What is Piezoelectric effect?

Piezoelectric


Piezoelectric crystals are one of many small scale energy sources. Whenever piezoelectric crystals are mechanically deformed or subject to vibration they generate a small voltage, commonly know as piezoelectricity.

  • Piezoelectric crystal, such as quartz, that produces a potential difference across its opposite faces when under mechanical stress.


Piezoelectric Materials

There are many materials, both natural and man-made.

(1) naturally piezoelectric – Berlinite (structurally identical to quartz), quartz, cane sugar, Rochelle salt, tourmaline, topaz .

(2) man-made piezoelectric –  barium titanate and lead zirconate titanate.


What Is the Piezoelectric Effect?

  • The piezoelectric effect refers to a change in electric polarization that is produced in certain materials when they are subjected to mechanical stresses. This stress-dependent change in polarization manifests as a measurable potential difference across the material.
  • An important feature to note about this phenomenon is that the process is reversible. The inverse piezoelectric effect refers to a deformation of these materials that results from the application of an electric field.
  • The deformation could lead to either tensile or compressive strains and stresses in the material depending upon the direction of the electric field, the preferred direction of polarization in the material, and how the material is connected to other adjacent structures.

How piezoelectricity works

  • Piezoelectric crystal consists of multiple interlocking domains which have positive and negative charges. These domains are symmetrical within the crystal, causing the crystal as a whole to be electrically neutral.
  • The piezoelectric effect occurs when the charge balance within the crystal lattice of a material is disturbed. When there is no applied stress on the material, the positive and negative charges are evenly distributed and so there is no potential difference. When the lattice is slightly altered (when stress is applied on the crystal), the charge imbalance creates a potential difference, often as high as several thousand volts. Even a tiny bit of piezoelectric crystal can generate voltages in the thousands.

  • However, the current is extremely small and only causes a small electric shock. The converse of this effect occurs when the electrostatic field created by electric current causes the atoms in the material to move slightly.

 

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