Piezoelectrics devices

By use of a piezoelectric device, as in a gas lighter, a small spark containing electrons and ions can be produced. If the spark is introduced into the gas in a discharge tube, it will provide the extra initial electrons and ions needed to start a continuous discharge. A plasma torch is frequently lit (started) in this fashion. 

Japanese suppHers generally dominate the electronic ceramic business. Japanese production of ferroelectric devices in the first nine months of 1990 was valued at 711 x 10 for ceramic capacitors and 353 x 10 for piezoelectric devices, representing growths of 7 and 10.8%, respectively, over the previous year. 

In an attempt to stimulate onshore production of synthetic quartz and piezoelectric devices in the 1970s, Brazil imposed an embargo on exports and ultimately raised the price several-fold for small quartz crystals used as the starting material for quartz growth. However, sources of suitable pure quartz were located in the United States and Canada, including vein and pegmatic deposits (1). Synthetic processes compatible with the natural U.S. quartz starting material from a variety of sources were developed, and U.S. production became relatively independent of imports (1). 

The deposition temperature range is 300-500°C, the partial pressure of the alkyl is 0.5-2.5 Torr, and that of THF is 20-80 Torr. ZnO has found applications in piezoelectric devices, transducers, coatings for photoconductive devices, and non-linear resistors (varistors), and overvoltage protectors. 

PZT (lead zirconate titanate) and PLZT (lead lanthanum zirconate titanate) combine ferroelectic, optical, and electronic properties and are used in optoelectronic and piezoelectric devices. Powders for hot pressing produced by CVD are being investigated. 

Kymissis et al. have examined the possibility of generation of electrical power parasitically from devices built in a shoe, a wearable subsystem for the soldier. Merits of three different types of piezoelectric devices are compared. They are a unimorph strip piezoceramic composite, a stave of multilayer laminate of PVDF foil, and a shoe-mounted rotary magnetic generator as a part of technology demonstration a piezoelectric embedded shoe has also been postulated to periodically broadcast a digital radio frequency identification (RFID) signal as the wearer walks. 

The n-A curves were measured with a trough equipped with a moving blade and a piezoelectric device (Figure 2). Both the trough (286 mm long and 70 mm wide) and blade were coated with Teflon. The subphase temperature was kept within 0.1 °C by use of a water jacket connected with a thermostated circulation system, and the environmental air temperature was kept at 18 °C. The surface tension was measured with a Wilhelmy plate made of filter paper (25 x 25 x 0.25 mm) using a piezoelectric device. The surface pressure(ji) is defined as ... 

A) piezoelectric device, (B) filter paper(Wilhelmy plate), (C) trough, (D) blade, (E) arms,... 

Piezoelectric biomaterials, 3 748-750 Piezoelectric ceramics, 1 708-710 U.S. market trends, l 710t Piezoelectric coefficient tensor, 11 93, 94 Piezoelectric crystals, 17 423 in acoustic wave sensors, 22 270 Piezoelectric devices, applications of, 11 103-104... 

The scanning tunneling microscope uses an atomically sharp probe tip to map contours of the local density of electronic states on the surface. This is accomplished by monitoring quantum transmission of electrons between the tip and substrate while piezoelectric devices raster the tip relative to the substrate, as shown schematically in Fig. 1 [38]. The remarkable vertical resolution of the device arises from the exponential dependence of the electron tunneling process on the tip-substrate separation, d. In the simplest approximation, the tunneling current, 1, can be simply written in terms of the local density of states (LDOS), ps(z,E), at the Fermi level (E = Ep) of the sample, where V is the bias voltage between the tip and substrate... 

New possibilities exist for the development of piezoelectric devices using so-called 1-3 composites. These consist of an array of piezoelectric pillars embedded in a pliable material providing a transducer in the form of a flexible sheet (Fig. 7.5) which can be moulded to fit the shape of a reactor. A particular advantage of such a system is that the emitting face is a combination of ceramic and plastic and can provide much better acoustic transmission into aqueous systems. 

