Investigation on the piezo-ceramic discoloration during the DC electrical degradation process

The electrical degradation of piezoelectric ceramics occurs during the working process, whose features are the decrease in resistance, the increase in leakage current, and the formation of discoloration areas. During the process of electrical degradation, many times, the occurrence of electrical breakdown events leads to the production and growth of discoloration areas. In this paper, the high-voltage impact test of piezoelectric ceramics is carried out and the obtained discoloration areas are compared with the electrical degradation discoloration areas. It is found that the discoloration areas produced by the high-voltage impact test are the same as those obtained by the electrical degradation test, which shows that the grain arrangement is disordered and the grain boundary is fuzzy. The phase structure of the discoloration areas obtained by the two methods is consistent with that of the piezoelectric ceramic matrix, and it has been discovered that the formation of discoloration areas in the process of electrical degradation is a physical change process. The formation of discoloration areas is caused by the change in the local structure of piezoelectric ceramics, which leads to a decrease in light transmittance, and it is a direct cause. The formation of these discoloration areas will lead to a reduction in dielectric loss but has no effect on the piezoelectric constant, capacitance, and Curie temperature. The resistance of the ceramic sample decreases with the increase in load voltage.

Automated summary

The electrical degradation of piezoelectric ceramics leads to a decrease in resistance, an increase in leakage current, and the formation of discoloration areas. The disordered grain arrangement and fuzzy grain boundary are found to be the causes of discoloration areas formation. The phase structure of the discoloration areas is consistent with that of the piezoelectric ceramic matrix.