What Is a Piezoelectric Material?

Piezoelectricity (from Greek "piezein" meaning to press) was discovered by Jacques and Pierre Curie in 1880. In certain crystalline materials (quartz, tourmaline, and engineered ceramics like PZT), the crystal lattice lacks a centre of symmetry. When mechanical stress deforms the lattice, positive and negative charge centres are displaced relative to each other, generating a voltage across the material. The reverse also works: applying a voltage deforms the crystal. This bidirectional energy conversion has countless applications. Quartz crystal oscillators provide the timing signal in virtually every watch, clock, and digital device (vibrating at exactly 32,768 Hz). Piezoelectric sensors detect vibration, pressure, and acceleration in airbag triggers, medical ultrasound transducers, and earthquake seismometers. Piezoelectric actuators provide nanometre-precision positioning in atomic force microscopes. Barbecue and gas stove igniters use the spark from a struck piezoelectric crystal to light the flame.