What Is a Piezoelectric Crystal?

Piezoelectricity, discovered by the Curie brothers in 1880, is a property of certain crystals (like quartz, tourmaline, and some ceramics) in which mechanical stress displaces charge centres within the crystal lattice, producing a voltage. The effect is reversible: applying an electric field makes the crystal expand or contract. Quartz oscillators exploit this — a voltage causes a quartz crystal to vibrate at 32,768 Hz in watches, providing an accurate time base. Piezoelectric materials are also used in ultrasound transducers, inkjet printer heads, igniters, and smartphone accelerometers.