Page "Piezoelectricity" Paragraph 1

The piezoelectric effect is understood as the linear electromechanical interaction between the mechanical and the electrical state in crystalline materials with no inversion symmetry.

The piezoelectric effect is a reversible process in that materials exhibiting the direct piezoelectric effect ( the internal generation of electrical charge resulting from an applied mechanical force ) also exhibit the reverse piezoelectric effect ( the internal generation of a mechanical strain resulting from an applied electrical field ).

For example, lead zirconate titanate crystals will generate measurable piezoelectricity when their static structure is deformed by about 0. 1 % of the original dimension.

Conversely, those same crystals will change about 0. 1 % of their static dimension when an external electric field is applied to the material.

The inverse piezoelectric effect is used in production of ultrasonic sound waves.