Zinc oxide occurs in nature as mineral zincite. It is the most important zinc compound and has numerous industrial applications. Zinc oxide is the pigment in white paints. It is used to make enamels, white printing inks, white glue, opaque glasses, rubber products and floor tiles. It is used in cosmetics, soaps, pharmaceuticals, dental cements, storage batteries, electrical equipment, and piezoelectric devices. Other applications are as a flame retardant, as a UV absorber in plastics, and a reagent in analytical chemistry. A major application of zinc oxide is in the preparation of most zinc salts. In medicine, the compound is used as an antiseptic, an astringent and a topical protectant. 

The total mass of particles per unit volume of air is one of the major parameters used to characterize particles in air and, along with size, is the basis of air quality standards for particulate matter (see Chapter 2). Methods of mass measurement include gravimetric methods, /3-ray attenuation, piezoelectric devices, and the oscillating microbalance. 

The quartz crystal microbalance (QCM) is a piezoelectric device consisting of a thin (e.g.) quartz wafer sandwiched between two electrodes. A potential applied across the electrodes results in an oscillation of the quartz. The frequency of the oscillation, which can be measured accurately, is sensitive to mass loading. The relationship between frequency and mass loading is described by the Sauerbray equation ... 

Increasing the concentration of surfactants in water to a level above the CMC leads to the formation of rod-like micelles and, subsequently, liquid crystals [251]. Both liquid crystals and liquid-crystalline polymers [252] have been used as media for small particle generation [253, 254] and have also acted as piezoelectric devices [255]. Of particular interest are metallomesogens, the metal complexes of organic ligands which exhibit liquid crystalline behavior [255],... 

A piezoelectric mass sensor is a device that measures the amount of material adsorbed on its surface by the effect of the adsorbed material on the propagation of acoustic waves. Piezoelectric devices work by converting electrical energy to mechanical energy. There are a number of different piezoelectric mass sensors. Thickness shear mode sensors measure the resonant frequency of a quartz crystal. Surface acoustic wave mode sensors measure the amplitude or time delay. Flexure mode devices measure the resonant frequency of a thin Si3N4 membrane. In shear horizontal acoustic plate mode sensors, the resonant frequency of a quartz crystal is measured. 

The main advantage of piezoelectric devices is that, in principle, any process that results in a mass change at an interface can be measured. However, this very nonselective transduction process is also a major disadvantage in that it mandates the use of even more selective surface chemistries than are required for other types of chemical transducer systems. This will make the implementation of piezoelectric chemical sensing devices for ocean measurements rather difficult, but by no means impossible. Indeed, the coupling of pattern recognition techniques with an array of marginally selective piezoelectric transducers may, in the future, make these devices more useful for quantitative ocean measurements. 

Krause (Ref 16) describes a piezoelectric device, called "carbon piezometer , in which a carbon disc, similar to the one used in telephones, is utilized in lieu of quartz or tourmaline crysts... 

Piezoelectric devices have found a host of other aerospace applications. For example, one of the most troublesome problems faced by airlines is the detection of tiny hairline fractures in an aircraft body. These fractures often appear long before they can be observed visually during routine maintenance procedures. Yet, once they begin to develop, they can quite suddenly and dramatically lead to much larger cracks and failures that result in disastrous accidents. For this reason, airline companies are constantly... 

Piezoelectric detectors are one of the most promising solutions to this problem. They can be installed at various locations on the aircraft body where they can constantly monitor the integrity of the materials of which the body is made. If cracks begin to develop at any location on the body, they can be detected because they result in the formation of small-scale shock waves as air passes over the aircraft body. These shock waves cause minute distortions of the aircraft s surface. While these distortions are too small to he noticed by most ordinary procedures, they are large enough to create electrical signals in nearby piezoelectric devices that can he picked up and analyzed by processing units attached to them. 

A filter is required to pass a certain selected frequency band, or to stop a given band. The passband for a piezoelectric device is proportional to k2, where k is the appropriate coupling coefficient. The very low k value of about 0.1 for quartz only allows it to pass frequency bands of approximately 1% of the resonant frequency. However, the PZT ceramics, with k values of typically about 0.5, can readily pass bands up to approximately 10% of the resonant frequency. Quartz has a very high Qm (about 106) which results in a sharp cut-off to the passband. This, coupled with its very narrow passband, is the reason why the frequency of quartz oscillators is very well defined. In contrast PZT ceramics have Qm values in the range 102—103 and so are unsuited to applications demanding tightly specified frequency characteristics. 

---