Piezoelectricity and Its Applications - IntechOpen

Jun. 16, 2025

Piezoelectricity and Its Applications - IntechOpen

1. Introduction

Technical application of Piezoelectricity phenomenon first discovered by Pierre and Jacques curie and Jacques curie in [1] and thereafter soon understood from the crystallographic point of view had a very slow start because for decades only a few suitable materials were available. In spite of their small piezoelectric effect, quartz crystals continue to dominate as components for frequency control since the early days of radio engineering [2], this is due to their extremely sharp resonance curves, which are stable with respect to temperature and aging. The first ferroelectric material, Rochelle Salt [3] was found out to the suitable for broadband applications in the year .Stability problems encountered with these crystals, which are produced from aqueous solutions, restrict their application to phonograph pick-ups.

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Over the past period the spheres of application of piezoelectric materials in modern techniques have been considerably enlarged. In this relation the requirements to their properties are continuously growing. A great number of the piezoelectric materials have been developed in several countries, yet research in this field is still in active. The efforts of researchers are concentrated on the problem of purposeful development of the materials with desirable combination of their properties. The wide spread application of the piezoelectric effect is based on ferroelectric ceramic materials can be attributed to three main facts:

The Piezoelectric effect particularly large in the ferroelectrics.
Ceramics can be produced cost effectively. Most of these materials are either impossible or at best very difficult to produce in mono crystalline form.
Ceramic materials offer a high degree of variation concerning geometrical shaping on the one hand and physical properties on the other hand by virtue of mixed-crystal formation, creation of differing grain structures, and interaction of various ferroelectric or non- ferroelectric phases.

At present piezoelectric materials based on Barium Titanate (BaTiO3). Lend Zirconate-Lead Titanate (PZT) solid solutions and multi component solid solutions relating to the Perovskite type crystal structure and containing, as a rule, lead titanate or lead zirconate, are mainly used [3].

Most of the improvements in the properties for particular application in the piezoceramics have been achieved either by partially replacing the constituent atoms by other atoms or doping with a small quantity of purity additives. Broadly speaking, all these methods may be considered to the control the ceramic characteristic properties by impurity doping.

Piezoelectricity is the additional creation of an electric charge by the applied stress; this is the direct piezoelectric effect. The charge is proportional to the force, and it is therefore of opposite sign for compression and tension. In terms of dielectric displacement D (charge Q per unit area A) and stress T, it may be written as.

D=Q/A=dTE1

There is a converse effect. An applied field E produces a proportional strain S, expansion or contraction depending on polarity.

S=dEE2

Therefore, the piezoelectric constant ‘d’ (Piezoelectric strain coefficient) which is numerically identical for both direct and converse effects.

d=D/T=S/EE3

Another frequently used piezoelectric constant is g (piezoelectric voltage coefficient), which give the field produced by a stress and is related to the ‘d’ constant by the permittivity (ε).

g=d/εE4

Additional piezoelectric constants which occasionally used are ‘e’ which relates stress T to field E, and ‘h’ which relates strain S to field E.

T=−eEE5T=−hSE6

Actual definitions are.

d=∂S/∂ET=∂D/∂TEE7g=−∂E/∂TD=∂S/∂DTE8e=∂T/∂ES=∂D/∂SEE9h=−∂T/∂DS=−∂E/∂SDE10

For ceramics and crystals the elastic, dielectric and piezoelectric constants may differ along different axes. For this reason, they are expressed in tensor form.

The hydrostatic strain constant dh is related to d33 and d31 as follows:

dh=2d31+d33E11whered33=∂D3/∂T3E=∂S3/∂E3Td31=∂D3/∂T1E=∂S1/∂E3T

Possibly the best single measurement of the strength of a piezoelectric effect is the electromechanical coupling factor K. When an electric field is applied, it measures the fraction of the electrical energy converted to mechanical energy (or vice versa when a crystal or ceramic is stressed). The actual relationship is in terms of K2

K2=Electrical energy converted to mechanical energyInput electrical energyK2=Mechanical energy converted to electrical energyInput mechanical energy

The piezoelectric, elastic and dielectric constants of poled ceramics are strongly temperature dependent. Heating through the Curie point destroys the effect of poling and causes the piezoelectric properties to disappear [4]. If the sample is heated to just below the Curie point the piezoelectric properties are degraded. A remanant piezoelectric effect produced by polling an initially random orientation ceramic is a strong evidence for ferroelectricity 900 walls contribute to the piezoelectric effect since their movement is accompanied by dimensional change and not walls because there will be no dimensional change [5]. Ferroelectric materials with high Curie temperature are highly desirable to construct transducers for high temperature piezoelectric applications.

