Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Highly Efficient Piezoelectric Ceramics

  1. Jul 22, 2007 #1
    does anyone work with piezoelectric ceramics or polymers

    i need to know so real world numbers that i just cant seem to find i think this is due to the fact that i have no real clue as to what i am doing but i would like to
    1 a base line number for efficiency as in one kilogram of pressure = how many watts volts
    2 base line cost to produce; i read that there are cheap but i need some type of base line and i just can find this
    3 base line compression of material to produce current
    4 how to manage current
    5 can piezoelectric materials be sandwiched between a layer of malleable but non conductive materials on top and non malleable but conductive materials on bottom to sort of manage the flow of electricity
     
  2. jcsd
  3. Jul 22, 2007 #2

    marcusl

    User Avatar
    Science Advisor
    Gold Member

  4. Jul 22, 2007 #3

    xez

    User Avatar

    Quickly here are a few partial responses. I could probably
    find a lot more quantitative information later.

    "1 a base line number for efficiency as in one kilogram of pressure = how many watts volts"
    Well the wattage will be quite small; piezoelectrics
    generate high voltages but very low currents. They are
    electrically polarized dielectric insulators essentially, so
    they work by mechanically separating charges but they
    are usually not capable of generating a significantly large
    current into any impedance. Usually you use either a
    high input impedance voltage measurement circuit with
    them, or for very wide bandwidths you might use some
    electrical transmission line and load that's matched to
    some value related to the impedance of your electronics
    loads and maybe also relative to the impedance of the
    piezo transducer if the design calls for that.

    The actual sensitivity in joules or volts per force
    applied etc. depends on the piezo material chosen,
    the range of forces applied, the frequency spectrum of
    the forces, the active area of the transducer etc.

    "2 base line cost to produce; i read that there are cheap but i need some type of base line and i just can find this "

    Well cheap is relative... if you're making something totally
    custom and very mechanically/electrically intricate like a
    256 sensor integrated array for ultrasound imaging,
    that'll cost a bit, especially in low quantity. If you want
    something like a piezo disc buzzer for a kid's toy in
    quantity 100,000, yeah that'd be quite cheap. Talk with
    some prospective manufacturers about your
    application's design needs and production volumes / schedules to get a better idea.

    3 base line compression of material to produce current

    Well you don't "compress" the material to as an end user
    to get it to produce an output. It just sits there in your
    device at whatever ambient pressure/temperature is
    normal for your application, and then added stresses
    on top of the static levels will produce changes in the
    electrical output. Since they're essentially electrostatic
    devices in most applications, they don't really produce
    a DC output, but they give you response indicating the
    change in forces applied over some given timescale
    from a small few seconds maximum down to nanoseconds
    for some applications and designs.
    Certainly being ceramic and fragile (somewhat) devices
    there are limits of pressure/temperature/shock/electrical
    energy input that they can be subjected to, so if you have
    specific needs in these areas that are 'extreme' then
    certainly consult an applications engineer so that you'll
    get the best design performance for delta-pressure
    sensitivity given your baseline environment.

    "4 how to manage current" -- generally either
    terminate it in some characteristic impedance of the
    sensor, or just sense it as you would an electrometer --
    high impedance buffer amplifier going to whatever your
    other circuitry is.
    If you're actively zapping the piezo electrically
    to generate a mechanical impulse like a SONAR application
    there are certainly applied energy / frequency /
    impedance matching / resonance criteria you'll need to
    sort out but those are highly application dependent.
    Same deal for crystal oscillator applications or
    acousto-optic modulators or whatever else...

    "5 can piezoelectric materials be sandwiched between a layer of malleable but non conductive materials on top and non malleable but conductive materials on bottom to sort of manage the flow of electricity" --
    Top? Bottom? Well depending on your transducer
    design you can take the electrical outputs from various
    physical places on the piezo... Generally it's between the
    areas that receive the most strain from your mechanical
    input... The contacts are generally made with contacts
    that are either metal films that are evaporated / sputtered
    on the ceramic, or they're painted-on conductive layers
    of metallic type of inks, or they're some kind of specially
    pressure-seated mechanical contacts, or with some
    particular kinds of conductive cement or whatever..
    Generally you specify the design of the transducer and
    the contact locations and also do that in the context of
    specifying or understanding the design for the
    holding cell for the transducer so it's free to communicate
    the mechanical stresses to the environment in an
    appropriately efficient way as well as to protect the
    electrical contacts and other areas of the cell / transducer
    that shouldn't be exposed to the environment.
    Generally unless you're talking about conductive rubber
    or plastic most pliable materials are non-conductors.
    If the transducer has built in "leads" or contact points
    you're free to (and encouraged to) put non-conductive
    materials all around the area of the surfaces of the
    transducer to the extent that you want to environmentally
    seal the element and its contacts from the environment.
    Obviously you'll need the contact points themselves to
    be bonded to your leads or circuit board or whatever
    electrically, but anywhere except at that point you can
    design your holder cell however you need to so that
    the mechanical support / damping / resonance / coupling /
    impedance transformation / whatever you need is
    accomplished... Of course since it is a piezo material
    stresses can cause voltages at other points on the surface
    of the material and applied voltages at other points will
    cause mechanical stresses...
    It all depends on your design.. look at a piezo disc buzzer
    it has both electrical contacts on top... whereas some
    quartz crystals have contacts on opposite physical sides of
    a slab of material... it just depends on your application's
    design requirements.

    What are you making, in what volumes, and what
    are the primary design criteria?
     
  5. Jul 22, 2007 #4

    xez

    User Avatar

Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?



Similar Discussions: Highly Efficient Piezoelectric Ceramics
Loading...