Bipolar strain hysteresis of poled composites with Nd-Mn-doped PZT fibres

The resulting 1-3-composites were poled with constant electric field. Measurements of strain and polarisation were done using a sinusoidal voltage of high amplitude. Instead of a shifted strain hysteresis (butterfly loop) an asymmetric strain-field relation was observed. The asymmetry depends on the direction of the applied voltage. For the half wave with voltage parallel to former poling voltage the strain curve is linear. For the other half wave the strain curve inflates and there is a region with no change of strain. Possible explanations for the asymmetric strain behaviour are discussed.