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Topic: Pyroelectricity

	Pyroelectricity - Wikipedia, the free encyclopedia
		Pyroelectricity can be visualized as one side of a triangle, where each corner represents energy states in the crystal: kinetic, electrical and thermal energy.
		Passive infrared sensors are often designed around pyroelectric materials, as the heat of a human or animal from several feet away is enough to generate a difference in charge.
		The total pyroelectric coefficient measured at constant stress is the sum of the pyroelectric coefficients at constant strain (primary pyroelectric effect) and the piezoelectric contribution from thermal expansion (secondary pyroelectric effect).
	en.wikipedia.org /wiki/Pyroelectricity (782 words)

	Pyroelectricity
		Pyroelectricity is the electrical potential created in certain materials when they are heated.
		The first reference to the pyroelectric effect is in writings by Theophrast[?] in 314 BC, who noted that tourmaline becomes charged when heated.
		Pierre Curie and his brother, Jacques, studied pyroelectricity in the 1880s, leading to their discovery of some of the mechanisms behind piezoelectricity.
	www.ebroadcast.com.au /lookup/encyclopedia/py/Pyroelectricity.html (278 words)

	Pyroelectricity
		Ačkoli umělý pyroelectric materiály byly připraveny, účinek byl nejprve objeven v nerostech takový jak křemen a tourmaline a jiný ionic krystaly.
		Pyroelectric účinek je také přítomný v obou kost a šlacha.
		Všichni pyroelectric materiály jsou také piezoelectric, dvě vlastnosti být blízko příbuzný.
	wikipedia.infostar.cz /p/py/pyroelectricity.html (285 words)

	Pyroelectricity Article, Pyroelectricity Information (Site not responding. Last check: 2007-10-10)
		Pyroelectricity is the electricalpotential created in certain materials when they are heated.
		Pyroelectricity can be visualized as one side of a triangle, where each corner represents energy states in the crystal:kinetic, electrical and thermal energy.
		Pyroelectricity is definitely not a new concept, but researchand application of the useful property continues to this day.
	www.anoca.org /pyroelectric/effect/pyroelectricity.html (418 words)

	Pyroelectric crystal - Wikipedia, the free encyclopedia
		Pyroelectric crystals are crystals that generate electricity when heated.
		Pyroelectric materials can be used as infrared and millimeter wavelength detectors.
		Ferroelectrics are materials which possess an electric polarization in the absence of an externally applied electric field such that the polarization can be reversed if the electric field is reversed.
	en.wikipedia.org /wiki/Pyroelectric_crystal (749 words)

	Pyroelectric device with coplanar electrodes (Site not responding. Last check: 2007-10-10)
		Pyroelectric devices, according to this invention, combine the advantages of both conventional edge-type and face-type electrodes without some of the disadvantages of either, and the manner in which they are fabricated makes it possible for the first time to obtain high performance inexpensively.
		It is still another object of this invention to provide a pyroelectric device which may be utilized for the fabrication of arrays by depositing a multiplicity of closely-spaced coplanar electrodes on a non-c-face of a pyroelectric material by masking the electrodes to obtain precision of spacing.
		The pyroelectric detectors of this invention are particularly directed to small area devices which are difficult and expensive to fabricate in conventional detector assemblies with c-face electrodes oppositely disposed in c-axis normal faces of a pyroelectric material.
	www.sacnewsmonthly.com /invent/floor_cleaning_machine/pyroelectric_with_coplanar_electrodes.html (4507 words)

	Pyroelectricity Information - Pyroelectricity
		Pyroelectric charge in minerals develops Pyroelectricity on the opposite faces of asymmetric crystals.
		The field of electronics is the study and use of systems that operate by controlling the flow of electrons or other electrically charged particles in devices such as thermionic valves and semiconductors.
		The study of new semiconductor devices and their technology is sometimes considered as a branch of physics.
	www.inanot.com /Ina-Electronics_Topics_Pi_-_Ra-/Pyroelectricity.html (458 words)

	PIEZOCRYST: Advanced Sensorics GmbH - Piezoelectricity - Pyroelectricity
		Two effects contribute to that phenomenon: the primary pyroelectric effect, caused by a change in existing dipole moments in the crystal and the secondary, caused by a change in charge density upon thermal expansion of the material.
		This effect produces confusing aberrations for many industrial applications since pyroelectric "artefacts", that have to be carefully separated, often superimpose the piezoelectric signals of interest.
		Pyroelectricity requires the presence of permanent electric dipoles (whose magnitude is affected as a result of temperature changes).
	www.piezocryst.com /piezoelectricity_pyro.php (472 words)

	Data recording sheet - Patent 4389445
		However, the pyroelectric method of reproducing signals is disadvantageous in that the piezo-electric action caused by variations of tension applied to the sheet may cause noise.
		In the case where the data is reproduced in a piezo-electric mode, the application of pressure must be effectuated perpendicular to the surface of the sheet to detect the difference in polarization between parts of the sheet.
		Pyroelectricity is generated in the polarized part of the tape by scanning the latter with a continuous laser beam low in intensity.
	www.freepatentsonline.com /4389445.html (3031 words)

