On the Cutting Edge: Piezoelectric Ceramics
ITT Exelis Acoustic Systems in Salt Lake City, Utah, has been manufacturing piezoelectric ceramics for over 60 years. Exelis specializes in the production of lead zirconate titanate ceramic (PZT). Minerals are first mined from the earth, then refined and mixed to become man-made materials developed specifically to take advantage of the piezoelectric effect.
This highly specialized ceramic is a unique material that produces an electric charge upon the application of pressure. Squeezing a crystal produces a voltage that corresponds to the amount of pressure applied. Since piezoelectric materials are reciprocal in nature, it is possible to have the following conditions:
• If a voltage is supplied to the piezoelectric material, it will produce movement (a source of sound)
• If pressure to is applied to the piezoelectric material, it will produce a voltage that can be used for detection purposes or energy production
The piezoelectric phenomenon occurs naturally in crystals such as quartz. However, natural piezoelectric materials require large single crystals to make them useful. Growing these is a time-consuming and expensive process that is very difficult to control. By forcing a number of small crystals to behave as one large crystal, a useful piezoelectric material is obtained that can be tuned for very specific applications.
Originally developed for use in sonar applications, this technology has been applied to many industrial and medical applications (see Figure 1). For example, our ceramic composition is used to create an electric field used in the treatment of some forms of cancer.
Exelis piezoceramic is also used as a sensor component in sonar, which makes it possible to explore the depths of the ocean. Our ceramic was also a critical component in the Apollo missions. The lunar lander used piezoceramic to measure the density of the crust in the first moon landing.
Most people are familiar with ultrasound, but few understand that piezoelectric materials make it possible. Piezoelectric ceramic is machined into shapes that vibrate at a very specific frequency to create a beam of acoustic energy that travels into any material. This beam reflects from regions within that material that have different acoustic properties. The returned beam is measured by the amount of voltage created as it impacts the piezocrystal. A picture is then formed that allows for diagnosis without invasive surgery.
This technique has been applied to medical applications for many years. It is also used to diagnose defects in materials for industrial applications such as the nondestructive testing (NDT) of welds, as well as measuring thickness, fluid level or the presence of gas bubbles in a fluid.
Piezoelectric ceramic is currently used in almost every area of daily life. Cell phones use piezoceramic for speakers and microphones. The buttons activated by pedestrians when crossing the street contain piezoceramic to measure the pressure of a human hand. Acoustic pickups for music recording would not be possible without piezoceramics.
ITT Exelis Acoustic Systems maintains a world-class facility in Salt Lake City that produces over 150,000 kg of ceramic per year. This equates to over a million different piezoceramic components annually. Manufacturing this much material annually requires discipline, dedication and a highly trained workforce. The use of modern manufacturing processes and systems such as Lean Six Sigma have earned the company a reputation for extremely high quality and innovative ideas for future applications.
Evolving customer requirements continue to lead the way for future focused projects such as energy harvesting, sterilization/high level disinfection, and cancer treatment. Potential future applications include sensors with lifetimes measured in decades with no requirement for battery replacement, hospital rooms and other sensitive areas sanitized in minutes to reduce infections, and cancer treatment with focused chemotherapy and minimized sided effects. The only limit for the future is human imagination.
For more information, contact ITT Acoustic Systems at 2645 S. 300 W., Salt Lake City, UT 84115; call (801) 486-7481; or visit http://acousticsystems.itt.com.