We are trying to measure the d33 coefficient of a large organic crystals and I was wondering whether or not PFM would be the method to go for. I see that generally thin films of the samples are being used for PFM applications but in our case, our samples are large crystals/grains with no flat surface finish.
Would PFM work for our samples? If so, is there any specific sample prep that we need to be aware of? If not, which method/technique should we go for?
Completely new to this area and any suggestions would greatly be appreciated.
Thanks,
-Metin
Merhaba Metin,
I think there is no reason to not to use PFM even for large samples. Nevertheless, the zone probed by the PFM tip is very small compared to your whole sample. The signal creaed by PFM is then a local piezoelectric response of your sample. You need probably to scan all your sample surface which can demand some time.
I am not sure about the dimensions of your sample but for starting, you can do a simple experience : apply a force on your sample and try to detect the signal of the d33 direction by putting the concductive electrodes on the appropriate surface of your sample.
Best regards
Merhaba @Atilla Hocam,
Thanks you for your answer. We have done some preliminary testing on our, relatively, smaller organic crystals (400-500 microns). We have seen that the piezoresponse acquired from different regions of the surface resulted in extensive variations, 10 even 20 fold differences. We see this behavior especially on rough surfaces rather than flat sections.
We plan to have a better surface finish and give it a shot again. I will appreciate if you could have any further suggestions, though.
Thank you,
Regards,
-Metin
The best method to measure d33 is to use a Berlincourt tester. The piezoelectric charge coefficient, d33 (and others), is one of the fundamental parameters defining the piezoelectric activity of a material. This direct method was developed by physician-physicist Don Berlincourt, in 1971; and fortunately, the piezoelectric charge coefficient is relatively easy to measure. It is measured by applying an oscillating force to a sample and measuring the charge that is generated.
The derivation of the piezoelectric charge coefficient equation involves measuring the charge, strain and displacement and dividing the values obtained, or, since the dimensional terms drop out, simply measuring the charge developed and the force applied will yield the piezoelectric charge coefficient, d33, typically in units of pC/N. From the d33 and permittivity, the stress coefficient can be derived.
The nice thing about this method is that it can use any thickness for the test material. I have measured samples as thick as a centimeter and as thin as 2 micrometers.
Thank you, Henry Savage !
Regarding to the d33 measurements using Berlincourt tester, as far as I could see, the literature lists many examples of sintered ceramic/ceramic composites and etc. Generally powders are synthesized first and then they are sintered to obtain a dense, solid sample.
Do you think that we can test powders or particles with this method (as long as we could clamp the powders between force heads in the tester)? Our samples are generally organic crystals with 300-400 microns and they have an irregular morphology. Sorry if this is a dumb question, I am new to this area.
Thank you,
-Metin
No, the powder needs to be in a made into a sintered ceramic plate, bar or disk of some kind and then poled, before it will exhibit piezoelectricity. The charge domains will be randomly oriented with a net neutral charge until poled. After poling you can measure d33.
I've included a large section on poling in my textbook, "Ultrasound & Piezoelectric Physics for Engineers: A Primer with Applications and Examples". Most of the piezoelectric section is for piezoelectric polymers, but piezoceramics are included.
https://www.amazon.com/Ultrasound-Piezoelectric-Physics-Engineers-Applications/dp/1793995389/ref=tmm_pap_swatch_0?_encoding=UTF8&qid=1563502186&sr=8-1
In PFM, when we apply the bias one end is the tip and what is the other end?
(When we are measuring PFM of our material taken on a glass substrate.)
- Badges
- Science topic
- Similar topics
- Physical Sciences
- Materials Science
- Materials
- Composites
- Nanocomposites