How do piezoelectric ceramics such as lead zirconate titanate work in ultrasonic devices?

Piezoelectric ceramics like lead zirconate titanate (PZT) function in ultrasonic devices by exploiting the converse piezoelectric effect, where an applied electric field induces mechanical strain in the material.12

These materials are processed through "poling," a technique where the ceramic is cooled through its Curie point under an applied electric field to align its internal dipoles. Because these ceramics lack a centre of symmetry, the application of an alternating electric field causes the crystal lattice to vibrate. When this field matches the material's natural mechanical resonance frequency, the resulting vibrations are significantly enhanced, allowing the device to generate ultrasound—sound waves with frequencies above 20 kilohertz.12

In ultrasonic systems, these vibrations are used to produce sound waves, while the direct piezoelectric effect—where mechanical stress generates a voltage—is used to detect reflected waves. This dual capability is fundamental to applications such as medical imaging, sonar, and industrial cleaning.12