Crystal Power CeLL by John Hutchison

[sutra]

I've prepared some Rochelle salt and I did melt it in the microwave without any strange fenomenon...after solidification, the material has a waxy-sticky consistence...I just added water then to allow crystallisation.....I didn't test its characteristics but i belive that in amorfous solidification, it may loose it's piezoelectric properties...

I read that Rochelle salt melts at 75 C.
I am wondering if it is still piezoelectric after it's been melted and then left to solidify.
Anyone know the answer to this question?Ã,  I haven't been able to find any info on it.
If it can be melted and then solidified again it can be shaped.

[Feynman]

Another chemist want to comment on the rochelle salt piezoelectricity?

As for sodium carbonate production, I cannot find the link.  So perhaps it is best to acquire sodium carbonate reagent for pool pH equalization.

[ian middleton]

G'Day all,
@Feynman:
Sodium Carbonate is washing soda. Arm and Hammer sell it. Sometimes it is called laundry soda.


@sutra: when you melted the rochelle salt in the microwave was the salt dry or moist?
If you heat rochelle salt too much it will become amorphous. Dissolve in water and evapourate slowly to retrieve clear crystals.
Not sure how excessive heat effects the piezoelectricty of the crystals but when I get some I'll find out.

All the best

Ian

[Koen1]

Not very much to comment on really...
What is there you want to know about it and cannot find?

Piezoelectric effect is always due to the crystalline structure of the material.
Rochelle salt is a Na/K-tatrate, can be made by reacting two ingredients as was
already quite adequately explained in that link provided by AbbaRue, but
can also simply be bought. It is not expensive at all, and should be easy to
order from a shop or website that sells common chemicals.
If you have trouble finding it, you may want to search for its other name
"Seignette salt", or simply "potassium sodium tartrate".
Since it is used in the food industry as a preservative and additive,
you might be able to find it with suppliers of food additives, as E337.

But perhaps it is worth knowing that although it is piezoelectric,
several much more piezoelectrically active materials have been
developed. Quartz is also piezoelectric, as is barium titanate,
and actually there are quite a number of piezoelectric
compound materials that can be made. For a historic perspective
it may be interesting that one of the old 1940s electrophysics
books in my collection very clearly states that rochelle salts
can be used to generate a piezoelectric effect, in more modern
piezo elements barium titanate is used to greater effect. Hehe,
yes, obviously the "modern" relates to the 1940s...
There are even better ones nowadays, but barium titanate is
still used for many if not most piezo uses. Except for the
piezo oscillator components, those are most often quartz.

But remember: piezoelectric effect has to do with pressure differences.
So there need to be pressure differences or kinetic shocks for the
material to produce output.
Just like the pyroelectric effect of tourmaline needs a temperature
difference or constant temperature fluctuations to produce output.
You can make a neat looking cell of piezo material but it won't do
much without input shocks or pressure fluctuations, and similarly
you can make a really neat pyroelectric cell but you'll need to have
a fluctuating heat source to get anything usefull out.

[Feynman]

Thanks Koen.  Yes I agree piezoelectric is a pressure effect.


But perhaps there is something more, like the Casimir effect?

http://en.wikipedia.org/wiki/Casimir_effect