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| A
piezoelectric material is one that develops an electrical potential diffence
between its faces when subjected to an applied strain. The converse process
also occurs and a piezoelectric material will change its dimensions when
a voltage is applied to it. This behavior requires crystals which lack
a center of symmetry. Displacing the free surfaces of the sample moves
its constituent ions and creates an electric dipole moment in the material.
The application of a voltage to the unstrained materail causes the relative
displacement of the positive and negative sub-lattices of the structure
and causes a strain in the material.
Crystalline quartz is a usefull piezoelectric material and is used as a source of elastic waves for testing materials. The material can also be excited at its resonant frequency and used as a stable oscillator. Other ceramic materials such as barium titanate and lead titanate are good piezoelectrics. The barium titanate unit cell with the atoms in the polarized position is shown below. |
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| From:McMahon
and Graham,
"Introduction to Engineering Materials," Merion (1992) |
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