Pyroelectric hysteresis in ferroelectric polymers

The effect of a varying bias field on the pyroelectric properties of sub-micron ferroelectric polymer films has been investigated. The magnitude and phase of the pyroelectric signal reflect the hysteresis in the polarisation resulting from the bias field. The coercive field can be precisely measured by observing the abrupt 180 degrees phase change in the pyroelectric signal as the polarisation reverses. For 100 nm films, the coercive field is 50 MV m(-1), which is similar to the value observed in films with thickness greater than 1 mu m As the bias field is reduced to zero the pyroelectric response drops by around one-third, suggesting the need to keep the bias field present in pyroelectric devices based on such films. Repeated cycling of the bias field leads to a slight decrease in the maximum pyroelectric response, resulting from fatigue in the films. (C) 1998 Elsevier Science S.A. All rights reserved.