2. Piezoelectricity

Certain crystals become electrically polarized (i.e electric charges appear on their surfaces) when stressed. This phenomenon discovered in by Pierre and J. Curie is called the piezoelectric effect and the crystals as the piezoelectric crystals Quartz, rochelle salt, tourmaline are the familiar piezoelectric substances. The inverse effect--that these crystals become strained when polarized has also been observed.

Piezoelectric strains are very small, and the corresponding electric fields are very large. In Quartz for example a field of V/cm produces a strain of the order of 10−7. Conversely small strains can produce large electric fields.

To understand the origin of the piezoelectric effect, the distribution of the ionic charges of a crystal about their lattice sites. Normally, the distribution is symmetrical, and the internal electric field is zero. But when the crystal is stressed, the charges are displaced. In a piezoelectric crystal this displacement distorts the original charge distribution in such a way that it is no longer symmetrical - for a quartz crystal. A net polarization results in such crystals and when observing the piezoelectric effect. In other crystals, on the other hand, the distribution of charges maintains its symmetry even after the displacement - for a non piezoelectric crystal. Such crystals exhibit no net polarization and hence no piezoelectric effect [6].

It follows that the piezoelectric effect is related to crystal symmetry. The symmetry element involved is essentially the center of inversion. A crystal can exhibit piezoelectric effect only if its unit cell lacks a center of inversion. This is because when there is no center of inversion, only then the charge distribution is distorted so as to produce polarization. However if the center of inversion is present, there is no charge distortion hence no polarization.

It can be proved that of the 32 crystal classes, 21 are non centro symmetrical but since one of these 21 is highly symmetric in other respects, it is piezoelectrically excluded, leaving only 20 piezoelectric classes. However, all crystals belonging to these 20 classes are not observably piezoelectric - in some crystals the piezoelectric effects are too small to be detectable. Thus, the lack of inversion center is a necessary but not sufficient condition to guarantee piezoelectricity.

Piezoelectric effect is extensively used to convert the electric energy into mechanical energy and vice-versa i.e. the piezoelectric substances are used as electromechanical transducers. For instance it is an electric signal that is applied to one end of a quartz rod, the variations in strain generated in the rod in consequence of the effect propagate down the rod constituting what is known as mechanical wave or an acoustic wave. Another important application of piezoelectrics is their use as highly stable oscillators for frequency control [7]. If a quartz crystal is subjected to an alternating voltage at one of its resonant frequencies the crystals will suffer expansion and contraction alternately in consequence of the effect and thus the oscillations of the crystals will be set up. The frequency of these oscillations depends on the dimensions of the specimen and the elastic constants of the material and is stable. Specially cut quartz discs are generally used for this purpose.

Ferro electricity versus piezoelectricity [8]:

In piezoelectricity the crystal is polarized by the application of an external stress whereas in ferroelectricity the source of polarization is the dipole interaction energy itself.
Both the phenomena occur in noncentrosymmetric crystals, which are 20 in number. Piezoelectricity occurs in all the 20 crystals whereas ferroelectricity only in 10 namely those which provide a favorable axis of polarity.
All ferroelectrics are therefore piezoelectric but all piezoelectrics are surely not ferroelectric for example Tourmaline is piezoelectric but not ferroelectric at all.
The piezoelectric coefficient is the ratio of the setup charge to the stress applied to a crystallographic axis. The ferroelectrics have very large piezoelectric coefficients.

The phenomenon of piezoelectricity was discovered just over a hundred years ago by the Curie brothers, Pierre and Jaques. The science of Piezoelectricity has proceeded at an uneven face in these one hundred years. Periods of rapid progress have been followed by periods of slow development and sometimes even by periods of no development (Incidentally, this is characteristic of all branches of science). Every time that piezoelectricity has appeared to be exhausted as a science, the discovery of new piezoelectric effects or new piezoelectric materials initiated a new stage of rapid development and opened up new areas for the application of piezoelectricity. Piezoelectricity is currently enjoying a great resurgence in both Fundamental Research and Technical applications.

