Posted on 09/21/2010 8:50:31 AM PDT by decimon
Washington, D.C. (September 21, 2010) -- For months, Anthony West could hardly believe what he and his colleagues were seeing in the lab -- or the only explanation for the unexpected phenomena that seemed to make sense.
Several of the slightly doped high-purity barium titanate (BT) ceramics his research group was investigating were not following the venerable Ohm's Law, which relates electrical voltage to current and resistance. Applying or removing a voltage caused a gradual change in the materials' electrical resistance. The new effect was seen consistently regardless of the temperature or whether the experiments were conducted in vacuum, air, or in an oxygen atmosphere. The time to stabilize and the final, steady-state resistance were, however, both temperature-dependent.
"I was not immediately convinced myself about the non-Ohm's Law behavior," said West, Professor of Electroceramics and Solid State Chemistry at the University of Sheffield in England. "Interfacial effects are well known for their non-Ohmic behavior. We needed to be really convinced that our results were not influenced in some way by interfacial effects."
West's proposed mechanism for the non-Ohm behavior is also unconventional: the ionization of only one of the two extra electrons from oxygen atoms that are attached to dopant atoms. This process leaves behind a positively charged "hole" that can move fairly readily in what is called a hole current. West and his colleagues at Sheffield and the Universidat Jaume 1 in Castellon, Spain, described their latest experiments with calcium-doped BT in the journal Applied Physics Letters, which is published by the American Institute of Physics. Similar results with zinc and magnesium dopants were published earlier this year in other technical journals. Calcium, zinc and magnesium are known as "acceptor" dopants, which can promote hole currents.
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Undoped BT and "donor"-doped materials did not exhibit this unusual behavior. West believes that these results may ultimately lead to a better understanding of how ceramics used in electrical circuits degrade and may possibly even stimulate new insights into high-temperature superconductivity mechanisms in oxide ceramics.
The article, "Field enhanced bulk conductivity of acceptor-doped BaTi1-xCaxO3-x ceramics" by Nahum Maso, Marta Prades, Hector Beltran, Eloisa Cordoncillo, Derek C. Sinclair, and Anthony R. West appears in the journal Applied Physics Letters. See: http://link.aip.org/link/applab/v97/i6/p062907/s1
Journalists may request a free PDF of this article by contacting jbardi@aip.org
ABOUT APPLIED PHYSICS LETTERS
Applied Physics Letters, published by the American Institute of Physics, features concise, up-to-date reports on significant new findings in applied physics. Emphasizing rapid dissemination of key data and new physical insights, Applied Physics Letters offers prompt publication of new experimental and theoretical papers bearing on applications of physics phenomena to all branches of science, engineering, and modern technology. Content is published online daily, collected into weekly online and printed issues (52 issues per year). See: http://apl.aip.org/
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The American Institute of Physics is a federation of 10 physical science societies representing more than 135,000 scientists, engineers, and educators and is one of the world's largest publishers of scientific information in the physical sciences. Offering partnership solutions for scientific societies and for similar organizations in science and engineering, AIP is a leader in the field of electronic publishing of scholarly journals. AIP publishes 12 journals (some of which are the most highly cited in their respective fields), two magazines, including its flagship publication Physics Today; and the AIP Conference Proceedings series. Its online publishing platform Scitation hosts nearly two million articles from more than 185 scholarly journals and other publications of 28 learned society publishers.
Temperature dependent....Opps.
caused a gradual change in the materials’ electrical resistance.
So Delta V = I * Delta R.
How is Ohm’s law repealed?
self changing potentiometer? Wouldn’t violate Ohm’s law.
Oxides are on dope now? No wonder they are breaking the law!
Sounds like a non-linear device in which the “resistance” they are using in their calculation varies with time and temperature.
A more meaningful discovery would be to violate Kirchhoff’s law
Sounds somewhat like a posistor/thermistor.
Yeah, I didn’t see any violation,
just a change in resistance as voltage was applied,
resulting in an Ohm’s law correspondent change in current...
This is much ado about nothing. Sure, maybe we have a new form of semiconuctor, but I don’t see where Ohm’s Law is violated.
As someone said previously, if Kirchoff’s voltage law and current law somehow don’t work anymore. then we have something here to get excited about.
Doesn’t a diode do the same thing?
i.e. change resistance depending upon the voltage applied.
A zener diode does, after the reverse “breakdown” voltage is hit.
A regular diode just allows current in one direction.
Or a rejustor.
http://www.mbridgetech.com/
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BUT..... does the resistance go DOWN, or UP, when the temperature goes UP ???
It it goes down, I see why they are excited.
Regular diode
Resistance about 0 when voltage at one polarity.
Resistance about infinite when voltage at the opposite polarity.
But yea a zener is a better comparison.
Barium titanates are already used commercially for microphones. This article needs to get to the point.
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