Models and Mechanisms
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The present chapter is essentially the discussion of the multiple factors influencing fatigue in ceramic ferroelectrics. It is thus in large parts also a review of relevant literature. The intention is to provide more than just a mere presentation of a single model, but the attempt to correlate the vast body of knowledge on particular aspects of fatigue to the relevant mechanisms.
KeywordsOxygen Vacancy Domain Wall External Field Dislocation Loop Coercive Field
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- 1.A small polaron is a highly localized electron state inducing a strong deformation of its neighboring environment. It generates its own energy minimum by deforming its elastic environment. For any polaron state to exist, the time of interaction with phonons has to be long enough so that at least one full wavelength of the phonon can interact with the electron. Thus, only slow electrons (low k-value) can form polarons. Along with the elastic deformation around a polaron an induced polarization of the environment occurs. A large polaron does not interact as strongly with its environment and is therefore more mobile. In semiconductors with wide band gap also holes can be considered hole polaron states of inverse charge, because they interact with their elastic environment in a similar manner (Hellwege, 1988; Tsuda et al., 2000).Google Scholar