Piezoelectricity

Piezoelectricity (Qualitative)

When one pair of opposite faces of certain asymmetric crystals such as quartz crystal is compressed, opposite electric charges appear on the other pair of opposite faces of the crystal. On application of tension, the polarities of the charges reversed. This phenomenon of the development of charges as a result of the mechanical deformation is known as piezoelectric effect. Crystals which exhibit this property are called piezoelectric crystals. Quartz, ammonium phosphate and lead zirconate titanate are examples of piezoelectric materials.

The converse of piezoelectric effect is also true. If an electric field is applied across one pair of faces of piezoelectric crystal, it gets deformed along the direction of the other opposite pair of faces. If an ac field is applied, crystal vibrates with the frequency of the field. This effect is also called inverse piezoelectric effect which is used for the production of ultrasonic waves. Piezoelectric materials are also used in gas igniters, vibrators, sensors, detectors and in printer heads.