Internal bias in acceptor-doped BaTiO3 ceramics: Numerical evaluation of increase and decrease

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Abstract
The buildup of the internal bias in time and the decrease of the internal bias by forced switching of the polarization by an ac field have been described empirically by various authors. Both time dependencies can now be derived from a simple model, proposed recently by G. Arlt and H. Neumann [Ferroelectrics 87, 109 (1988)]. In this model an oxygen vacancy is a mobile particle in the oxygen octaeder which encloses an acceptor ion on the Ti site. The associate acceptor/oxygen vacancy is an electric and elastic dipole which can orient in the polarized ferroelectric material. The differential equation for Ei(t) is solved for the increase and for the forced decrease of the internal bias. The two solutions are completely different time laws. They agree well with former and new observations. Characteristic parameters of the model can be derived from experimentally observed time dependencies.