How Does Constant Electric Field Affect Piezoelectric Crystal Dimensions?

[kiutukri]

Homework Statement

Piezoelectric crystals will change about 0.1% of their static dimension when an external electric field is applied to the material.

Homework Equations

1. What happens with the static dimension if the external electric field applied is a constant?
2. Will the static dimension reach a limit?
3. It's always expanding and contracting?

The Attempt at a Solution

No clue

 

[Matternot]

I don't know how much you know about the crystal structure of piezoelectric crystals, but if you do, think about what happens to the unit cell:

If we consider a ZnS blende fcc Crystal unit cell with the Zn ion in the centre, as the crystal undergoes a stress, 2 of the Sulpher ions (making up the tetrahedron closer to the Zn ion and 2 get further away resulting in a shift in the equilibrium position of the Zn ion. This results in an Electric dipole.

The reverse piezoelectric effect is the movement of the Sulpher ions due to the electric field. i.e. the inverse of the paragraph above.

As for questions 2 and 3, think:
Does an finite stress result in an infinite electric field if held for a long time?
Does a constant stress result in a constant, or changing potential across the crystal?

This is the Cambridge materials page on piezoelectrics. DoITPoMS is great for all materials science in general.
http://www.doitpoms.ac.uk/tlplib/piezoelectrics/dipole.php

Hope this helps!

 

[kiutukri]

I don't know how much you know about the crystal structure of piezoelectric crystals, but if you do, think about what happens to the unit cell:

If we consider a ZnS blende fcc Crystal unit cell with the Zn ion in the centre, as the crystal undergoes a stress, 2 of the Sulpher ions (making up the tetrahedron closer to the Zn ion and 2 get further away resulting in a shift in the equilibrium position of the Zn ion. This results in an Electric dipole.

The reverse piezoelectric effect is the movement of the Sulpher ions due to the electric field. i.e. the inverse of the paragraph above.

As for questions 2 and 3, think:
Does an finite stress result in an infinite electric field if held for a long time?
Does a constant stress result in a constant, or changing potential across the crystal?

This is the Cambridge materials page on piezoelectrics. DoITPoMS is great for all materials science in general.
http://www.doitpoms.ac.uk/tlplib/piezoelectrics/dipole.php

Hope this helps!

Thank you!