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Do dimensions of a piezoelectric material affect voltage?

  1. Aug 17, 2015 #1
    Consider a block of a piezoelectric material sandwiched between two parallel plate conductors, sort of like a parallel plate capacitor with a piezoelectric material as its "dielectric."

    If applying the same pressure to two of these configurations, does the thickness of the piezoelectric block affect the generated voltage?
     
  2. jcsd
  3. Aug 17, 2015 #2

    DEvens

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    What would happen if you stacked two such devices on top of each other, and then squeezed both of them with the same force? What happens to two springs when arranged end-to-end?

    I think the major thing you will find is that a thicker crystal will have different changes in geometry when you apply a given amount of force. So if the system you are trying to measure behaves differently under such different small changes in geometry, you may get different results.

    Example: Suppose you are trying to measure the change in shape of a surface by putting p-crystals at intervals. If the surface is changing due to forces that are very large compared to the force required to change the size of the crystal, then the crystal being there may not change the shape of the surface very much. You might see this in the case of machining a surface then putting it on a gauge to check the change in thickness. So the force required to squish the crystal might be tiny compared to the force required to deflect the surface.

    I don't actually know whether any process actually uses p-crystals in such a fashion.

    But if you were looking for changes due forces that are small compared to the force to compress the crystal, then it might make a difference. Two crystals stacked will deform more (in total) under a given force, just as two springs end-to-end will deform more (in total) under a given force. So if you were looking for the change in geometry of a tank being pressurized, and the crystal required a force similar to the pressure you were using in the tank, then two crystals stacked might well produce a very different signal to one crystal.
     
  4. Aug 20, 2015 #3
    If by thickness you mean the distance between the plates then yes.
    The voltage is proportional to this distance.
     
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