Applications pyroelectric sensors

A large number of apphcations have been proposed for piezoelectric polymers. The types of applications can be grouped into live major categories sonar hydrophones, ultrasonic transducers, audio-frequency transducers, pyroelectric sensors, and electromechanical devices. The principal polymers of interest in these applications are PVDF and copolymers of vinylidene fluoride and trifluoroethylene. 

PbTi03, for pyroelectric detectors and hydrophones LiTa03, for pyroelectric sensors Pb(Sci/2Tai/2)03, (Bao.6oSro.4o)Ti03, for pyroelectrics Pb(Zri Ti )03, for piezoelectric applications of all types... 

As mentioned above, LC elastomers, especially LSCE with monodomain order, anisotropic LC networks, and gels, may be optimized to make a kind of smart material for molecular switching and piezoelectric or pyroelectric sensors, because of their sensitivity to environmental conditions (electric or stress fields, temperature, and radiation, etc.) and memory effect. Other applications include wave-guide, polarizers, optical filters, alignment, and compensation films for LCD displays. 

This expression is the basic description for the use of the pyroelectric effect in a host of sensor applications including the well known optical detection devices (82,83). A particularly useful way of describing this type of system is with an equivalent circuit where the pyroelectric current generator drives the pyroelectric impedance and the measuring amplifier circuit as shown in Figure 11. 

The OMA technology has been recently applied to infra-red spectroscopy ( 18) as well. A pyroelectric vidicon (utilizing a triglycine sulfate as the sensor element) has been used as a thermal rather than a photon multichannel detector. Simultaneous spectral detection, in the 1-30 um spectral region, was accomplished that has proven to be particularly useful for IR pulse laser applications, Fig.12,... 

Electret materials are meanwhile used in a large number of modern high-tech applications including microphones, acoustic sensors, transducers, radiation and pollution dosimeters, power generators, filters, and many more. Additionally, electret technology is of great interest in the field of biomaterials, for instance in callus formation and wound healing [10, 11], When used in cellular or in multilayer sandwich structures, polymer electrets can exhibit piezoelectricity. Such materials are ferroelectrets, as they show typical features of ferroelectric materials such as piezo-and pyroelectricity [12-17],... 

The relaxational behaviour of polyvinylidene fluoride (PVDF) is of interest. Its p phase exhibits piezo- and pyroelectric properties and so it is used in various devices, such as sensors, transducers or actuators for different applications. Typically such materials are prepared through a technological process involving stretching and... 

Eickhoff, M., Schalwig, J., Steinhoff, G., Weidemann, O., Gorgens, L., Neuberger, R., Hermann, M., Baur, B., Muller, G. and Ambacher, O. (2003) Electronics and sensors based on pyroelectric AlGaN/GaN heterostructures-part B Sensor applications , physica Status Solidi (c), 6,1908-1918. 

The principle of the Thomson polymer IR sensor is represented by Fig. 14 and Fig. 15. The P(VF2 TrFE) copolymer constitues the pyroelectric layer (5-10 pm), the insulation layer is a polyimide (10 pm). The upper electrode is also the infrared absorber and is made in aluminium or gold black. The lower level is the CCD level which constitues the second electrode. The polarisation of the polymer is realized by application of 100 V/pm between the two electrodes of the pyroelectric capacitor. 

This pyroelectric effect can be utilized for sensors such as e.g. infrared cameras. However, in sensors that use the electromechanical effect p3To-electricity can be disturbing. The disturbing effects arise especially in low-frequency or quasi-static applications as the temperature drift is often a slow process. A one ohm resistance is applied in parallel to suppress this effect. That way, the pyroelectric induced charges are deflected and the cut-off frequency of the sensor is raised. 

Horiuchi T, Hidaka H, Fukui T, Kubo Y, Horio M, Suzuki K, Mori T (1998) Effect of added basic metal oxides on CO adsorption on alumina at elevated temperatures. Appl Catal A Gen 167 195-202 Houser EJ, Mlsna TE, Nguyen VK, Chung R, Mowery EL, McGill RA (2001) Rational materials design of sorbent coatings for explosives applications with chemical sensors. Talanta 54 469 85 Hsieh HY, Spetz A, Zemel JN (1991) Wide range pyroelectric anemometers for gas flow measurements. In Digest of technical papers of TRANSDUCERS 91. International conference on solid-state sensors and actuators, 24-27 June 1991, San Francisco, CA, pp 38-40... 

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