	Ceramic - New World Encyclopedia Preview
		Thus, pyroelectric materials can be used to interconvert between thermal, mechanical, and electrical forms of energy.
		Such materials are used in motion sensors, where the tiny rise in temperature from a warm body entering a room is enough to produce a measurable voltage in the crystal.
		Pyroelectricity, in turn, is observed most strongly in materials that also display the ferroelectric effect.
	www.newworldencyclopedia.org /preview/Ceramic (2063 words)

	Pyroelectricity
		Pyroelectricity can be visualized as one side of a triangle, where each corner represents energy states in the crystal: kinetic energykinetic, electrical energyelectrical and thermal energythermal energy.
		Passive infrared sensorsMotion detection devices are often designed around pyroelectric materials, as the heat of a human or animal from several feet away is enough to generate a difference in charge.
		Piezoelectric Crystal Classes: 1, 2, m, 222, mm2, 4, -4, 422, 4mm, -42m, 3, 32, 3m, 6, -6, 622, 6mm, -62m, 23, -43m Pyroelectric: 1, 2, m, mm2, 4, 4mm, 3, 3m, 6, 6mm The property of pyroelectricity is the measured change in net polarization (a vector) proportional to a change in temperature.
	www.territoriopc.com /eng/pyroelectricity.php (757 words)

	Piezoelectricity - Wikipedia, the free encyclopedia (via CobWeb/3.1 planetlab2.cs.unc.edu) (Site not responding. Last check: 2007-10-10)
		A related property known as pyroelectricity, the ability of certain mineral crystals to generate electrical charge when heated, was known of as early as the 19th century, and was named by David Brewster in 1824.
		In 1880, the brothers Pierre Curie and Jacques Curie predicted and demonstrated piezoelectricity using tinfoil, glue, wire, magnets, and a jeweler's saw.
		Of the thirty-two crystal classes, twenty-one are non-centrosymmetric (not having a centre of symmetry), and of these, twenty exhibit direct piezoelectricity (the 21st is the cubic class 432).
	en.wikipedia.org.cob-web.org:8888 /wiki/Piezoelectricity (2648 words)

	pyroelectricity - Article and Reference from OnPedia.com
		As a result of a change in temperature, positive and negative charges move to opposite ends through migration, and hence, an electrical potential is established.
		(See Pyroelectric crystals.) The first reference to the pyroelectric effect is in writings by Theophrastus in 314 BC, who noted that tourmaline becomes charged when heated.
		There are applications of piezoelectric fibers in the active fiber reinforced composites that can be used as both sensors and actuators.
	www.onpedia.com /encyclopedia/pyroelectricity (393 words)

	Pyroelectricity: From Ancient Curiosity to Modern Imaging Tool - Physics Today August 2005
		One of the least-known properties of solid materials, pyroelectricity is rigorously defined as the temperature dependence of the spontaneous polarization in certain anisotropic solids.
		To appreciate the meaning of that definition and the nature of the pyroelectric effect, consider a simple example: a thin, parallel-sided sample of material, such as a tourmaline crystal or a ceramic disk of barium titanate, cut so that its crystallographic symmetry axis is perpendicular to the flat surfaces.
		Incorporating thin-film pyroelectrics directly on semiconductor substrates is emerging as an important research area and IR detection and imaging using pyroelectrics is likely to become much more widespread as costs go down.
	www.physicstoday.org /pt/vol-58/iss-8/p31.html (2430 words)

	Ancient Greece: Electricity and Magnetism
		The first reference to the pyroelectric effect is made by Theophrastus in 314 BC, who noted that tourmaline becomes charged when heated.
		Pyroelectricity gave birth to piezoelectricity in 1880, and to ferroelectricity in 1920.
		The field of pyroelectricity flourished in the twentieth century with many applications, particularly in inf rared detection and thermal imaging.
	www.mlahanas.de /Greeks/ElectroMagnet.htm (1124 words)

	Musical instrument and a method of applying a low impedance amplifier to a musical instrument - Patent 5484958
		A musical instrument as defined in claim 4, wherein said sound source structure is each of strings of an electric guitar, and wherein said pair of lead connections are respectively connected to a nut and a bridge which are in turn electrically connected to the opposite ends of each string, respectively.
		The amplifier of the present invention is a preamplifier necessary for electrical amplification of the electric phenomena which cannot be attained by the conventional amplifier with high impedance on the input side.
		Thus, according to the present invention, the amplifier 4 amplifies electrical signals (piezoelectric and/or pyroelectric signals) generated in the structure 1 subject to an external force and stress, enabling the mechanical state of the structure 1 to be observed electrically.
	www.freepatentsonline.com /5484958.html (6322 words)

