explains the capacitance aging was proposed. The first stage was due to the nonlinear permittivity and the second stage was due to the domain switching, but the domain switching was also included in the first stage if the domain walls were moved by the first application of a DC field. The change in the aging behavior with the intensity of the DC field could be explained by separating capacitance change into that due to the nonlinear permittivity and that due to the domain switching according to the mechanism proposed in this study. Finally, a methodology for handling the capacitance aging under DC fields was proposed.