Paraelectricity
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Paraelectricity is the ability of many materials (specifically ceramic crystals) to become polarized under an applied electric field. Unlike Ferroelectricity; this can happen even if there is no permanent electric dipole that exists in the material, and removal of the fields results in the polarization in the material returning to zero[1]. The mechanisms which give rise to paraelectric behaviour are the distortion of individual ions (displacement of the electron cloud from the nucleus) and the polarization of molecules or combinations of ions or defects.
Paraelectricity occurs in crystal phases in which electric dipoles are unaligned (i.e. unordered domains that are electrically charged) and thus have the potential to align in an external electric field and strengthen it. In comparison to the ferroelectric phase, the domains are unordered and the internal field is weak.
The LiNbO3 crystal is ferroelectric below 1430 K, and above this temperature it turns to paraelectric phase. Other perovskites similarly exhibit paraelectricity at high temperatures.
Paraelectricity may provide an alternative to the traditional heat pump. A current applied to a paraelectric material will cause it to cool down - which could be useful for refrigeration or for cooling computer chips.
[edit] See also
- ^ Chiang, Y. et al: Physical Ceramics, John Wiley & Sons 1997, New York
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