{"id":2689,"date":"2015-06-30T08:00:17","date_gmt":"2015-06-30T14:00:17","guid":{"rendered":"https:\/\/www.ulprospector.com\/knowledge\/?p=2689"},"modified":"2019-08-23T03:09:20","modified_gmt":"2019-08-23T09:09:20","slug":"pe-piezoelectric-materials","status":"publish","type":"post","link":"https:\/\/ulprospector.ul.com\/2689\/pe-piezoelectric-materials\/","title":{"rendered":"Piezoelectric Materials"},"content":{"rendered":"

Piezoelectricity is the electric charge that accumulates in certain solid materials in response to applied mechanical stress. Materials exhibiting the piezoelectric effect also exhibit the reverse – the internal generation of a mechanical strain resulting from an applied electrical field. Andy Pye reviews the developments in this area, with special emphasis on polymer formulations.<\/em><\/p>\n

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Fig 1. A piezoelectric disk generates a voltage when deformed (change in shape is greatly exaggerated).<\/figcaption><\/figure>\n

Before World War II, researchers discovered that certain ceramic materials could be made piezoelectric when subjected to a high polarising voltage, a process analogous to magnetising a ferrous material. One of the first practical applications of the technology was made in the 1920’s by another Frenchman, Langevin, who developed a quartz transmitter and receiver for underwater sound – the first sonar.<\/p>\n

Piezoelectricity is exploited in applications such as the production and detection of sound, generation of high voltages, electronic frequency generation, microbalances, to drive an ultrasonic nozzle, and ultrafine focusing of optical assemblies. It is the basis of a number of scientific instrumental techniques with atomic resolution, the scanning probe microscopies such as STM, AFM, MTA and SNOM, as well as everyday uses, such as acting as the ignition source for cigarette lighters, push-start propane barbecues, and quartz watches.<\/p>\n

A piezoelectric sensor is a device that uses the piezoelectric effect, to measure changes in pressure, acceleration, temperature, strain, or force by converting them to an electrical charge. Although originally discovered in 1880 by French physicists Jacques and Pierre Curie, it was only in the 1950s that manufacturers begin to use the piezoelectric effect in industrial sensing applications. Since then, this measuring principle has been increasingly used, and has become a mature technology with excellent inherent reliability. It has been successfully used in medical, aerospace, nuclear instrumentation, as a tilt sensor in consumer electronics or a pressure sensor in the touch pads of mobile phones.<\/p>\n

In the automotive industry, piezoelectric elements are used to monitor combustion when developing internal combustion engines. The sensors are either directly mounted into additional holes into the cylinder head or the spark\/glow plug is equipped with a built-in miniature piezoelectric sensor.<\/p>\n

Sensing materials<\/strong><\/h3>\n

There are three basic classes of piezoelectric materials used in microfabrication:<\/p>\n