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Ferro-electricity is the property of some dielectric materials to keep a net residual polarization even after the electric field is removed. They tipically present a hysteresis cycle doing this.

I know that Pyro-electricity is due to an asymmetry of position of negative and positive ions in the crystal structure, such that when thermally dilatated a net polarization is created along some direction. Pervoskite is one such crystal structure that permits this:

                                            \text{Pervoskite structure under pyro-electric effect}

Note: a similar effect is found in Piezo-electrics where it's instead a mechanical stress to force a polarization in certain directions. While there could exist some piezo-electric material not pyro-electric, is not true the opposite. I believe the reason for this is that more modes of deformation are available to mechanical deformation rather than those to thermal deformation, moreover all modes of deformation are coverable by a certain mechanical deformation.

But i don't understand the necessary connection between Ferro-electricity and Pyro-electricity, where respectively electric field and thermal deformation are involved, in particular why does not exist any ferro-electric material which is not pyro-electric?

Any help is appreciated, thanks

Giorgio Pastasciutta
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1 Answers1

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I think crystal structure (https://en.wikipedia.org/wiki/Pyroelectricity) explains this. Say if the pervoskite (which is pyro with natural polarisation P) red atom jumps from upper half to lower half of gold enclosure and polarisation reverses to downward direction when applying an electrical field, then it is ferroelectric too, otherwise only pyroelectric. So perhaps it is an electric potential energy barrier issue that determines ferroelectricity of a polar crystal which is always pyro.

Note, this assumes stable reversal. High intensity and / or short-lived reversals can happen and if observed can settle your disquiet.

MKhomo
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