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Q & A: pyro and ferroelectricity

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Most recent answer: 08/12/2008
Q:
WHAT ARE THE DIFFERENCES BETWEEN FERRO ELECTRIC MATERIALS AND PYRO ELECTIRIC MATERIALS?
- sandhya (age 15)
visakhapatnam,andhra pradesh,india
A:
Pyroelectric materials are ones in which the net electric dipole moment changes as a function of temperature. If you make a capacitor out of a slab of one of these materials (oriented along a suitable direction) as the temperature is changed a voltage will develop across the capacitor, and a current will flow if the two sides are connected.

Ferroelectric materials are a subset of pyroelectric materials. In a ferroelectric, at high temperatures there's no net dipole moment, but domains with dipole moments form at a specific temperature as the material is cooled. If an electric field is applied, the direction of the dipole moment can be switched. Since the size of the dipole moment is temperature-dependent, these domains are pyroelectric. If you cool a ferroelectric material in zero field, however, its pyroelectricity might not be noticable because signals from different domains pointing different directions can cancel.

Some pyroelectric materials have a temperature-dependent moment all the way up to their melting point, and the moment is not switchable with an applied field so these wouldn't be called ferroelectric.

Mike W.

(published on 08/12/2008)

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