Piezo electric effects

The working electrode, in the form of a rectangle of thin foil, c. 20 pm thick, is glued to a piezo-electric ceramic element of the same lateral dimensions. Both the piezo element and the edge of the working electrode arc then isolated from the electrolyte with inert epoxy cement. The essence of the piezo-electric effect is that if the ceramic element is deformed in any way, a... 

Note 4 The flexo-electric effect is the analogue of the piezo-electric effect in solids, where the polarization is induced by a strain that produces a translational deformation of the crystal. The flexo-electric effect in a liquid crystal is caused by a purely orientational deformation. 

The piezo-electric effect of deformations of quartz under alternating current (at a frequency in the order of 10 MHz) is used by coating the crystal with a selectively binding substance, e. g. an antibody. When exposed to the antigen, an antibody-antigen complex will be formed on the surface and shift the resonance frequency of the crystal proportionally to the mass increment which is, in turn, proportional to the antigen concentration. A similar approach is used with surface acoustic wave detectors [142] or with the surface plasmon resonance technology (BIAcore, Pharmacia). 

Contrary to the (non-linear) converse piezo-electric effect v hen pressure is exerted upon a piezo material a voltage is generated - this is called the (linear) piezoelectric effect. 

Ultrasonic nebulizers may divide into the liquid couplet and vertical crystal systems. Ultrasound is produced by the piezo-electric effect on certain crystals. The crystal vibrations are then transmitted to the solution to be nebulized. 

PROPERTIES OF ROCHEUE SALT RELATED TO THE PIEZO-ELECTRIC EFFECT. 

Piezo-electric effect n. The phenomenon exhibited by certain crystals of expansion along one axis and contraction along another when subjected to an electric field. Conversely, compression of certain crystals, generate an electrostatic voltage across the crystal. Piezoelectricity is only possible in crystal classes, which do not possess a center of symmetry. Weast RC (ed) (1971) Handbook of chemistry and physics, 52nd edn. CRC Press, Boca Raton, FL. 

Valasek J (1922b) Properties of Rochelle salt related to the piezo-electric effect. Phys Rev 20 ... 

Pyroelectricity. A sudden modification of the environmental temperature of the crystal (or ceramic) causes a modification in the length (thermal expansion) of the crystal axis whose direction matches with the polarization direction. Due to the piezo electric effect charging occurs. However, the permanent polarization changes with the temperature as the dipole moments in piezoelectric materials depends on the temperature. 

The phenomenon which is described by the third degree tensor d.ji is called piezo-electric effect and it is manifested, for instance, by many quartz crystals, tourmaline with the following formula (Na,Ca) (Al,Fe,Li,Mg)3Alg(B03)3(Sig0j3) and others. 

Motion is generated hy the piezo-electric effect in certain crystalline materials (for instance Quartz), ceramics such as PZT - Pb(ZrTi)03, and polymers (Polyvinyli-dene fluoride - PVDF). In addition, thin films with piezo-electric properties such as Aluminum Nitride (AIN)... 

W. NitsdK and R. Thunker. Applkaiion of the piezo-electric effect in measuring the arterial pressure pulse. Fermelectrics J81 (1987X... 

If the combination of X-ray and morphological evidence does not determine the space-group uniquely, additional information may be sought by tests for piezo-electric and pyro-electric properties, and by an optical examination for any evidence of rotation of the plane of polarization. (See Chapter VIII.) The results of such tests may settle the matter, since only certain crystal classes have these properties. Only positive results are decisive the apparent absence of piezo-electric or pyro-electric effects may be due to feeble phenomena. 

Mechanical Photo-elastic effect Conservation of moment Friction heat Piezo- electricity Magnetostriction Pressure-induced explosion... 

Another common switch, based on the acousto-optic effect, is sketched in Fig. 18. A piezo-electric transducer... 

Moreover, for the piezo- and pyro-electric effect, the physical nature (i. e., the appearance at the spatial ends of the system in focus, and so also for any crystal, of the opposite electric charges) is cancelled by any structure containing the inversion center, because its presence by the inversion of any pair of ends of the structure re-neutralizes it. Therefore, the appearance of such kinds of effects do not clearly indicate the crystallographic class (group), while existing 21 crystallographic groups without an inversion center, as shown in Table 2.11 (see also Table 2.8 for the presence of the symmetry elements and operations). 

The existence or nonexistence of mirror symmetry plays an important role in nature. The lack of mirror symmetry, called chirality, can be found in systems of all length scales, from elementary particles to macroscopic systems. Due to the collective behavior of the molecules in liquid crystals, molecular chirality has a particularly remarkable influence on the macroscopic physical properties of these systems. Probably, even the flrst observations of thermotropic liquid crystals by Planer (1861) and Reinitzer (1888) were due to the conspicuous selective reflection of the helical structure that occurs in chiral liquid crystals. Many physical properties of liquid crystals depend on chirality, e.g., certain linear and nonlinear optical properties, the occurrence of ferro-, ferri-, antiferro- and piezo-electric behavior, the electroclinic effect, and even the appearance of new phases. In addition, the majority of optical applications of liquid crystals is due to chiral structures, namely the ther-mochromic effect of cholesteric liquid crystals, the rotation of the plane of polarization in twisted nematic liquid crystal displays, and the ferroelectric and antiferroelectric switching of smectic liquid crystals. 

Brandenberg SJ, Bellana N, Shantz T (2010) Shear wave velocity as function of standard penetration test resistance and vertical effective stress at California bridge sites. Soil Dyn Earthq Eng 30 1026-1035 Brignoli EG, Gotti M, Stokoe KH (1996) Measurement of shear waves in laboratory specimens by means of piezo-electric transducers. Geotech Test J 19(4) 384-397... 

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