
	Where results make sense

Topic: Pyroelectric effect

Related Topics

Piezoelectric effect

Triboelectric effect

Electrical phenomenon

Piezoelectricity

Electroluminescence

Ferroelectric effect

Static electricity

Photoconductivity

Forbidden Planet

Frequency standard

SECAM

United States Constitution

Geography

List of places with fewer than ten people

Kou Shibasaki

In the News (Tue 1 Dec 09)

Northern Trust

Marvin Harrison

Peter Chernin

Gary Locke

Match Play

Penelope Cruz

Mickey Rourke

AR Rahman

Danny Boyle

Hugh Jackman

	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)

	Xerographic charging and transfer using the pyroelectric effect - Patent 5678145
		Heating and cooling a pyroelectric film, such as, polyvinylidene fluoride induces thermal expansion or contraction which create surface charge density changes that can be used to charge a photoconductive surface and/or transfer an image from a photoconductive surface to a copy sheet.
		The pyroelectric device of claim 2, wherein said blade is adapted to clean and neutralize said layer of pyroelectric film.
		However, it should be understood that the pyroelectric charging and transfer devices of the present invention could be used with any machine that requires charging a dielectric material and transferring an image from that dielectric material to a piece of support material.
	freepatentsonline.com /5678145.html (3664 words)

	Pyroelectricity: From Ancient Curiosity to Modern Imaging Tool - Physics Today August 2005
		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.
		Jacques and Pierre Curie proposed that the electrical effects due to nonuniform heating of quartz crystals might have been caused by pressure, a speculation that led to their 1880 discovery of piezoelectricity (related to pyroelectricity as discussed in box 1).
		(The pyroelectric effect, based on different physics, does not depend on the size of the bandgap.) These materials are difficult to grow and fabricate into devices, and they require cooling, usually to 77K, for operation in the long-wavelength IR spectrum.
	www.physicstoday.org /web_bin/pt/vol-58/iss-8/p31.html (2436 words)

	Ph.D. Degree (Site not responding. Last check: 2007-10-12)
		The pyroelectric effect is observed only in materials whose polar entities are arranged in a non-centrosymmetric organisation.
		Organic thin films are interesting candidates for pyroelectric detectors due to their ease of processing compared with ceramics and single crystals and due to the way in which their functionality, at the molecular and macroscopic level, can be controlled.
		This study has revealed for the first time that there exists an optimum thickness effect in the pyroelectric activity of alternate layer LB films and that the measured coefficient is sensitive to the overlap area of the metal electrodes which form part of the pyroelectric devices.
	w3.balikesir.edu.tr /~rcapan/PhD.htm (275 words)

	Dr. Yaron Danon
		This research is focused on understanding the pyroelectric effect in order to use it to effectively accelerate electrons and ions.
		The distinguishing trait of pyroelectric crystals is that the polarization of the crystal is altered dramatically with changes in the temperature of the crystal, such that the polarization is no longer masked and a large voltage can be observed across the crystal.
		The geometry use to demonstrate thorium fluorescent is shown in Figure 5; such geometry utilized the pyroelectrically generated x-rays to fluoresce the thorium sample in transmission geometry and the spectrum obtained is shown in figure 6.
	www.rpi.edu /~danony/Research/Pyro.htm (1016 words)

	Patent-Invent: Thermoelectricity (Peltier-Seebeck Effect)
		The Peltier-Seebeck effect, or thermoelectric effect, is the direct conversion of heat differentials to electric voltage and vice versa.
		The Peltier, Seebeck, and Thomson effects are reversible; Joule heating is not, and cannot be, under the laws of thermodynamics.
		Such effects can be observed in conductors where the carriers are ions, or in semiconductors where the carriers are holes or electrons.
	www.patent-invent.com /electricity/inventions/thermoelectricity.html (1149 words)

	High-sensitive bolometers (Site not responding. Last check: 2007-10-12)
		The sensors operate using the pyroelectric effect and the effect of resistance variation of a thin golden foil irradiated by visible and soft X-ray radiation.
		Pyroelectric sensors generate current during the interval of temperature variation inside the plate.
		To reduce the effect of sensor heating by neutrons an additional channel is used which is covered with aluminum foil.
	www.ioffe.rssi.ru /RT/IWRFRI2000/a9.html (287 words)

	kF6
		Since the pyroelectric signal is dominated by regions where the thermal wave amplitude is high, ist depth-profile can be measured by scanning the frequency over several orders of magnitude.
		The depth-profile of the pyroelectric coefficient p(x) (x: coordinate in space) is buried in a integral equation for I
		Measurement of the pyroelectric signal of several samples.Calculation of the depth-profile of the pyroelectric coefficient.
	www.uni-potsdam.de /u/physik/fprakti/kF6a.htm (436 words)

