The application of a constant electric field to piezoelectric crystals results in a change of approximately 0.1% in their static dimensions. This phenomenon is explained through the behavior of the crystal structure, particularly in a zinc sulfide (ZnS) face-centered cubic (fcc) unit cell, where the positioning of sulfur ions alters the equilibrium of zinc ions, creating an electric dipole. The discussion raises critical questions about the limits of static dimensions under continuous stress and the nature of electric potential across the crystal.
PREREQUISITESMaterials scientists, electrical engineers, and students studying piezoelectric phenomena will benefit from this discussion, particularly those interested in the mechanical and electrical properties of crystals.
Thank you!Stephen Hodgson said: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!