Piezoelectric Voltage

After the poling process is complete, a voltage lower than the poling voltage changes the dimensions of the ceramic for as long as the voltage is applied.

A voltage with the same polarity as the poling voltage causes additional expansion along the poling axis and contraction perpendicular to the poling axis (fig. 2). A voltage with the opposite polarity has the opposite effect: contraction along the poling axis, and expansion perpendicular to the poling axis. In both cases, the ceramic element returns to its poled dimensions when the voltage is removed from the electrodes. These effects are shown greatly exaggerated in fig. 2.

Piezoelectric Voltage

After the poling process is complete, compressive and tensile forces applied to the ceramic element generate a voltage. Refer to fig. 3. A voltage with the same polarity as the poling voltage results from a compressive force (a) applied parallel to the poling axis, or from a tensile force (b) applied perpendicular to the poling axis. A voltage with the opposite polarity results from a tensile force (c) applied parallel to the poling axis, or from a compressive force (d) applied perpendicular to the poling axis.

The instances above can also be arranged to occur in the other two planes, i.e. thickness shear and face shear.

Generally two or more of these actions are present simultaneously. In some cases one type of expansion is accompanied by another type of contraction which compensate each other resulting in no change of volume. For example, the expansion of length of a plate may be compensated by a n equal contraction of width or thickness. In some materials, however, the compensating effects are not of equal magnitude and net volume change does occur. In all cases, the deformations are very small when amplification by mechanical resonance is not involved. The maximum displacements are on the order of a few microinches.