The Piezoelectric Effect and Its Industrial Sensing Applications

1. Basic Principle

The piezoelectric effect occurs in certain materials where mechanical pressure generates an electrical charge. Discovered by the Curie brothers in 1880, the name derives from the Greek word "piezein" meaning to press.

Two modes exist:

• Direct effect: Mechanical stress deforms the material, shifting internal charges and creating voltage across the material's surfaces. This converts physical force into electrical signals.
• Converse effect: Applying an electric field causes the material to change shape slightly. This converts electrical input into precise mechanical motion.

2. Material Types

Three main categories exist. Stanford Advanced Materials (SAM) offers products across all categories.

Piezoelectric Crystals

Single crystals with regular atomic structure. Quartz remains the most common, offering stable performance across temperature changes with minimal signal drift. Lithium niobate and lithium tantalate work well for high-frequency applications. Crystals generally exhibit lower sensitivity than ceramics but provide better long-term stability.

Piezoelectric Ceramics

Polycrystalline materials, mainly lead zirconate titanate (PZT), dominate industrial applications. They offer significantly higher sensitivity than quartz. Manufacturers can adjust PZT composition to emphasise specific traits such as sensitivity or temperature resistance. Lead-free options like potassium sodium niobate (KNN) now exist for environmentally sensitive applications.

Piezoelectric Polymers

Materials like PVDF offer flexibility and toughness. While less sensitive than ceramics, they match water and tissue in acoustic properties. This makes them suitable for medical imaging and underwater sound systems.

3. Main Applications

Pressure Sensors

These measure rapid pressure changes in engines, hydraulic systems, and industrial processes. Quartz performs best in high-temperature environments requiring stable calibration over extended durations. PZT provides maximum sensitivity for detecting small forces in controlled conditions.

Ultrasonic Devices

Ultrasonic transducers both send and receive sound waves. Medical imagers, industrial flaw detectors, flow meters, and sonar systems all depend on them. Material selection relates to operating frequency and power requirements.

Vibration Sensors

Accelerometers detect motion and vibration by measuring force on a seismic mass. They monitor the integrity of bridges. They predict machinery failures.

They trigger vehicle airbags. They test aerospace components. They operate at frequencies from near zero to thousands of Hertz.

Precision Positioners

The converse effect enables positioning with nanometre accuracy. Atomic force microscopes, chip-manufacturing tools, fuel injectors, and print heads utilise piezoelectric actuators for speed and precision.

Energy Harvesters

Vibrations from machinery, vehicles, or human movement can generate small quantities of electricity. This powers wireless sensors where battery changes are impractical.

4. Material Selection Guide

For assistance in selecting materials, Stanford Advanced Materials (SAM) offers technical support based on decades of supply experience. Contact and tell us about your project.

5. Stanford Advanced Materials (SAM) Product Line

SAM supplies research laboratories and industry worldwide with piezoelectric materials meeting strict specifications.

Quartz Crystals

SAM provides quartz in AT, BT, SC, and custom cuts. Each cut exhibits different temperature behaviour. Applications include force sensing, acceleration measurement, and frequency control where stability is critical. [View Quartz Products]

Lithium Niobate

SAM's lithium niobate is available in congruent and stoichiometric grades. It is offered in several cuts, including 128° Y-X, Y-36°, X-cut, and Z-cut. High Curie temperature (>1 100°C) makes it suitable for surface acoustic wave filters and optoelectronic applications.

Lithium Tantalate

Enhanced temperature stability compared to niobate makes SAM's tantalate the choice for telecommunications filters and infrared detectors. Available in 42° Y-cut, X-cut, and other orientations up to 4 inches diameter. [View Lithium Tantalate Products]

PMN-PT Single Crystals

These relaxor crystals achieve d₃₃ values above 1 500 pC/N and coupling factors above 0.90. Medical ultrasound transducers gain bandwidth and sensitivity.

Actuators achieve greater displacement. Energy harvesters capture more power.

PZT Ceramics

SAM offers both hard and soft PZT compositions. Hard PZT handles high power in ultrasonic cleaners and welding.

Soft PZT provides maximum sensitivity for sensors. Available as discs, plates, tubes, and custom shapes.

Custom Services

SAM grows crystals to customer specifications. Need specific orientation? Doping level? Dimensions? Electrode pattern? The technical team will collaborate with you. [View Custom Services]

References

1. Curie, J. and Curie, P. (1880). "Développement par compression de l'électricité polaire dans les cristaux hémièdres à faces inclinées." Bulletin de la Société Minéralogique de France, 3(4), pp. 90-93.

2. Jaffe, B., Cook, W.R. and Jaffe, H. (1971). Piezoelectric Ceramics. Academic Press, London.

3. IEEE Standard on Piezoelectricity (1987). ANSI/IEEE Std 176-1987. The Institute of Electrical and Electronics Engineers.

4. Uchino, K. (2017). Piezoelectric Actuators: Principles and Applications. MDPI Books, Basel.

5. Safari, A. and Akdogan, E.K. (2008). Piezoelectric and Acoustic Materials for Transducer Applications. Springer Science+Business Media, New York.

6. Rödel, J., Webber, K.G., Dittmer, R., Jo, W., Kimura, M. and Damjanovic, D. (2015). "Transferring lead-free piezoelectric ceramics into application." Journal of the European Ceramic Society, 35(6), pp. 1 659-1 681.

7. Tressler, J.F., Alkoy, S. and Newnham, R.E. (1998). "Piezoelectric sensors and sensor materials." Journal of Electroceramics, 2(4), pp. 257-272.

8. Damjanovic, D. (1998). "Ferroelectric, dielectric and piezoelectric properties of ferroelectric thin films and ceramics." Reports on Progress in Physics, 61(9), pp. 1 267-1 324.

9. Zhang, S. and Li, F. (2012). "High performance ferroelectric relaxor-PbTiO₃ single crystals: Status and perspective." Journal of Applied Physics, 111(3), 031301.