Piezoelectricity is one of the basic properties of crystals, ceramics polymers and liquid crystals. There are several ways to describe the piezoelectric effect [9]. Perhaps the most common definition is that a material is piezoelectric if the application of an external mechanical stress causes the development of an internal dielectric displacement. This displacement is manifested as an internal electric polarization or a surface electric charge Because of the way in which the elastic stress and dielectric displacement transform during coordinate axis rotation (Figure 1) the piezoelectric constants describing the linear relationship form a third order tensor. A simplified mathematical formulation of the piezoelectric effect is given below. More detail treatments of the piezoelectric effect and Converse effect can be found in texts.

It should be noted that the piezoelectric effect is strongly linked to the Crystal symmetry. All crystals are arranged into 32 point groups. Crystals belonging to the 11 centro symmetric point groups cannot show a piezoelectric effect. Crystals belonging to the non centro symmetric point group O also do not exhibit a piezoelectric effect. Nearly all other non metallic crystals belonging to the remaining 20 point groups exhibit a piezoelectric effect of some magnitude, although some of the effects are very small.

The piezoelectric phenomenon can be described as.

Pi=P0i+jkEdijkTjkE12

Where Pi is a component of the polarization vector, P0i the spontaneous polarization and Tjk is the stress tensor component. The coefficient dijk are called the piezoelectric Coefficient and are third rank tensor components.

Piezoelectric materials that are currently receiving much scientific attention include piezoelectric semiconductors, such as gallium arsenide, which have a wide range of interesting properties [10]. An existing goal with these materials is to integrate the piezo device and the semiconductor components on the same substrate. The last decade has witnessed an explosive expansion in research on surface acoustic waves. Most recently, the research has concentrated on layered systems containing piezoelectrics. Another important application of surface acoustic waves has been the development of miniature high-frequency “bulk structure” filters using Lithium niobate and Lithium tantalate crystals for use in consumer electronic applications.

Research into “bulk structure” surface acoustic wave resonators is currently a very active area. Piezoelectric Polymers, thin films and composites are becoming increasingly important. This is evidenced by a series of recent International conferences devoted to PVF2 and other piezoelectric polymers.

Since piezoelectricity was first discovered the applications of piezoelectric materials have mushroomed. Langevin’s work opened the large field of ultrasonics, which now includes detection, nondestructive evaluation, acoustic electricity, acousto optics, and imaging, signal processing, physical acoustics, medical acoustics etc.

Early Works By Cady and Nicolson lead to frequency control including resonators, oscillators and filters [11]. This field initially utilized low frequencies about 100 kHz. As time progressed, higher frequencies were needed and used. The majority of the presently mass produced high frequency piezoelectric filters are based on the Onoe theory of the multimedia resonator. It should be noted that the Onoe theory was inspired by Schockley’s theory of energy traps.

Today piezoelectric devices are found in television sets, radios, wristwatches, small computer games, automobiles etc. Many communications and navigation systems used large numbers of very precise piezoelectric resonators for frequency control, generation and selection.

It can be observed that even with quartz the original piezoelectric material, the rate of improvement of the properties of these devices is still in an accelerating phase. For instance, the stability of quartz frequency sources has improved by an order of magnitude every five or six years.

Piezoelectric materials have always played a very significant role in acoustics. In recent times, they have found widespread application as generators, transmitters and detectors of surface acoustic waves.

Of the many biological materials which exhibit piezoelectricity bone belongs to the best investigated ones. Bur has measured various complex piezoelectric constants of bovine bone as a function of frequency, temperature and relative humidity. The presence of water in bone in some piezoelectric constants gives rise to the occurrence of piezoelectric relaxation in others it shifts the relaxation frequency as does the temperature. This piezoelectric relaxation has been qualitatively explained by the two-phase model too. The losses in this case are attributed to a Maxwell Wagner dispersion, which occurs as a result of ionic conduction.

It may appear that the physical mechanism of piezoelectric relaxation by electrical and mechanical interactions between different phases is different from the piezoelectric relaxation as described in the preceding chapters. The basic elements of the piezoelectric relaxation however, are compatible for molecular point defects for two-dimensional defects like domain boundaries and for three-dimensional defects as are the finely dispersed to phase materials. In any case there is a coupling between electrical and mechanical losses, which can be described by the relaxation of defects which are simultaneously as well electric as elastic dipoles. The heterogeneous system entails a higher degree of complexity, example superposition of uncoupled losses, losses by electric conduction, local field effects orientation distributions and others. Therefore the theoretical treatment is clearer in the two-phase model.

