Quartz, piezo-electric, properties

Alpha-quartz has many useful properties which lead to its wide use in industry as a glass, ceramic and molecular sieve. However, undoubtedly its most technically important use occurs by virtue of its piezo-electric properties, which allow it to be used as a frequency regulating device in satellites, computers, and the ubiquitous quartz-watch . Unfortunately, it has been found that quartz crystals are susceptible to damage by radiation, and that this is associated with the presence of defects in the crystal lattice. These defects, particularly aluminum and hydrogen, are grown into the crystal and so far have proved impossible to remove. This problem has been the cause of intensive research, which has led to some information on the possible types of defects involved, but has failed to produce details of their geometries, and the way in which they interact. 

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)... 

The quartz crystal microbalance is based on the piezo-electric properties of quartz, characterized by two complementary phenomena (i) When force is applied to a quartz crystal changing its dimensions, a potential difference is generated across it (ii) When a potential is applied across it, its dimensions are changed. When the potential applied is a periodic signal (typically a sine wave) the crystal vibrates at the frequency of the applied signal. This property is the physical basis for the quartz crystal microbalance (QCM). 

Mason WP (ed) (1964) Physical acoustics. Academic, New York, NY Nelson DF (1979) Electric, optic and acoustic interactions in dielectrics. Wiley, New York, NY Thomson W (Lord Kelvin) (1878) On the piezoelectric property of quartz. Phil Mag 5 4 Tichy J, Gautschi G (1980) Piezoelektrische Messtechnik. Springer, Heidelberg Toledano P, Dmitriev V (1996) Reconstructive phase transitions. World Scientific, Singapore Valasek J (1920) Piezoelectric and allied phenomena in Rochelle salt. Phys Rev 15 537-538 Valasek J (1921) Piezoelectricity and allied phenomena in Rochelle salt. Phys Rev 17 475-481 Valasek J (1922) Piezo-electric activity of Rochelle salt under various conditions. Phys Rev 19 478 Valasek J (1924) Dielectric anomalies in Rochelle salt crystals. Phys Rev 24 560 Voigt W (1890) General theory of the piezo- and pyroelectric properties of crystals. Abh Gott 36 1-99... 

Any type of acoustic transducer, such as quartz crystal microbalance (QCM) or surface acoustic wave device (SAW), is fundamentally based on the piezoelectric effect. This was first described in 1880 by Jacques and Pierre Curie as a property of crystalline materials that do not have an inversion centre. When such a material is subjected to physical stress, a measurable voltage occurs on the crystal surfaces. Naturally, the opposite effect can also be observed, i.e. applying an electrical charge on a piezoelectric material leads to mechanical distortion, the so-called inverse piezo effect. These phenomena can be used to transfrom an electrical signal to a mechanical one and back, which actually happens in QCM and SAW. Different materials are ap-pHed for device fabrication, such as quartz, Hthium tantalate, lithium titanate... 

Certain crystals, such as quartz, feature a physical relationship between mechanical force and electric charge. When the crystal lattice ions are elastically shifted relative to one another due to an external force, an electric polarization can be detected by means of metallic electrodes on the surface. This so-called piezoelectric effect was first scientifically explained by the brothers Jacques and Pierre Curie in 1880 and forms the basis for piezo sensors (see Sect. 7.3). The effect is reversible and is then called reciprocal or inverse piezoelectric effect. If, for instance, an electric voltage is applied to a disc shaped piezo crystal, the thickness of the crystal changes due to the reciprocal piezoelectric effect. It is this property that is made use of in actuators. 

---