# Pyroelectricity

### From Online Dictionary of Crystallography

##### Revision as of 06:54, 6 March 2006 by AndreAuthier (talk | contribs)

Pyroélectricité (*Fr*). Pyroelectrizität (*Ge*). Pyroelectricidad (*Sp*).

## Definition

Pyroelectricity is the property presented by certain materials that exhibit an electric polarization *P _{i} * when a temperature variation δ

*T*is applied uniformly:

*P _{i} * =

*p*δ

_{i}*T*

where *p _{i} * is the pyroelectric coefficient.

The converse effect is the electrocalorific effect.

## Pyroelectric point groups

The geometric crystal classes for which the piezoelectric effect is possible are determined by symmetry considerations (see Curie laws). They are the classes of which the symmetry is a subgroup of the symmetry associated with that of the electric field, *A*_{∞} ∞*M*:

1, 2, 3, 4, 6, *m*, 2*mm*, 3*m*, 4*mm*, 6*mm*

## History

The appearance of electrostatic charges upon changes of temperature has been observed since ancient times, in particular on tourmaline. It is Sir David Brewster who coined the term 'pyroelectricity' (Brewster D., 1824, *Edinburgh. J. Sci.*, **1**, 208-215, *Observations on the pyroelectricity of minerals*; Brewster D., 1824, *Poggendorf Ann. Phys.*, **2**, 297-307, *Beobachtungen über die, in den Mineralien, durch Wärme erregte Electricität*.

## See also

Section 10.2 of *International Tables of Crystallography, Volume A*

Section 1.1.4 of *International Tables of Crystallography, Volume D*