Piezoelectric ceramics are prepared for fabricating the electromechanical transducers used in the mechanical frequency filters that find application in long-haul Communications systems. These ceramics have to satisfy specifications that can only be met by utilizing all the possibilities offered by the physical effects of the ferroelectric materials. The required positive temperature coefficient of the frequency constant is realized with the aid of elastic anomalies in the region of ferroelectric phase transitions.

Quartz resonators have been adapted for communications, but in recent years mostly for wrist watches and clocks since the quartz-oscillator circuit which incorporates a piezoelectric quartz crystal resonator has a very stable frequency. Thanks to quartz resonators, time accuracy of wrist watches has been improved rapidly. Quartz resonators for wristwatches and clocks amount to over 60% of total quartz resonators manufactured in Japan. This paper touches upon the characteristics, details of technical advancements, the analysis methods, the manufacturing technique and finally the future trend of quartz resonators for wristwatches.

Recently electronic wrist watches have spread far and wide, small and beautiful ones with high accuracy and many functions in particular. It owes development of various watch parts including the Integrated circuit. Among them the development of the quartz resonator for wristwatches, which produces the time (frequency) standard, is especially splendid.

Elastic vibration of a quartz resonator is transformed into electric Vibration by piezoelectricity because quartz crystal is stable against the ambient temperature, elapsed time and other various environments; frequency of a quartz resonator oscillator is extremely stable. Therefore it has been used in the fields of wireless communications and recently adapted for wrist watches and clocks. It shows the percentage of quartz resonators by fields produced in Japan. As described, quartz resonators for wrist watches and clocks amount to 64.6% of the total number and 40.4% of the gross sales.

The Top Uses of Piezoelectricity in Everyday Applications

What do cell phones, diesel fuel injectors, acoustic guitar pickups, grill igniters, ultrasonic transducers, vibration sensors, certain printers, and musical greeting cards all have in common? Besides being electronic devices, all of these applications utilize piezoelectricity in some way. Let’s explore how piezoelectricity works and look at some applications and examples of piezoelectric materials in day to day life.

How Does Piezoelectric Material Work?

Dating all the way back to and the groundbreaking work of brothers Pierre and Jacques Curie, the piezoelectric effect refers to the ability of specific materials — such as quartz, tourmaline, topaz and Rochelle salt — to produce an electric charge when subjected to mechanical stress. The term “piezo” can even trace its roots back to ancient Greek, where its meanings relate to actions of pushing, squeezing and pressing.

No piezoelectric effect explanation would be complete without a brief discussion of what piezoelectric devices are as well. Today, thanks to the additional development of manmade piezo materials — including piezoelectric ceramics — the applications of piezoelectricity in electronic devices are growing at an exciting pace.

How Does the Piezoelectric Effect Work With Sensors and Motors?

To begin with, there’s probably no more popular application of the piezoelectric effect than as a high voltage power source in electric cigarette lighters and gas grills. In these cases, a hammer strikes a piece of piezo material, which then produces enough current to create a spark that ignites the flammable gas in its presence. However, in other applications like sensors, the hammer as an exciter of the piezo material is typically replaced by other forms of energy like sound waves — including ultrasound.

When they’re put to work in sensors, piezo materials can detect even some of the most minute disturbances and anomalies, which makes them ideal devices in industrial nondestructive testing and medical imaging.

In other instances, piezoelectric motors can perform highly precise and repeatable movements. This ability makes them excellent devices for the precision movements of sensitive optical devices like telescopes and microscopes.

What are the Advantages and Disadvantages of Piezoelectricity?

Compared to other electronic components, piezoelectric devices have several advantages, as well as some disadvantages.

Their advantages include the following aspects:

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No external power source required: Thanks to their ability to produce a voltage when acted upon by a force, piezo materials require no external power source.
Easy installation: With small dimensions, they’re a great fit and easily installed in high-density electronic devices.
Responsiveness to high-frequencies: Compared to other devices, piezo materials have a substantially higher frequency response — which makes them wonderfully responsive in even the most demanding situations.
Highly flexible materials: Most piezo materials can be constructed in a wide variety of shapes and sizes, so they’re highly useful across various applications and fields.

Piezo materials also display the following limitations or disadvantages:

Small amount of electric charge: Though they’re self-generating, piezo materials produce fairly small electric charges, which means a high impedance cable is required to connect them to an electrical interface.
Environmental conditions affect performance: Piezo materials are affected by temperature and changes in humidity. Plus, while in the static condition, they can’t measure output.
Output is relatively low: While some piezo materials produce more output than others, they’re all relatively low. For their use to be optimized, an external circuit will often be required.