	Pyroelectricity (Site not responding. Last check: 2007-10-10)
		Pyroelectricity es el potencial eléctrico creado en ciertos materiales cuando se calientan.
		Pyroelectricity se puede visualizar como un lado de un triángulo, donde cada esquina representa estados de la energía en el cristal: energía cinética, eléctrica y termal.
		Pyroelectricity no es definitivamente un nuevo concepto, pero la investigación y la aplicación de la característica útil continúa a este día.
	www.yotor.net /wiki/es/py/Pyroelectricity.htm (460 words)

	Re: Reader about pyroelectric and piezoelectric crystals
		Pyroelectricity refers to the change in polarization by changes to structure from thermal effects.
		PYROELECTRICITY: Spontaneous polarization is temperature dependent, so a good perturbation probe is a change in temperature which induces a flow of charge to and from the surfaces.
		Pyroelectric materials can be used as infrared and millimeter wavelength detectors, and I have even read some talk of using them as TV tubes (small ones).
	www.madsci.org /posts/archives/aug97/871490370.Ph.r.html (584 words)

	Pyroelectricity: Definition and Links by Encyclopedian.com (Site not responding. Last check: 2007-10-10)
		...Pyroelectricity Pyroelectricity Pyroelectricity is the electrical potential...processes behind pyroelectricity.
		Pierre Curie and his brother, Jacques, studied pyroelectricity...
		Pyroelectricity is definitely not a new concept, but research and application...
	www.encyclopedian.com /py/Pyroelectricity.html (423 words)

	L281-L283 (Site not responding. Last check: 2007-10-10)
		Pyroelectricity has been observed in polytrifluoroethylene, which was strongly enhanced in the sample subjected to rapid quenching from the melt.
		The pyroelectric coefficient showed anomalous behavior of changing signs twice over the temperature range of 100 to 330 K. On this point, the nature of the pyroelectricity in polytrifluoroethylene was greatly different from that in other pyroelectric fluorocarbon polymers.
		It was suggested from the temperature dependence of the pyroelectric coefficient that the origin of the pyroelectricity was the dipole motions in the amorphous region.
	jjap.ipap.jp /link?JJAP/22/L281 (150 words)

	The Bard Observer (Site not responding. Last check: 2007-10-10)
		In contrast, this new generator uses a crystal of lithium tantalate in conjunction with deuterium as its fuel, a type of material known as a pyroelectric, and requires a temperature change of around 50 degrees to operate.
		Indeed, the true genius of the generator lies in its use of the lithium tantalate crystal as its core, and the manipulation of its pyroelectricity.
		Pyroelectricity, or electric fields being produced by temperature changes, is by no means a new phenomenon, having been written about as far back as 314 BC by Theophrastus, an Aristotelian known as a great popularizer of science and rumored to have been so trusted by Aristotle that he made Theophrastus the guardian of his children.
	student.bard.edu /observer/articles/news/104 (736 words)

	MaNEP - Switzerland. Ferroelectricity and its Applications
		Pyroelectric materials have a spontaneous polarization whose amplitude changes under the influence of temperature gradients.
		All ferroelectrics are piezoelectric and pyroelectric, but they additionally possess a reversible, non-volatile macroscopic spontaneous electric dipole moment in the absence of an external electric field.
		In particular, their piezoelectric, dielectric and pyroelectric properties have been exploited in diverse applications, from accelerometers (airbags), ferroelectric random access memories (FeRAMs), electro-optical devices (thermal imaging), high frequency devices for medical imaging (ultrasonic-based imaging) and surface acoustic wave (SAW) devices (high frequency telecommunication filtering), to embeded Smart Systems (active vibration control) and many more.
	www.manep.ch /en/technological-challenges/ferroelectrics.html (996 words)

	Mineral Resources: Electrical Properties
		Conduction in mineral terms is the ability of a mineral to conduct electricity.
		Pyroelectricity is where a mineral develops electrical charges when exposed to temperature changes.
		Conduction is very useful in distinguishing true metals, but pyroelectricity and piezoelectricity are not practical testing methods for normal mineral collectors.
	www.minerals.net /resource/property/electric.htm (153 words)

	748-753 (Site not responding. Last check: 2007-10-10)
		Pyroelectricity in polytrifluoroethylene was studied in detail on unoriented samples.
		The pyroelectricity was found to be anomalous as regards the temperature dependence of the pyroelectric coefficient, since the latter changed signs twice over the temperature range 100 to 350 K. Also, the sample with the lowest initial crystallinity exhibited the greatest degree of pyroelectric activity.
		Crystallization coupled with poling was found to be responsible for the pyroelectricity, i.e., spontaneous polarization was induced in the new crystalline region developed during the poling process, and not in the existing crystalline region, because it is difficult for the main chain in the crystal to rotate.
	jjap.ipap.jp /link?JJAP/23/748 (281 words)

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