Piezoelectric and Ferroelectric Properties

Shearing forces exerted on an ionic crystal (left) result in cleavage (right) 

Metals behave differently since the metal atoms are embedded in an electron gas. The attractive forces remain active even after mutual displacement of parts of a crystal has occurred. Metals therefore can be deformed without fracture. 

Explanation of the piezoelectric effect external pressure causes the deformation of a coordination tetrahedron, resulting in a shift of the centers of gravity of the electric charges 

Crystals can only be piezoelectric when they are non-centrosymmetric. In addition, they may not belong to the crystal class 4 32. The effect is thus restricted to 20 out of the 32 crystal classes. 

In some crystalline substances the centers of gravity of positive and negative charges do not coincide in the first place, i.e. permanent dipoles are present. Concerning the electrical properties, the following cases can be distinguished. 

Structure, then for every tetrahedron there is another tetrahedron which has the exact opposite orientation the electric fields of the dipoles compensate each other. If, however, all tetrahedra have the same orientation or some other mutual orientation that does not allow for a compensation, then the action of all dipoles adds up and the whole crystal becomes a dipole. Two opposite faces of the crystal develop opposite electric charges. Depending on the direction of the acting force, the faces being charged are either the two faces experiencing the pressure (longitudinal effect) or two other faces in a perpendicular or an inclined direction (transversal effect). 

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Potassium Phosphates. The K2O—P20 —H2O system parallels the sodium system in many respects. In addition to the three simple phosphate salts obtained by successive replacement of the protons of phosphoric acid by potassium ions, the system contains a number of crystalline hydrates and double salts (Table 7). Monopotassium phosphate (MKP), known only as the anhydrous salt, is the least soluble of the potassium orthophosphates. Monopotassium phosphate has been studied extensively owing to its piezoelectric and ferroelectric properties (see Ferroelectrics). At ordinary temperatures, KH2PO4 is so far above its Curie point as to give piezoelectric effects in which the emf is proportional to the distorting force. There is virtually no hysteresis. 

Alkaline-Earth Titanates. Some physical properties of representative alkaline-earth titanates ate Hsted in Table 15. The most important apphcations of these titanates are in the manufacture of electronic components (109). The most important member of the class is barium titanate, BaTi03, which owes its significance to its exceptionally high dielectric constant and its piezoelectric and ferroelectric properties. Further, because barium titanate easily forms solid solutions with strontium titanate, lead titanate, zirconium oxide, and tin oxide, the electrical properties can be modified within wide limits. Barium titanate may be made by, eg, cocalcination of barium carbonate and titanium dioxide at ca 1200°C. With the exception of Ba2Ti04, barium orthotitanate, titanates do not contain discrete TiO ions but ate mixed oxides. Ba2Ti04 has the P-K SO stmcture in which distorted tetrahedral TiO ions occur. 

Hattori, X, Takahashi, Y, lijima, M., Fukada, E., 1996. Piezoelectric and ferroelectric properties of polyurea-5 thin films prepared by vapor deposition polymerization. J. Appl. Phys. 79,1713-1721. 

Barium titanate is a crystalline ceramic compound with outstanding diaelectric, piezoelectric, and ferroelectric properties. It is used in capacitors and as a piezoelectric transducer. 

Barium Titanate. BaTi03, m.p. 1618°C. Made by heating a mixture of barium carbonate and titania at 1300-1350°C. Because of its high dielectric constant (1350-1600 at 1 MHz and 25 C) and its piezoelectric and ferroelectric properties, it finds use in electronic components its Curie temperature is 120-140°C. The properties can be altered by the... 

Piezoelectric and Ferroelectric Properties of Ln2Tl207 Thin Films... 

Piezoelectric and Ferroelectric Properties ofLn2Tifij Thin Films 1245... 

Piezoelectric and Ferroelectric Properties ofLn2Tij0j Thin Films 247... 

Johnson J.A., Lisoni J.G., Wonters D.J. Iridium based electrodes for ferroelectric capacitor fabrication. Mater. Res. Soc. Symp. Proc. 2002 688 59-64 Kang J., Yoko T., Kozuka H., Sakka S. Preparation of Pb-based complex perovskite coating films by sol-gel method. In Sol-Gel Optics, vol. II, J.D. Mackenzie, ed. Pfoc. SPIE 1992 1758 249-259 Kim Dong-Joo, Maria Jon-Paul, Kingon A.I. Compositional effect on the piezoelectric and ferroelectric properties of chemical deposited PZT thin films. Mater. Res. Soc. Symp. Proc. 2002 688 351-356... 

Galetti P et al (eds) (1988) Piezoelectric and ferroelectric properties of P(VDF-TrFE) copolymers and their pUcation to ultrasonic transducers. In Medical apphcations of piezoelectric polymers gordon and breach. New York... 

The controlled deformation of the EAPs is greatly dependent on the distribution of its piezoelectric and ferroelectric properties. The lateral homogeneity of these properties is of particular high importance. Visualization of these lateral distributions is possible via imaging of the local piezoelectric and pyroelectric activity. 

BARIUM TITANATE. BaTiOj M.p. >1500°C. Pure form undergoes abrupt phase change from tetragonal to cubic at 130°C, the Curie temperature. Barium titanate is usually produced by the solid-state reaction of barium carbonate and titanium dioxide. Has widespread use in the electronics industry because of its high dielectric constant, and piezoelectric and ferroelectric properties. The high dielectric constant of BaTiOj and the ease with which its electrical properties can be modified by combination with other materials make it exceptionally suitable for miniature capacitors. 

K. Koga, N. Minoto, and R OhigatU. Oamposilioa dependence of Piezoelectric and ferroelectric properties of vinylidene fluoridc-trifluatoethyleoe copalymeta, 7 o7yiner /pn. 54.-9S3 (1985). 

Fu DW, Zhang W, Xiong RG (2008) The first metal-organic framework (MOF) of imazethapyr and its SHG, piezoelectric and ferroelectric properties. Dalton Trans 3946-3948... 

Microorganisms that are efficient in producing AMV are cellular factories for this 5-carbon monomer, which is a polyamide building block. The AMV monomer is a precursor of valero-lactam, which is important for nylon-5 homopolymer synthesis. This would drive the biopolyamide and biopolymer fields. The polymers, nylon-4,5 and nylon-5,5, can be produced by the polymerization of glutarate with putrescine and cadaverine, respectively. These polymers have additional piezoelectric and ferroelectric properties that are useful in sensors and electronics. 

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