Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Unusual Ceramics Could Expand Possibilities For Superconductors

26.06.2002


Ceramic materials with "split personalities" could lead to new high-temperature superconductors, according to physicists at Ohio State University and their colleagues.



Researchers here have learned that these ceramic materials, called cuprates (pronounced KOOP-rates), switch between two different kinds of superconductivity under certain circumstances.

The finding could settle a growing controversy among scientists and point the way to buckyball-like superconductivity in ceramics.


Scientists have been arguing for years whether cuprates exhibit one type of superconductivity, called d-wave, or another type, called s-wave, explained Thomas Lemberger, professor of physics.

The difference depends on how the electrons are arranged within the material, he said. Materials with s-wave behavior are more desirable, because they should have better technical properties at high temperatures. Unfortunately, most of the high-temperature cuprate compounds seem to exhibit d-wave behavior. S-wave superconductivity at high temperatures is still a possibility and is a goal of current research, Lemberger said.

For instance, buckyballs -- soccer-ball-shaped carbon molecules discovered at Bell Labs in 1991 -- exhibit s-wave superconductivity at 40° Kelvin (-388°F, -233°C), a very high temperature for superconductors. To achieve this, the Bell Labs scientists mixed, or "doped," the buckyballs with potassium.

Now Lemberger and his colleagues have found they can change the behavior of a certain class of cuprates from d-wave to s-wave if they dope it with sufficient amounts of the element cerium -- a common ingredient in glassware.

"It seems that the mechanisms for both kinds of behavior are always present in these materials," Lemberger said. "So if you do something to suppress one behavior, a cuprate will automatically switch to the other."

They report their results in two papers in a recent issue of the journal Physical Review Letters. Lemberger, doctoral student John Skinta and postdoctoral researcher Mun-Seog Kim collaborated with Tine Greibe and Michio Naito, both materials scientists at NTT Basic Research Laboratories in Japan.

Since their discovery in 1986, cuprates have puzzled scientists. Ceramics are normally insulators, but when doped with atoms of elements like lanthanum or cerium, cuprates suddenly become excellent conductors.

"That’s what’s so amazing about these materials," Lemberger said. "A cuprate could start out as a very good insulator; you could subject it to thousands of volts and it won’t conduct electricity at all. But change the composition just a little, and you’ve turned it into a superconductor. With the tiniest wisp of voltage, you’ll get huge currents flowing."

Normal doping involves adding small quantities of a secondary material in order to boost the number of mobile electrons in a sample. Over-doping, as the Ohio State physicists and their colleagues did, is roughly equivalent to over-stuffing the material with electrons -- as many electrons as the cuprate would hold while still maintaining its unique crystal structure.

They created thin films of cuprates with different amounts of cerium, and studied how the electrons arranged themselves within the material. They did this by measuring how deeply a magnetic field could penetrate each film.

As the researchers pushed the cerium content of the cuprates to the limit, the magnetic field measurements suggested that the electrons had changed their formation from d-wave to s-wave.

Scientists have speculated that cuprates could sustain s-wave superconductivity at temperatures as high as 90° Kelvin
(-298°F, -183°C). That would make the materials useful conductors for commercial electronics. If metal conductors were replaced with superconducting ceramics, devices would be more efficient, and new types of devices would become possible. And 90° Kelvin, while very cold, is still easier and less expensive to achieve than 10° Kelvin (-442°F, -263°C), the operating temperature of conventional metallic superconductors.

Lemberger said the scientific controversy surrounding the nature of superconductivity in cuprates will come to a head this summer, as researchers gather in Taiwan to debate which of the two "personalities," d-wave or s-wave, is the true state of the material.

"Our work bridges the gap between the two camps," Lemberger said. "We propose that it’s just a matter of composition."

"The question now is, how high can we push s-wave superconductivity?" he added.

The National Science Foundation funded this work.


Contact: Thomas Lemberger, (614) 292-7799; Lemberger.1@osu.edu

Written by Pam Frost Gorder, (614) 292-9475; Gorder.1@osu.edu

Thomas Lemberger | EurekAlert!
Further information:
http://prl.aps.org/
http://www.nsf.gov/

More articles from Physics and Astronomy:

nachricht Smooth propagation of spin waves using gold
26.06.2017 | Toyohashi University of Technology

nachricht A 100-year-old physics problem has been solved at EPFL
23.06.2017 | Ecole Polytechnique Fédérale de Lausanne

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Can we see monkeys from space? Emerging technologies to map biodiversity

An international team of scientists has proposed a new multi-disciplinary approach in which an array of new technologies will allow us to map biodiversity and the risks that wildlife is facing at the scale of whole landscapes. The findings are published in Nature Ecology and Evolution. This international research is led by the Kunming Institute of Zoology from China, University of East Anglia, University of Leicester and the Leibniz Institute for Zoo and Wildlife Research.

Using a combination of satellite and ground data, the team proposes that it is now possible to map biodiversity with an accuracy that has not been previously...

Im Focus: Climate satellite: Tracking methane with robust laser technology

Heatwaves in the Arctic, longer periods of vegetation in Europe, severe floods in West Africa – starting in 2021, scientists want to explore the emissions of the greenhouse gas methane with the German-French satellite MERLIN. This is made possible by a new robust laser system of the Fraunhofer Institute for Laser Technology ILT in Aachen, which achieves unprecedented measurement accuracy.

Methane is primarily the result of the decomposition of organic matter. The gas has a 25 times greater warming potential than carbon dioxide, but is not as...

Im Focus: How protons move through a fuel cell

Hydrogen is regarded as the energy source of the future: It is produced with solar power and can be used to generate heat and electricity in fuel cells. Empa researchers have now succeeded in decoding the movement of hydrogen ions in crystals – a key step towards more efficient energy conversion in the hydrogen industry of tomorrow.

As charge carriers, electrons and ions play the leading role in electrochemical energy storage devices and converters such as batteries and fuel cells. Proton...

Im Focus: A unique data centre for cosmological simulations

Scientists from the Excellence Cluster Universe at the Ludwig-Maximilians-Universität Munich have establised "Cosmowebportal", a unique data centre for cosmological simulations located at the Leibniz Supercomputing Centre (LRZ) of the Bavarian Academy of Sciences. The complete results of a series of large hydrodynamical cosmological simulations are available, with data volumes typically exceeding several hundred terabytes. Scientists worldwide can interactively explore these complex simulations via a web interface and directly access the results.

With current telescopes, scientists can observe our Universe’s galaxies and galaxy clusters and their distribution along an invisible cosmic web. From the...

Im Focus: Scientists develop molecular thermometer for contactless measurement using infrared light

Temperature measurements possible even on the smallest scale / Molecular ruby for use in material sciences, biology, and medicine

Chemists at Johannes Gutenberg University Mainz (JGU) in cooperation with researchers of the German Federal Institute for Materials Research and Testing (BAM)...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Plants are networkers

19.06.2017 | Event News

Digital Survival Training for Executives

13.06.2017 | Event News

Global Learning Council Summit 2017

13.06.2017 | Event News

 
Latest News

Study shines light on brain cells that coordinate movement

26.06.2017 | Life Sciences

Smooth propagation of spin waves using gold

26.06.2017 | Physics and Astronomy

Switchable DNA mini-machines store information

26.06.2017 | Information Technology

VideoLinks
B2B-VideoLinks
More VideoLinks >>>