What are Common Uses for Piezoelectricity

What are the Uses of Piezoelectric Actuators in Industrial Applications?

The industrial sector often employs piezoelectric sensors for a variety of uses. Some common, everyday uses include:

Engine Knock Sensors — Engine manufacturers are constantly facing challenges related to the control of engine parameters. Under the wrong circumstances, gasoline engines are susceptible to an undesirable phenomenon known as detonation. When detonation occurs, the air/fuel charge explodes instead of burning smoothly thereby damaging the engine. Historically, this is why most manufacturers designed engines with conservative operational margins at the expense of efficiency — it was to avoid this notorious problem.

With the development of better control systems, the relevant engine parameters may be adjusted in real-time to maximize efficiency and power. If detonation begins to occur, piezoelectric knock sensors can be employed to sense the detonation before it becomes problematic. This gives control systems time to make the required adjustments.

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Pressure Sensors — In nearly any application requiring the measurement of dynamic pressure changes, using piezoelectric pressure sensors yields more reliable results than using conventional electromechanical pressure sensors. This is because piezoelectric devices have a high frequency response and signal conversion without requiring any bellows, diaphragm, or any type of mechanical linkage in conjunction with a strain gage or displacement sensor.

Sonar Equipment — Depth sounders and sonar equipment rely extensively on piezoelectric sensors to transmit and receive ultrasonic “pings” in the 50-200kHz range. Besides having an ideal frequency response for such applications, piezoelectric transducers have a high power density that enables large amounts of acoustic power to be transmitted from a small package. For instance, a transducer that is only 4” (100 mm) in diameter may be capable of handling power output greater than 500 watts.

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What are the Uses of Piezoelectric Sensors in Medical Applications?

While piezoelectric sensors are highly valuable to the industrial sector, the industry also makes use of piezoelectric actuators for a variety of applications:

Diesel Fuel Injectors — In the last decade, regulations on emissions from diesel engines have become increasingly stringent. Additionally, customers continue to demand quieter engines with improved power and torque curves. In order to meet these stringent demands for compliance and performance, engine manufacturers have resorted to using precisely timed and metered injections of fuel during the combustion process.

As incredible as this may sound, a single fuel injector may switch fuel flow with pressures exceeding 26,000 psi ( bar) on and off several times in rapid succession during a single power stroke. Such precise control of high-pressure fluid is made possible by using piezoelectric actuators controlling small valves within fuel injectors.

Fast Response Solenoids — Some processes require quick and precise mechanical actuation that is difficult, if not impossible, to achieve with electromagnetic solenoids. While speed may not always be a concern, power consumption or compactness of size is a top priority. In such cases, piezoelectric actuators are often able to fill the niche as they provide fast response and low power consumption in small packages, compared to electromagnetic solenoids.

Optical Adjustment — Some optics need to be adjusted or modulated with a wide frequency response and with a minimum number of moving parts. Piezoelectric actuators are often employed in such applications where they provide fast and accurate control over a long service life:

– The angle of a mirror or diffraction grating may need to be precisely varied according to an electrical input. Such applications are often encountered in optical or physics experiments.

– Earth-based telescope arrays are subject to atmospheric distortion, and spacecraft optics are subject to movement and vibration. In such cases, optics may need to be adjusted (shaped or contoured) in real-time by means of a control system. This will compensate for aberrations that would otherwise impede image resolution.

– Some fiber optic converters rely on piezoelectric actuators to modulate the output of a laser.

Ultrasonic Cleaning — Piezoelectric actuators are also used for ultrasonic cleaning applications. To perform ultrasonic cleaning, objects are immersed in a solvent (water, alcohol, acetone, etc.). A piezoelectric transducer then agitates the solvent. Many objects with inaccessible surfaces can be cleaned using this methodology.

Ultrasonic Welding — Many plastics can be joined together using a process known as ultrasonic welding. This type of process requires ultrasonic waves to be transmitted to a focused area where they can cause pieces of plastic to fuse together. Frequently, piezoelectric actuators are used to accomplish this task.

