What do cell phones, diesel fuel injectors, acoustic guitar pickups and grill igniters all share in common? All employ piezoelectric material to generate sound or detect vibrations. When stimulated with out-of-plane mode frequencies, a properly sized piezoelectric disc vibrates freely in its natural modes radially. This phenomenon, called frequency conversion, has been studied through simulation and experiments.
Characteristics
A piezoelectric disc is a flat ceramic piece with one or two active layers that produces mechanical or electrical output, acting as either vibration sensors for environmental disturbances, microphones for recording sound waves or compact actuators like linear and rotary motors found in printers as well as high precision mass measurement in microfluidic or lab-on-chip devices.
The principle behind piezoelectric discs is straightforward – when current passes through them, a metal diaphragm bends and expands, producing voltage across the piezoelectric material and creating an electric charge across it. As this happens, surrounding materials vibrate generating soundwaves that can either be detected directly at the disc surface, or through travel distance to be measured using transducers.
Recent research on piezoelectric single crystals has led to greater understanding of their properties. A team led by Dr. Robert Brusa from University of Michigan employed temperature-variable birefringence imaging and piezo-response force microscopy techniques to examine domain structures of tetragonal BS-PT crystals up to 500 degC using temperature variable birefringence imaging and piezo-response force microscopy to characterize them using temperature variable birefringence imaging and piezoresponse force microscopy techniques; they found their morphologies change with temperature from tetragonal symmetry to cubic symmetry which enabled better understanding of temperature effects on piezoelectric response.
Applications
Piezoelectric discs are integral parts of many devices, converting mechanical energy to electric signals for applications including force sensing, vibration control and structural monitoring.
Piezoelectric materials respond to mechanical strain by producing electric current due to their crystalline structures, which when converted into an electrical signal can produce voltage, which can then be measured using electrodes on its surface – this voltage being proportional to how much mechanical stress was applied on that element.
Pizoelectric discs’ unique capacity to convert mechanical energy to electricity makes them ideal for energy harvesting applications. Vibrations or mechanical stress can cause vibration-activated piezoelectric discs to produce small amounts of electrical power that can then be harnessed for low-powered electronic devices that need external power sources.
Piezoelectric sensors can be adapted to suit a range of applications, from medical devices to musical instruments. Their high durability and wide operating frequency range make them suitable for use in harsh environments like factories. Piezoelectric sensors are often employed in manufacturing environments for precise motion and vibration control and non-destructive testing of materials and structures, with airbags and smoke detectors as examples; additionally they’re often employed for sound generating devices such as landline phone ringers and vibration-based keyless entry systems being among other uses.
Materials
piezoelectric disc consists of stacks of piezoelectric ceramic elements bonded together. Its electrodes are often coated in silver plating; standard electrode patterns include wrap-around, side tab and insulation band but others may be implemented upon request. Both its metallization and mechanical tolerances are tested according to customer specifications or internal procedures for testing purposes.
United States Piezoceramic development began during World War II with an eye toward patenting profitable material innovations; in Japan however, scientists quickly developed materials with greater sensitivity than quartz crystal and superior temperature stability that competed well against similar American materials without costly patent restrictions.
Fine PZT powders are mixed with an organic binder to form structural elements of desired shapes (discs, rods and plates) before being heated according to a set time and temperature schedule in order to sinter their particles into dense crystal structures. After cooling off they are then trimmed down in size before their electrodes are attached onto their surfaces.
Piezoelectric discs produce electric current when subjected to mechanical stress such as tapping, squeezing or bending, which can then be converted to useful output through an appropriate circuit. This simple device offers students a fun and educational way to learn electromechanical coupling principles as well as piezoelectricity – as well as providing an introduction into electricity, circuitry and sound generation concepts.
Design
Pizoelectric materials respond to mechanical stress by producing an electrical potential proportional to its deformation, which is then converted to mechanical displacement by applying voltage; this mechanical force can then be utilized in numerous applications like actuation and vibration measurement.
Piezoelectric materials can generally be divided into two broad categories: soft and hard. Harder types like PZT4 offer superior performance over soft materials like polymers such as PVDF and P(VDF-TrFE), which include these polymers. When selecting materials based on electrical properties, piezoelectric stress constant, cost and more.
A radial contour mode disk resonator is an example of an MEMS device which utilizes piezoelectric disc. In its design, the piezoceramics are placed parallel with each other with electrodes interspersed throughout to produce high frequency selectivity for any given frequency. Furthermore, electrodes should be designed so as to prevent accidental contact between external objects and piezoceramics which could damage them.
One way to enhance selectivity is through design that centers the piezoceramics at the transducer node instead of offsetting them behind it. This provides optimal electromechanical coupling between energy input and vibrational output of piezoceramics; further, this reduces prestress transfer across them.