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DF: Dielektrische Festkörper

DF 4: Internal Symposium “Ferroelectric Materials for Smart Structures”

DF 4.3: Vortrag

Dienstag, 28. März 2006, 10:30–10:50, K{\"O}N Farb

Nonlinear constitutive modeling of ferroelectric ceramics: the role of thermally activated processes — •A.Yu. Belov and W.S. Kreher — Institut für Werkstoffwissenschaft, TU Dresden, Hallwachsstr. 3, 01062 Dresden, Germany

The microscopic parameters characterising the interaction between domain walls and short-range obstacles in ferroelectric ceramics are assessed from the experimental data on the temperature dependence of the polarization hysteresis. The approach used is based on a nonlinear constitutive model, which accounts for thermally activated processes assisting the domain walls to overcome the energy barriers of the obstacles. Within the framework of the model the microstructure of ceramics is described effectively, employing the volume fractions of ferroelectric domains with different polarization orientations as structural variables, and its evolution is given in terms of rate equations for these variables. The average polycrystal properties are computed using a discrete orientations approximation (a set of representative orientations) for the distribution function of grain orientations. Assuming that the domain wall mobility depends on temperature according to the Arrhenius law, the microscopic parameters of the model, including the obstacle strength and activation energy, are extracted from the temperature dependence of the coercive field. The analysis of the experimental data for doped lead zirconate titanate (PZT) ceramics shows that for both soft and hard PZT compositions the domain wall motion near the coercive field is essentially thermally activated.

This work has been supported by the Deutsche Forschungsgemeinschaft.