Piezoelectric Motors — One advantage of using piezoelectric materials is that their characteristics are precise and predictable. Thus, expansion and contraction of a piezoelectric actuator can be precisely controlled as long as the supply voltage is controlled. Some motor designs take advantage of this fact by using piezoelectric elements to move a rotor or linear element in precise increments. Precision on the order of nanometers can be achieved with some piezo motor designs. Piezo motors work at a wide range of frequencies but typically work best in a low frequency range.

In addition to their inherent precision, piezoelectric motors can be used in environments with strong magnetic fields or cryogenic temperatures — environments where conventional motors are unlikely to work. These unique challenges are present in NMRI machines, particle accelerators, and other similar environments.

Stack Actuators — Multiple piezoelectric elements may be stacked to multiply the displacement achieved for a given voltage. These types of devices are known as stack actuators, and they are employed in a variety of specialty applications. Compared to conventional electromagnetic actuators, stack actuators have the following unique advantages:

They can function at cryogenic temperatures or in environments with strong magnetic fields.
They can produce a large amount of force in a small package
They can respond almost instantly to input with high rates of acceleration.
They can achieve extremely high degrees of precision.
They only consume power when work is actually being performed.

These actuators find their uses in proportioning valves, electrical relays, optical modulation, vibration dampening, and other applications requiring fast or precise control of movement.

Stripe Actuators — Two strips of piezoelectric material may be sandwiched together in a configuration that is similar to a bimetallic strip. In this configuration, the electric input causes one strip to expand while the other strip simultaneously contracts, causing a deflection.

Piezoelectric Relays — Piezoelectric elements may be implemented to actuate electromechanical relays or switches. For these applications, either stripe actuators or stack actuators may be used to open and close electrical contacts. Such devices are maintenance-free and last through many cycles without noticeable wear. As an additional benefit, using piezoelectric actuators to operate electrical contacts enables fast and precise control in small packages that are either difficult or impossible to achieve with electromagnetic relays.

What are the Uses of Piezoelectric Sensors in Medical Applications?

Take a look at how the medical field also implements piezoelectric sensors for a variety of day-to-day applications:

Ultrasound Imaging — Piezoelectric transducers are often used in medical ultrasound equipment. Advances in equipment over the decades have enabled improved monitoring of pregnancies and facilitated minimally invasive surgical procedures.

Ultrasonic Procedures — Some non-invasive medical procedures rely on the use of focused ultrasonic waves to break up kidney stones or destroy malignant tissue. Additionally, the advent of the harmonic scalpel has enabled surgeons to simultaneously incise and coagulate tissue during a surgical procedure without the need for cauterization. This leads to less tissue damage, less blood loss, and faster healing times.

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What are the Uses of Piezoelectric Actuators in Consumer Electronics?

What about consumer electronics and technology that is sold in stores throughout the country? Unknown to many consumers, piezoelectric actuators are used in electronics everywhere:

Piezoelectric Printers — Generally speaking, there are two main types of printers that use piezoelectric actuators:

– a dot-matrix printer — In a piezoelectric dot matrix printer, piezoelectric actuators in the printer head move needle-like pins that “poke” through a strip of ink tape (similar to a typewriter) against a piece of paper in various patterns to form characters. For most applications, the use of dot-matrix printers has been superseded by other technologies. However, a dot-matrix printer is the only printer technology capable of generating duplicate and triplicate carbon-copy printouts.

– inkjet printer — In a piezoelectric inkjet printer, piezoelectric actuators in the printer head act on small diaphragms or otherwise change the geometry of an inkwell so that ink droplets are forced out of an orifice onto paper. This is one of the dominant technologies in the printer market to date.

Piezoelectric Speakers — Piezoelectric speakers are featured in virtually every application that needs to efficiently produce sound from a small electronic gadget. These types of speakers are usually inexpensive and require little power to produce relatively large sound volumes. Thus, piezoelectric speakers are often found in devices such as the following:

Cell phones
Ear buds
Sound-producing toys
Musical greeting cards
Musical balloons

Piezoelectric Buzzers — Piezoelectric buzzers are similar to piezoelectric speakers, but they are usually designed with lower fidelity to produce a louder volume over a narrower frequency range. Buzzers are used in a seemingly endless array of electronic devices, including:

Piezoelectric Humidifiers — Many cool mist humidifiers use a piezoelectric transducer to transmit ultrasonic sound energy into a pool of water. The ultrasonic vibrations cause fine water droplets to break away and atomize from the surface of the pool where they become entrained in an air stream and enter the desired space.

