Interaction of point defects in piezoelectric materials – numerical simulation in the context of electric fatigue

The paper is concerned with the problem of electric fatigue in functional materials such as piezoelectric sensors and actuators. The fatigue degrades electromechanical properties with an increasing number of working cycles during which ionic and electronic charge carriers interact with each other within the bulk and on the interfaces of a material. This, in turn, influences local electric and mechanical fields coupled via the piezoelectric effect. It is assumed in the paper that the electric charges (vacancies) can be modelled as point defects, which tend to agglomerate and finally form clusters, especially in the vicinity of electrodes. As a result, the piled up defects affect the distribution of polarisation. To solve the problem quantitatively, the analysed system is discretised with a grid of square cells and then transformed by FFT. Several numerical examples are formulated. Migration of a single defect, attraction of two and clustering of more point defects are thoroughly discussed and illustrated in the paper.