Depth dependence of piezoelectric activity in poly(vinylidene fluoride) transducers: Control and measurement

Abstract

Double-layer and multilayer poling experiments have been performed to determine the depth dependence of piezoelectric activity in poly (vinylidene fluoride) (PVF2) films. The depth dependence of activity is highly dependent on poling field and time. Removal of the poling field before cooling alters the activity distribution. When central conductive layers are present during poling, cathode activity is increased. When a thermal gradient occurs across the sample’s thickness during poling, the cool side is the more active. A bulk measurement of activity asymmetry in transducer films is described, and use of asymmetric films as flexure devices is discussed. Reversing the field during poling is useful in increasing asymmetric activity.