Electronic Toothbrushes — Linear piezoelectric actuators are implemented to vibrate the bristles in some electronic toothbrushes.

Piezoelectric Materials for Musical Applications

Aside from technological and industrial applications, piezoelectricity also benefits the arts. There are a variety of musical applications that use piezoelectricity:

Instrument Pickups — Many acoustic-electric stringed instruments utilize piezoelectric pickups to convert acoustic vibrations to electric signals. Typically, a strip of piezoelectric material is placed between the instrument body and a structure that supports the strings. For instance, an acoustic-electric guitar usually houses its piezoelectric strip beneath the bridge and within the saddle. As the strings vibrate, the strip is agitated to generate an electric signal. Electric pickups on violins, violas, and cellos use the same concept, but the piezoelectric pickup may be clamped to the bridge or integrated within the bridge — instead of being located between the bridge and the instrument body.

Microphones — Some microphones (such as contact microphones for percussion instruments) use piezoelectric materials to convert sound vibrations to an electrical output. These microphones generally possess high output impedances that must be matched when designing their respective pre-amplifiers.

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Using Piezoelectricity in Other Applications

Do you have an application that wasn’t listed on the list? Are you wondering if you can use piezoelectricity? The following uses of piezoelectricity represent other options for your industry:

Piezoelectric Ignitors — This is, perhaps, the most well-known and ubiquitous use of piezoelectricity. In a piezoelectric igniter, a button or trigger is used to cock and release a spring-loaded hammer, and the hammer is used to strike a rod shaped piezoelectric ceramic. The sudden mechanical shock to the piezoelectric ceramic produces a rapid rise in voltage that is high enough to jump a sizeable spark gap and ignite fuel. Piezoelectric igniters are commonly used for butane lighters, gas grills, gas stoves, blowtorches, and improvised potato cannons.

Electricity Generation — Some applications require the harvesting of energy from pressure changes, vibrations, or mechanical impulses. The harvesting of energy is possible by using piezoelectric materials to convert deflections or displacements into electrical energy that can either be used or stored for later use.

Microelectronic Mechanical Systems (MEMS) — MEMS devices have become more commonplace as more integrated capabilities are required in smaller packages, such as cell phones, tablet computers, etc. The advantage of MEMS devices is that gyroscopes, accelerometers, and inertial measuring devices can be integrated into chip-sized packages. In order to accomplish such a feat, piezoelectric actuators and sensors are often used.

Tennis Racquets — A somewhat unusual application for piezoelectricity integrates piezoelectric fibers into the throat of a tennis racquet along with a microcontroller in the handle. When the tennis player strikes the ball, the racquet frame deflects and generates an electric output that is boosted, reversed, and fed back into the fibers. This is an attempt to cause destructive interference and dampen structural vibration.

Using Piezoelectricity in Defense Applications

If you’re a part of the defense industry, you can use piezoelectricity for a variety of applications:

Micro Robotics — In the field of small robotics, small power-efficient mechanical actuators and sensors are needed. With the use of piezoelectric actuators, building something as small as a robotic fly that can crawl and fly is technically feasible. In fact, a new field of robotic technology known as Micro Air Vehicles aims to build small drones the size of insects or birds that fly using flapping wings. They control surfaces just as birds and insects do. These types of feats in miniaturization are possible, in part, by using piezoelectric actuators.

Course-changing Bullets — Recently, DARPA invented a .50-caliber bullet that can change course in mid-flight. As absurd as this innovation may sound to some readers, the bullet uses an optical sensor that is mounted on its nose in conjunction with a control system and moveable tail fins to steer itself toward a laser-illuminated target. Although DARPA has not revealed much about their Extreme Accuracy Tasked Ordinance (EXACTO) bullet, the most likely means of manipulating the tail fins probably involves piezoelectric actuators.

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What are the challenges in sourcing reliable piezoelectric materials?

Sourcing reliable piezoelectric materials can be challenging due to the variability in their properties when sourced from different manufacturers. Additionally, the difficulty in ensuring consistent quality and performance across batches complicates the selection process. APC International is a top producer of high quality piezo products. Our processing capabilities include: designing, machining, pressing, firing, custom electroding, poling and testing piezoelectric ceramics and devices. We also have our ISO certification.

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If you wish to explore the world of using piezoelectricity or learn more about what APC International can offer, take a look at our product and service offerings. Contact our team with any questions or visit our knowledge center today.

Piezoelectricity and Its Applications - IntechOpen