Piezoelectric Effect

The piezoelectric effect is the generation of the electric charge by a crystalline substance upon subjecting it to pressure or stress. The effect exists in  the natural crystals, such as quartz (chemical formula Si02) and poled (artificially polarized) human-made ceramics and some polymers, such as PVDF. It is said that piezoelectric material possesses ferroelectric properties. The name was given by an analogy with ferromagnetic properties, though there is no iron in most piezoelectrics. The word piezo comes from the Greek “pigeon” meaning "to press." The Curie brothers discovered the piezoelectric effect in quartz in 1880, but very little practical use was made until 1917 when another Frenchman, professor P. Langevin used x-cut plates of quartz to generate and detect sound waves in water. His work led to the development of sonar. In 1927 A.Mcissncr, A pro­posed a basic, yet quite descriptive model of the piezoelectric effect.

Since time immemorial, people in India and Ceylon - where tourmaline crystals are easily found - had observed that such crystals, when thrown into hot ashes, would strongly attract surrounding ash particles after a few moments, only to repel them again a little later. Dutch merchants brought this knowledge, together with the first tourmaline crystals, to Europe around 1703, where tourmaline was then often called "Ceylon magnet" [Dietrich 1985]. Linnaeus gave it the scientific name "lapis electricus" in 1747 already, although the electrical nature of this phenomenon was proven only in 1756 by Aepinus who observed the opposite polarities at the both the ends of the heated tourmaline crystal. Sir David Brewster named this effect "pyrolectricity" (from the Greek "pyro", meaning fire) in 1824.

Already Hauy and Becquerel tried to find a relationship also between mechanical stress and electric polarization but the findings they reported were far from conclusive. The experimental setups at the time were always prone to be perturbed by the omnipresent triboelectricity (electric charge produced through friction) in the insulators used, such as amber.

The direct piezoelectric effect (from the Greek "piezin", meaning to press) was discovered by the brothers Jacques and Pierre Curie and first announced during the session of the Academie des Sciences in Paris on 2 August 1880 (Curie 1880]. They reported about an existing relationship between mechanical load and electric polarization but did not use the term piezoelectricity yet.

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