Polymers as semi-Metals

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seasmith
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Joined: Thu Mar 27, 2008 6:59 pm

Polymers as semi-Metals

Unread post by seasmith » Mon Dec 09, 2013 5:36 pm

Polymers can be semi-Metals

Traditional plastics, or polymers, are electrical insulators.
A few years ago Xavier Crispin discovered that conductive polymers can be thermoelectric. A thermoelectric material undergoes a diffusion of electronic charge carriers to the cold region when the material is submitted to a temperature gradient.
As a result an electric potential is created between the cold and hot side of the material. This thermo-voltage is the basis of thermo-couples used for instance in an everyday oven thermometer….
the polymer, in this case a doped variant of the plastic PEDOT, behaves exactly like a semimetal, which also explains the high Seebeck effect.
Thermoelectric generators are available on the market today, but these are made from alloys of bismuth and the semimetal tellurium. Unlike the polymers, these elements are both rare and expensive.
The N-P doping of semiconductors (here for heat/charge conversion) seems analog to the insertion of defects (usually N2 vacancies) in diamond nano-wires for light/charge conversions.

http://www.nanowerk.com/nanotechnology_ ... a3_991.jpg

Sparky
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Joined: Tue Jul 20, 2010 2:20 pm

Re: Polymers as semi-Metals

Unread post by Sparky » Thu Jan 09, 2014 9:31 am

Defining: :D

:shock:
PEDOT
3,4-ethylenedioxythiophene ... :shock:
"Pedot" means "Beasts" in Finnish. ;)
semi-Metals
--elements that have properties of both metals and nonmetals. :? \\
A thermoelectric module (thermo-module) consists of P and N semiconductor elements and ceramic substrates. In appearance, it is a unit in which pairs of elements are sandwiched between ceramic substrates, and the elements are electrically series-connected, P-N, P-N. Its size is generally 10-40 mm square and 3-6 mm thick. Heat is absorbed from one side of the module and pumped to the other side while applying direct current, so that the temperature is precisely controlled.
Demand for thermo-modules is growing significantly - one factor is the growth of fiber-optic networks accompanied by development of IT utilization.
Laser diodes for fiber-optic networks need temperature control so that the light wavelength stays constant in order to make a stable signal transduction. The light wavelength strongly correlates to the diode temperature. That's why thermo-modules are needed.
The
Seebeck effect
is transduction of temperature difference to electricity.



Image
behaves exactly like a semimetal
errr, does this really say anything? :D
semimetals: elements that have properties of both metals and nonmetals. :? \\
"It is dangerous to be right in matters where established men are wrong."
"Doubt is not an agreeable condition, but certainty is an absurd one."
"Those who can make you believe absurdities, can make you commit atrocities." Voltaire

seasmith
Posts: 2815
Joined: Thu Mar 27, 2008 6:59 pm

Re: Polymers as semi-Metals

Unread post by seasmith » Fri Jan 10, 2014 9:58 pm

behaves exactly like a semimetal

errr, does this really say anything? :D
semimetals: elements that have properties of both metals and nonmetals.

Metals are good conductors of heat/electricity and are ductile/malleable. Non-metals the opposite.

Metals have those attributes primarily due to atomic alignment, i.e. lattice structures of their atoms, which also accounts for a material surface which is reflective, or 'lustrous' .

In the case of the new polymers, metallic qualities are induced by N-P doping, like in a transistor.

The common denominator seems to be the ability of an element or molecule to conduce the through-transmission of charge, as opposed to the universal and ever present re-cycling and diffusion of charge. (The chemists out there will no doubt have a more erudite explanation)

That putative common denominator is what prompted me to post the article.
[and the future possibility of plastic toasters]

Sparky
Posts: 3517
Joined: Tue Jul 20, 2010 2:20 pm

Re: Polymers as semi-Metals

Unread post by Sparky » Sat Jan 11, 2014 9:41 am

Thanks for clarification..... ;)

I come into many threads with only limited understanding of various subjects being brought forth, so I usually don't try to respond beyond what has been posted. :oops:
"It is dangerous to be right in matters where established men are wrong."
"Doubt is not an agreeable condition, but certainty is an absurd one."
"Those who can make you believe absurdities, can make you commit atrocities." Voltaire

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