Piezoelectricity and Piezoelectric Transducers

Piezoelectricity is the property of certain crystalline and ceramic materials to generate an electric charge when subjected to mechanical stress. The effect is reversible: applying a voltage to the same material causes it to deform mechanically. This direct and converse piezoelectric effect was discovered by the Curie brothers in the 1880s. Common piezoelectric materials include quartz, certain ceramics such as lead zirconate titanate (PZT), and polymer films, each chosen for its sensitivity, stability or flexibility.

Because the effect converts between mechanical and electrical energy, piezoelectric elements work both as sensors and as actuators. As sensors they respond to pressure, force, acceleration and vibration, producing a charge proportional to the applied stress; this makes them well suited to dynamic measurements rather than steady, constant loads, since the generated charge leaks away over time. As actuators they convert an applied voltage into precise, small displacements, used in positioning stages, valves and benders.

A major application is the generation and detection of sound and ultrasound. A piezoelectric transducer driven by an alternating voltage vibrates and radiates acoustic waves, and the same element can detect returning echoes by producing a voltage. This underlies ultrasonic distance sensing, cleaning, medical imaging and non-destructive testing. Piezoelectric film transducers, being thin and flexible, are used where conformable sensing or wide-band acoustic response is needed. Stacked elements multiply the available displacement or force for actuator use.

Frequently asked questions

What is the difference between the direct and converse piezoelectric effects?

The direct effect produces a charge from applied mechanical stress, while the converse effect produces mechanical deformation from an applied voltage.

Why are piezoelectric sensors best for dynamic measurements?

The charge they generate gradually leaks away, so they respond well to changing forces and vibration but cannot hold a reading for a steady, constant load.

How does a piezoelectric transducer produce ultrasound?

An alternating voltage makes the element vibrate mechanically, radiating acoustic waves; the same element can also convert returning echoes back into a voltage.