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Thread: Piezoelectric effect

  1. #1 Piezoelectric effect 
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    How does qm describe it?

    Is it via a continuous energy band or discrete cells changing state?

    Wikipedia has not been helpful.
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  2. #2  
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    Quote Originally Posted by Useful Idiot View Post
    How does qm describe it?

    Is it via a continuous energy band or discrete cells changing state?

    Wikipedia has not been helpful.
    I haven't seen a specific QM description (largely because I haven't looked), but it would likely go something like this: The supported mechanical modes are quantised, so you'd be looking at the distribution of phonon energy and momenta. However, in a macroscopic piezolectric material, you'd get a quasi-continuum that would produce convergence with the standard, classical description of piezoelectricity.

    Coupling to that mechanical domain, of course, is the electrical part. A mechanical strain displaces charge centers, the displaced charge exerts mechanical stress, and on it goes.

    That broad description omits many details, of course. What specific part are you interested in?
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  3. #3  
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    That's very good, thank.

    I'd forgotten that the potential wells will have quantized energy levels. That's how rusty on quantum mechanics I've become.

    I'm interested in similarities and differences with ferromagnetic material. Ferromagnetic material form domains , were I presume each crystalline cell has the same spin state. As quartz piezoelectric materials can be formed from a single crystal (I think) it seems there would be not be partitioning into domains. However there seem to be polycrystalline ceramics that might support piezoelectric domains. I have no idea.
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  4. #4  
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    Quote Originally Posted by Useful Idiot View Post
    That's very good, thank.

    I'd forgotten that the potential wells will have quantized energy levels. That's how rusty on quantum mechanics I've become.

    I'm interested in similarities and differences with ferromagnetic material. Ferromagnetic material form domains , were I presume each crystalline cell has the same spin state. As quartz piezoelectric materials can be formed from a single crystal (I think) it seems there would be not be partitioning into domains. However there seem to be polycrystalline ceramics that might support piezoelectric domains. I have no idea.
    I'm fairly certain that your conjecture is correct. Lead zirconate titanate is a common piezoelectric ceramic, and the way it is typically produced does not involve any seeded or epitaxial growth, so the result is almost certainly polycrystalline. The implication is that the individual grains would act as separate piezoelectric domains. Quartz, as it is used in modern electronics, is generally monocrystalline (or very nearly so), and would therefore not have (m)any subdomains.
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