Piezoelectricity, << pee `ay` zoh ih `lehk` TRIHS uh tee, >> is the ability of some materials to convert mechanical energy to electric energy and vice versa. Applying a mechanical force to such a material—squeezing it, for example—can create a voltage along the material’s surface. This conversion of mechanical force into voltage is called the direct piezoelectric effect. On the other hand, applying a voltage to a piezoelectric material can cause the material to change shape. This process is called the indirect or reverse piezoelectric effect.
Two brothers, the French physicists Pierre and Jacques Curie, discovered the piezoelectric effect in crystals of quartz, Rochelle salt, and other materials in the early 1880’s. Since then, scientists and engineers have identified many piezoelectric materials. The most widely used include the ceramic materials lead zirconate titanate, often called PZT, and barium titanate.
In the early 1910’s, the French physicist Paul Langevin proposed using piezoelectric crystals to create sonar devices, one of piezoelectricity’s first important uses. The devices applied a voltage to the crystals that varied over time, causing the crystals to vibrate through the indirect piezoelectric effect. The vibrations produced sound waves used to detect objects at a distance.
Today, many devices make use of piezoelectricity. Electric guitars use the direct piezoelectric effect to convert the vibration of their strings into electrical signals. Similarly, piezoelectric materials convert sound vibrations to electrical signals in microphones. Many automatic lighters produce a spark by sharply squeezing a piezoelectric material. Some cameras and other optical devices use the indirect piezoelectric effect to move and focus lenses and mirrors with great precision.