	NEER Program (Site not responding. Last check: 2007-10-12)
		Pyroelectric x-ray generation is a novel technique for creating small x-ray devices that can be used in materials analysis, medical imaging, and other areas of scientific research.
		Pyroelectric x-ray generation occurs when a pyroelectric crystal is heated or cooled in a vacuum, causing a very large potential to form across the crystal.
		Preliminary research we performed has shown that the energy of the x-rays in a pyroelectric x-ray generator can be doubled by using two crystals in series instead of a single crystal.
	neer.inel.gov /abstract.asp?ProjectID=126 (272 words)

	Pyroelectric behaviour of cement-based materials
		The pyroelectric effect, which is useful for temperature sensing, was observed in cement-based materials.
		Carbon fibre cement paste and plain cement paste are comparable in the pyroelectric voltage, though the pyroelectric coefficient is higher for carbon fibre cement paste than plain cement paste.
		The pyroelectric effect in cement-based materials is attributed to the increase in mobility of the ions as the temperature increases.
	www.azobuild.com /details.asp?ArticleID=7415 (135 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)

	Applications of Ferroelectric Ceramic Materials
		This is called the pyroelectric effect which was first discovered in tourmaline by Teophrast in 314 B.C. and so named by Brewster in 1824 [15].
		The piezoelectric and pyroelectric properties of these polymers are due to the remnant polarization obtained by orienting the crystalline phase of the polymer in a strong poling field.
		Hence the piezoelectric and pyroelectric properties depend on the degree of crystallinity of the polymer and the ferroelectric polarization of the crystalline phase [63, 64].
	www.rci.rutgers.edu /~ecerg/projects/ferroelectric.html (10045 words)

	Pyroelectric
		Pyroelectric Infrared Detectors (PIR) convert the changes in incoming infrared light to electric signals.
		Pyroelectric materials are characterized by having spontaneous electric polarization, which is altered by temperature changes as infrared light illuminates the elements.
		Since our sensor series uses this effect they can be used at ambient temperature even in the presence of thermal noise.
	www.fuji-piezo.com /prodpyro.htm (103 words)

	Tuller Group Homepage
		The microscopic origin of the piezoelectric effect is the displacement of ionic charges within a crystal structure.
		Ferroelectric materials are a sub-class of pyroelectric materials in which the direction of the electric dipole can be reversed by applying an electric field.
		The electro-optic effect is the change in the refractive index as a function of an externally applied electric field.
	electroceramics.mit.edu /about.htm (726 words)

	SPIE Proceedings Vol. 3182
		The results were explained by the effect of gettering of unintentional donor impurities in the melt by Dy, as well as by the effect of strain modification in the layers due to the possible incorporation of Dy.
		The approximating analytical expressions obtained are applied in calculations of the effect of TSR on the characteristics of photodiodes, solar cells, light-emitting diodes and diode lasers.
		Abstract: Peculiarities of photovoltaic effect (PVE) in graded-band- gap (GBG) layers with intrinsic type of conductivity and linear coordinate dependence of energy gap in the conditions of layer illumination by strongly absorbed monochromatic light are investigated theoretically.
	www.spie.org /web/abstracts/3100/3182.html (9463 words)

	ELAN - Lithium Tantalate Substrates for Pyroelectric Detectors
		Pyroelectric effect is change of polarization with temperature resulting in a polarization current within a crystal.
		In practice, the effect can be measured if electrodes are applied to crystal surfaces normal to polar axis and connected through an external circuit.
		So pyroelectric substrate (thin plate of pyroelectric material with proper electrodes) is a heart of pyroelectric detectors featuring very broad operation wavelength with extremely fast response time.
	www.elan.spb.ru /eng/27.html (344 words)

	Sensors & Functional Materials: Characterisation of Ferroelectric Thin Films
		Simply put a laser diode is used to generate a thermal pulse in the sample, and this induces a pyroelectric current which is measured, via a current to voltage convertor, using lock in amplification techniques.
		In order that the induced pyroelectric current can be measured it is necessary to convert the current signal to a voltage, using a virtual earth current to voltage converter.
		Since the signal levels generated by the pyroelectric effect are generally quite small it is necessary to use lock in amplification techniques to distinguish the real signal above the noise.
	www.npl.co.uk /materials/functional/thin_film/characterisation/limm_method.html (844 words)

	Adaptive Equalization for Acoustic Stereo Effect (Site not responding. Last check: 2007-10-12)
		The pyroelectric effect is a phenomenon that is attributed to certain materials that are able to develop a charge as a result of a change in temperature.
		A substance’s pyroelectric coefficient is defined as the substance’s change in polarization with respect to temperature.
		By measuring the change in temperature as well as the current response of the pyroelectric material, the pyroelectric coefficient can be determined and used to help predict the behavior of the material for various applications.
	www.ee.psu.edu /reu/PastActivities/2003REUStudentsandFacSummary/VonEden_Guo_Proj.htm (188 words)

