Method for the estimation of the total displacement of ferroelectric actuators under mixed thermal and electrical loading

The temperature behavior of the displacement of ferroelectric actuators, when operating at varying temperature, is affected by several factors. First of all, there are changes in field induced strain with temperature. However, the total displacement of an actuator depends also on the poling strain and strain from thermal expansion. These two effects are coupled, because thermal expansion is anisotropic and therefore related to the poling texture. At high temperature the texture is subject to changes from thermal depolarization, resulting in additional effects on strain. Direct measurement of the displacement under mixed thermal-electrical loading requires advanced measurement techniques presently not available. Therefore, a method is suggested, how to estimate the total displacement from separate, temperature dependent measurements of remanent strain, field induced strain, strain from thermal depolarization, and thermal expansion in the unpoled state. The results are related to typical operating modes of ferroelectric actuators. With respect to temperature stability of the performance design rules for materials development are derived. (C) 2008 Elsevier B.V. All rights reserved.