Piezoelectric effect is the effect of polarization of a dielectric under the influence of mechanical
With the direct piezoelectric effect, deformationof a piezoelectric sample leads to the appearance of an electric voltage between the surfaces of a deformable solid; in the case of the inverse piezoelectric effect, the application of a voltage to the body causes its deformation.
What are piezoelectric materials?
Piezoelectric materials are materials that have the ability to generate an internal electrical charge from applied mechanical stress.
Certain naturally occurring substances exhibit a piezoelectric effect. These include:
- Bone,
- Crystals,
- Certain ceramics,
- DNA,
- Enamel,
- Silk,
- Dentin and more.
Materials that demonstratethe piezoelectric effect also exhibits the inverse piezoelectric effect (also called inverse or inverse piezoelectric effect). The inverse piezoelectric effect is the internal generation of mechanical stress in response to an applied electric field.
History of piezoelectric materials
Crystals were the first material usedin early experiments with piezoelectricity. The Curie brothers, Pierre and Jacques, first proved the direct piezoelectric effect in 1880. Scientists have expanded their practical knowledge of crystal structures and pyroelectric materials (materials that generate an electrical charge in response to temperature changes).
They measured the surface charges of the following specific crystals, namely:
- Cane sugar
- Tourmaline,
- Quartz,
- Topaz,
- Rochelle's salt (sodium-potassium salt of tartaric acid),
As a result, it was quartz and Rochelle's salt that demonstrated the highest piezoelectric effects.
However, the Curie brothers did not predict otherwise.piezoelectric effect. It was mathematically derived by Gabriel Lippmann in 1881. Curie then confirmed the effect and provided quantitative evidence for the reversibility of electrical, elastic, and mechanical deformations in piezoelectric crystals.
By 1910, there were 20 classes of natural crystals, inin which the piezoelectric effect is observed were fully determined and published in Lehrbuch Der Kristallphysik - «Textbook of Crystal Physics». But it remained a little-known and high-tech niche area of physics with no apparent technological or commercial applications.
Until the war came.
World War
First technological applicationpiezoelectric material was used as an ultrasonic submarine detector. The plastic detector is made of a transducer (a device that converts one type of energy into another) and a hydrophone. The transducer is made of thin quartz crystals glued between two steel plates.
The huge success of the ultrasonic detectorsubmarines during the war stimulated the intensive technological development of piezoelectric devices. After World War I, piezoelectric ceramics were used in phonograph cartridges.
The Second World War
The use of piezoelectric materials advanced significantly during World War II due to independent research by Japan, the USSR and the United States.
In particular, advances in understanding the relationshipbetween crystal structure and electromechanical activity along with other advances in research have completely changed the approach to piezoelectric technology. For the first time, engineers were able to manipulate piezoelectric materials for a specific device application, instead of observing the properties of the materials and then looking for suitable uses of the observed properties.
This development allowed the creation of manywar-related applications of piezoelectric materials such as ultra-sensitive microphones, high-power sonar devices, sonar buoys (small buoys with the ability to listen to a hydrophone and radio transmission to monitor the movement of ocean-going vessels) and piezo ignition systems for single-cylinder ignition.
Piezoelectric crystals - what are they?
Below is an incomplete listpiezoelectric crystals with some brief descriptions of their use. We will discuss some specific applications of the most commonly used piezoelectric materials later.
Naturally occurring crystals:
- Quartz is a stable crystal used in clock crystals and frequency reference crystals for radio transmitters,
- Sucrose (table sugar)
- Rochelle salt - produces a lot of tension with compression; used in early crystal microphones.
- Topaz,
- Tourmaline,
- Berlinite (AlPO₄.) — a rare phosphate mineral structurally identical to quartz.
Technogenic crystals- Gallium orthophosphate (GaPO₄), an analogue of quartz and langasite, an analogue of quartz.
Piezoelectric ceramics:
- Barium titanate (BaTiO₃). The first piezoelectric ceramic is discovered.
- Lead titanate (PbTiO₃)
- Lead Zirconate Titanate (PZT)
- Potassium niobate (KNbO₃)
- Lithium niobate (LiNbO₃)
- Lithium tantalate (LiTaO₃)
- Sodium tungstate (Na₂WO₄)
Lead-free piezo ceramics:
The following materials were developed in response to concerns about the harmful effects of lead on the environment.
- Sodium potassium niobate (NaKNb). This material has properties similar to PZT.
- Bismuth ferrite (BiFeO₃)
- Sodium niobate (NaNbO₃)
Biological piezoelectric materials:
- Tendon
- Wood
- Silk
- Enamel
- Dentine
- Collagen
Applications of piezoelectric materials
Piezoelectric materials are used in many industries, including:
- Production
- Medical equipment
- Telecommunications
- Automotive industry
- Information Technology (IT)
High voltage power supplies:
- Electric lighters.When you press the button on the lighter, the button causes a small, spring-loaded hammer to hit the piezoelectric crystal, creating a high voltage current that flows through the gap to heat and ignite the gas.