	PCB Piezotronics, Inc. - Tech Support
		Piezoelectric accelerometers rely on the piezoelectric effect of quartz or ceramic crystals to generate an electrical output that is proportional to applied acceleration.
		These effects can contribute to erroneous output signals when used on thin, sheet-metal structures or at low frequencies in thermally unstable environments, such as outdoors or near fans and blowers.
		One of the most important considerations in dealing with accelerometer mounting is the effect the mounting technique has on the accuracy of the usable frequency response.
	www.pcb.com /techsupport/tech_accel.php (3787 words)

	-MRS-
		Pyroelectric properties of GaN were studied in two different regimes: (i) uniform sample heating regime; (ii) under applied temperature gradient along the sample.
		Effect of substrate nitridation, growth temperature and plasma modification on the quality of the layer are discussed.
		The effect of different growth temperatures and substrates, mismatch of thermal expansion coefficients, and crystallographic orientation is considered in the analysis.
	lucy.mrs.org /meetings/fall98/absbook/AbstractBookG.html (18439 words)

	ME 117/220 Lecture #11
		As for piezoelectricity, pyroelectricity is a phenomena in which a change in temperature causes thermal expansion, which causes the appearance of charge (through the piezoelectric effect) (see Fig.
		This very expensive material offers the best pyroelectric coefficients, and is commonly used for IR detection in laboratory spectrometers, and in early motion detection systems.
		A variety of other pyroelectric materials are also available - it is generally true that any material which is piezoelectric is also pyroelectric.
	www.yale.edu /eas996/smart/lect_11.html (1462 words)

	APPLIED PHYSICS: A SIMPLE NEUTRON GENERATOR
		5) The pyroelectric effect -- the fact that some materials become charged when heated -- was probably first recorded in 314 BC by Theophrastus[2], Aristotle's student and successor, from his studies of the gemstone tourmaline.
		This effect was used by Brownridge[3,4] to produce a small pyroelectric X-ray generator, of which a commercial version, powered by a 9-volt battery, is now available[5].
		The effect is widely used as the basis of field-ion microscopy.
	scienceweek.com /2005/sw050520-2.htm (1347 words)

	4. Neumann's Principle
		The application of the matrices corresponding to these basic operations (the generating matrices) are sufficient to obtain the effect due to the symmetry of a crystal class on the given tensor in question.
		Finally it should be observed that in some cases simple geometric considerations enable the determination of the independent components of the tensors representing the physical properties.
		It is easy to see that no pyroelectric effect can exist in a crystal possessing a centre of symmetry.
	www.iucr.org /iucr-top/comm/cteach/pamphlets/18/node4.html (1299 words)

	Infrared and Electro Optical
		Servo began building pyroelectric detectors using proprietary processing techniques, as commercial products several years ago, but early on noted that they would be very effective if used as an Earth sensor.
		Because of the nature of the pyroelectric effect, a radiant contrast must be created between the detector and some known temperature source.
		The copolymer has a high pyroelectric output and is ideal for manufacture as it can be uniformly spun onto a thermal isolation structure to thickness' of.3 microns or lower, chemically delineated before curing, and delineated using Reactive Ion Etch (RIE) afterward.
	www.servo.com /elecpd1.htm (682 words)

	Chapter 4: Piezoelectricity (Site not responding. Last check: 2007-10-12)
		The piezoelectric effect is the production of electrical polarization in a material by the application of mechanical stress.
		The converse piezoelectric effect is a possible molecular mechanism by which an organism could detect an external field.
		Pyroelectricity is the development of electric charges on the surface of a material when it is heated; all pyroelectric materials are piezoelectric (but the converse is not true).
	www.ortho.lsuhsc.edu /Faculty/Marino/EL/EL4/Piezo.html (734 words)

	Piezo Systems - Frequently Asked Questions
		This may seem counter-intuitive at first; however, you must remember that the basis for the piezoelectric effect is inter-atomic electric fields, and electric fields are not affected by temperature at all.
		However, if the cycle time or either endpoint is changed, hysteresis and creep effects cause non-repeatable motions.
		This is due to the pyroelectric properties of piezoceramic.
	www.piezo.com /tech3faq.html (2674 words)

	Millimeter wave imager device using pyroelectric effect - Patent 5530247
		Infrared imaging systems which incorporate sensors that make use of the pyroelectric effect of ferroelectric films are known in the art.
		The pyroelectric effect occurs as a result of radiant energy causing an increase in the temperature of a ferroelectric material, which in turn causes a charge build-up in the material that can be detected.
		In accordance with the teachings of the present invention, a passive millimeter-wave imaging system is disclosed which incorporates an array of ferroelectric elements that utilize the pyroelectric effect for detecting radiation in the millimeter-wave range.
	www.freepatentsonline.com /5530247.html (2669 words)

Try your search on: Qwika (all wikis)