Seignette electricity

Seignette, Pierre (1660-1719) was a French pharmacist who first prepared Rochelle salt in c. 1675. In the early literature the phenomenon of ferroelectricity was more often referred to as Seignette-electricity or Rochelle-electricity. ... 

Seignette-electric. Seignette salt is the alternative name for Rochelle salt (Na-K tartrate). Crystals of this composition are markedly piezo-electric and were used, for this property, before titanate... 

The physical phenomenon of ferroelectricity-initially termed Seignette electric-ity-was first discovered in sodium potassium tartrate tetrahydrate (Rochelle or Seignette salt), and later in analogy to ferromagnetic behavior coined ferroelectricity by Valasek (1924). Its history is listed in Table 8.4, which shows the impressive change from a curious isolated property to a widespread and economically enormously important and promising ceramic engineering material (Cross and Newnham, 1987). 

Above a specific temperature, the Curie temperature, a ferroelectric substance becomes paraelectric since the thermal vibrations counteract the orientation of the dipoles. The coordinated orientation of the dipoles taking place during the ferroelectric polarization is a cooperative phenomenon. This behavior is similar to that of ferromagnetic substances, which is the reason for its name the effect has to do nothing with iron (it is also called seignette or rochelle electricity). 

Pyroelectricity is a property inherent in crystals with unique polar axes that are, consequently, without a center of symmetry. However, as opposed to piezoelectricity not all symmetry groups (point groups) lacking a center of symmetry are pyroelectric, whereas all pyroelectrics are also piezoelectrics. Most pyroelectrics belong to the hnear dielectrics as the polarization is linearly dependent on the electric field. However, some-for example, KDP and Seignette salt-are nonhnear pyroelectrics-that is, they are ferroelectrics. 

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