Study On Lifetime Characteristics And Influencing Factors On High Energy Density Ceramic Capacitors

The development of pulsed power technology requires a miniaturized and light power system. It is of great importance to increase the energy density of energy storage devices that occupy the largest proportion of volume and weight in the power system. Nowadays, capacitors are most widely used among all kinds of energy storage devices due to their comparatively reliable technology.BaTiO3 ceramic can be used as the dielectric material of the high energy density capacitor because of high dielectric constant, high voltage level, long lifetime and high inverse coefficients. The high energy density (700J/L) multilayer ceramic capacitors (MLC) of 1~10μF/500~1000V have been produced. This dissertation studies the temperature characteristic and the life characteristic of this kind of capacitor. Besides, it analyzes the breakdown mechanisms under DC and AC, and then proposes the fatigue breakdown model.This dissertation explains the high dielectric constant characteristic and high dielectric loss characteristic of BaTiO3 ceramic from the microcosmic structure. It also introduces the design principle of the test-bed which can do DC dielectric strength test and repeated charge-discharge tests. In the study of the temperature characteristic, the author finds that the capacitance of MLC keeps almost unchangeable for adding of peaking drifting substance and depressor. The dielectric loss angle tangent (tgδ) of MLC declines with the temperature rise, and this change is propitious for the long run of MLC under AC condition. The DC breakdown voltage declines with the temperature rise but it keeps high level in a wide rage of temperature.In the study of the life characteristic, it finds that the life declines oberviously with the increase of the charge voltage, the repeated frequency and the inverse coefficients. The MLC tends to have thermal breakdown when the temperature is too high, with a very shor life. The MLC tends to have fatigue breakdown when the temperature is lower. The process of fatigue breakdown includes the development of discharge channel. The inner stress and the temperature are the most important factors which determine the speed of flaw's extending. The inner stress'influence is greater than the temperature's.Finally, the whole researches are summarized, and the futher work is prospected.