A phenomenological cohesive model of ferroelectric fatigue

Division of Engineering and Applied Science, Graduate Aeronautical Laboratories, California Institute of Technology, MS205-45, 91125, Pasadena, CA, USA; Laboratori de Cà lcul Numèric, Departament de Matemà tica Aplicada III, Universitat Politècnica de Catalunya, E-08034, Barcelona, Spain
Acta Materialia (Impact Factor: 3.94). 02/2006; DOI: 10.1016/j.actamat.2005.10.035
Source: OAI

ABSTRACT We develop a phenomenological model of electro-mechanical ferroelectric fatigue based on a ferroelectric cohesive law that couples mechanical displacement and electric-potential discontinuity to mechanical tractions and surface-charge density. The ferroelectric cohesive law exhibits a monotonic envelope and loading-unloading hysteresis. The model is applicable whenever the changes in properties leading to fatigue are localized in one or more planar-like regions, modelled by the cohesive surfaces. 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. Our results, although not conclusive, indicate that planar-like regions affected by cycling may lead to the observed fatigue in tetragonal PZT. Peer Reviewed Postprint (author's final draft)

  • Biophysical Journal 02/2011; 100(3). · 3.83 Impact Factor
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    ABSTRACT: We propose a phase-field model for the coupled simulation of microstructure formation and evolution, and the nucleation and propagation of cracks in single-crystal ferroelectric materials. The model naturally couples two existing energetic phase-field approaches for brittle fracture and ferroelectric domain formation and evolution. The finite-element implementation of the theory in two dimensions (plane-polarization and plane-strain) is described. We perform, to the best of our knowledge, the first crack propagation calculations of ferroelectric single crystals, simultaneously allowing general microstructures to develop. Previously, the microstructure calculations were performed at fixed crack configurations or under the assumption of small-scale switching. Our simulations show that this assumption breaks down as soon as the crack-tip field interacts with the boundaries of the test sample (or, in general, obstacles such as defects or grain boundaries). Then, the microstructure induced by the presence of the crack propagates beyond its vicinity, leading to the formation of twins. Interactions between the twins and the crack are investigated under mechanical and electromechanical loadings, both for permeable and impermeable cracks, with an emphasis on fracture toughening due to domain switching, and compared with experiments.
    Acta Materialia. 07/2011; 59(12):4733–4746.
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    ABSTRACT: The evolution of the fatigue behaviors in Bi3.5Nd0.5Ti3O12 (BNT) ferroelectric thin films deposited on Pt(111)/Ti/SiO2/Si(100) substrates by chemical solution deposition (CSD) method effected by amplitude, frequency and profile of the driving electric field were reported. It is found that the switching with lower frequency and higher amplitude of the external voltages resulted in higher fatigue rates and only bipolar waveform type voltage can result in fatigue, whereas a unipolar voltage cannot. An empirical function with N/f is proposed in the frequency-dependence of polarization fatigue, where N is the number of switching cycles and f is the frequency of driving. It is indicated that injected charges from electrodes into films, the trapped charges, and suppression of the seeds of opposite domain nucleation are the main mechanism of fatigue in ferroelectric BNT thin films.
    Surface Review and Letters 04/2012; 18(05). · 0.37 Impact Factor

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