A phenomenological cohesive model of ferroelectric fatigue

Keywords:
ferroelectricity, fatigue, fracture, nucleation, cohesive

Abstract:
Ferroelectric materials are extensively used in a variety of sensor and actuator applications for their electro-mechanical coupling. Nevertheless, ferroelectric fatigue hinders the performance and reliability of ferroelectric devices. We present a model of electro-mechanical ferroelectric fatigue based on the postulate of a ferroelectric cohesive law that: couples for the first time mechanical displacement and electric-potential discontinuity to mechanical tractions and surface-charge density; and exhibits a monotonic envelope and loading-unloading hysteresis. We validate the model against experimental data for a simple test configuration consisting of an infinite slab acted upon by an oscillatory voltage differential across the slab and otherwise stress free. The model captures salient features of the experimental record including: the existence of a threshold nominal field for the onset of fatigue; the dependence of the threshold on the applied-field frequency; the dependence of fatigue life on the amplitude of the nominal field; and the dependence of the coercive field on the size of the component, or size effect. We expect the model to enhance current capabilities for assessing ferroelectric fatigue. We believe that it may also lay the ground for connecting the macroscopic response with micromechanisms.

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Nanotech 2006 Conference Program Abstract