- Gas grills or stoves and gas burners. They work the same way as lighters, but on a larger scale.
- Piezoelectric transducer. It is used as an AC voltage multiplier in cold cathode fluorescent lamps.
Piezoelectric sensors
Ultrasonic transducers are used ineveryday medical imaging. The transducer is a piezoelectric device that acts as both a sensor and an actuator. Ultrasonic transducers contain a piezoelectric element that converts an electrical signal into mechanical vibration (transmission mode or drive components) and mechanical vibration into an electrical signal (reception mode or sensor component).
The piezoelectric element is usually cut to 1/2 the desired wavelength of the ultrasonic transducer.
Other types of piezoelectric sensors include:
- Piezoelectric microphones.
- Piezo pickups for electro-acoustic guitars.
- Sonar waves. Sound waves are generated and received by a piezoelectric element.
- Electronic drum pads. The elements detect the impact of drummers' sticks on the pads.
- Medical acceleromyography.This is used when a person is under anesthesia and injected with muscle relaxants. The piezoelectric element in the acceleromyograph determines the force that occurs in the muscle after nerve stimulation.
Piezoelectric Actuators
One of the advantages of piezoelectric actuatorsis that the high voltage of the electric field corresponds to tiny micrometer changes in the width of the piezoelectric crystal. These micro-masses make piezoelectric crystals useful as actuators when precise positioning of tiny objects is required, such as in the following devices:
- Loudspeakers
- Piezoelectric motors
- Laser electronics
- Inkjet printers (crystals control the release of ink from the print head onto the paper)
- Diesel Engines
- X-ray shutters
Smart materials
Smart materials are a wide class of materials,whose properties can be changed in a controlled manner by external influences such as pH, temperature, chemicals, applied magnetic or electric field or voltage.
Piezoelectric materials comply with thisdefinition, because an applied voltage creates a voltage in the piezoelectric material, and conversely, the application of an external voltage also produces electricity in the material.
Additional intellectual materialsinclude shape memory alloys, halochromic materials, magnetocaloric materials, thermosensitive polymers, photovoltaic materials, and many others.
What does the future hold for piezoelectric materials?
So what's next for piezoelectric materials?future? It is an exciting idea that piezoelectric nanofiber materials could be commercially used as an energy source. They rely on mechanical force to generate electricity. Therefore, if you place them, for example, on a touch screen, they can act as a device charger. Of course, some of the power created goes towards performing the action on the touch screen. But there is an option to create additional resources.
The two most popular materials used for nanogenerators are polymer polyvinylidene fluoride(PVDF)and ceramic Lead Zirconate Titanate (PZT). PVDF demonstrates higherpiezoelectric properties than other polymers. This is due to its polar crystal structure. PZT, on the other hand, also has a crystalline structure and is capable of generating much higher voltages than other piezoelectric energy harvesting materials. It is also mechanically stronger, especially in nanowire form.
Industrial designer Jung-Hoon Kimhas came up withthe brilliant idea of using piezoelectricity to power a car. Such devices, which charge batteries, receive energy from vibrations that occur when the car is moving. This technology does not produce emissions and does not depend on fossil fuels, which makes it environmentally friendly.
Another industrial designer, Paul Frigu,developed a mobile phone that can be charged by itself! The Zeri model uses thermoelectric and piezoelectric systems. The first uses temperature changes to generate charge; the second is air vibrations. These two features make the smartphone 100% environmentally friendly.
Mexican Alberto Villarreal created a pair of shoes,which illuminates the path to its owner. Using the kinetic energy of walking or running, electroluminescent polymers can produce light. These effects will be useful for runners.
The next innovative technology is in the sectortablets. Using regenerative touchscreen input may well be the preferred way to charge these popular gadgets. On average (statistically) the average person taps the touchscreen 1,000 times a day. This is more than enough power to power the tablet.
Finally, perhaps the most interestingpiezoelectric gadget - shower. Designed by Finnish, Mexican and German engineers, it contains many tiny nanowires. These nanowires use the energy of passing water to generate electricity, which is used to heat the water. The device also has touch panels that monitor the amount of water used and count the time the user spends in the shower. There is also a regulator that controls the water pressure.
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Dielectric is a substance that is relatively badconductive electric current. The electrical properties of dielectrics are determined by their ability to polarize in an external electric field. The term was introduced into science by the English physicist M. Faraday. The concentration of free charge carriers in the dielectric does not exceed 10⁸ cm⁻³.