Materials Science undergrad here.

Don't know whether I'm in the right section but, I wonder if you guys have any experience or have research done in the field of Piezoelectric ceramics?

My research is confined to BT and BNT ceramics due to economic factors but I'm open to any new ideas in the field...

Hi!

As far as possible, ceramics are replaced by PVDF.
This plastic is not directly piezoelectric, but is ferroelectric: is remains electrically polarized after receiving an intense electric field (as would a permanent magnet do with induction, hence the named coined from "ferromagnetic"). Once polarized, it acts as a piezoelectric material.

PVDF has many advantages: its "piezoelectric" constants are much better than ceramics' ones, especially the deformations are bigger since it's a plastic. And its lower acoustic impedance matches water better, and is easier to match to air. It's also resilient and nontoxic.

Many years ago, engineering documentation (for beepers etc) from Murata, TDK and other ceramic components suppliers had a few pages with data about the materials, and very interesting also, how the components were designed - since coupling a ceramic to air is a challenge due to the impedance mismatch.

Thanks for the prompt reply Enthalpy.

A quick look at PVDP in wikipedia told me that piezoelectric constant in PVDP is about 6-7 pCN-1.

But according to my lit survey I've found the constant of PZT to in the range of 43-223pC/N. Even in BZT I've found literature claiming values of 147 pC/N.

Is there something to it that I'm overseeing?

This value is only a part of the conversion efficiency.

You have a force and a displacement on one side, a charge and a voltage on the other.

If you're interested in the amount of electric energy that is converted in mechanical energy (or the other way), you must also look at the voltage and the strain, and then PVDF is better than ceramics.

Also, its mechanical impedance can be easier to match, and PVDF is easily milled, turned or pressed into complicated forms, which a ceramic can't. Resilient and cheap as well.

There are medicinal usages for piezoelectric pens, for example. Pop the pen on your hands in given known spots for acupuncture purposes and you open up a field of applications.

Since there seems to be a conflict of opinion, I imagined it would be best to test out the materials and benchmark them on my own. Since our department has a LCR lying around, this made it quite easy.

So I'm posting the experimental Cp values that I got using different AC frequencies of laboratory sintered ceramics (mixed-oxide method) and commercial grade PVDF-TrFE.

Frequency----BaTiO3--------- Ba0.5Sr0.5TiO3 --------PVDF-TrFE
50 Hz ------- 551.88 PF -----------748.37 --------------183.45 PF
100 Hz ----- 497.55 PF -----------711.82 PF----------- 181.95 PF
1 kHz-------- 377.25 PF-----------576.29 PF----------- 177.59 PF
10 kHz-------347.34 PF----------- 583.88 PF-----------172.69 PF
100 kHz------332.29 PF----------519.68 PF------------161.07 PF



clearly BT has 5 times the capacitance of PVDF. Which of course doesn't say anything about piezoelectricity. But traditionally we expect higher piezoelectricity, when the polarizability is high. Thus minus points for PVDF so far.

Now, about this mechanical impedance thing... Is there a way to test it in lab scale?

Best,
~R

Waisting my time.

Stick with my idea and you should be able to spin product.