Forum für Wissenschaft, Industrie und Wirtschaft

Hauptsponsoren:     3M 
Datenbankrecherche:

 

Why Calcium Improves a High-Temperature Superconductor

08.06.2004


Scientists at the U.S. Department of Energy’s Brookhaven National Laboratory have found evidence to prove why adding a small amount of calcium to a common high-temperature superconductor significantly increases the amount of electric current the material can carry. This research may be a first step toward developing commercial applications for high-temperature superconducting materials. The results appear in the May 15, 2004 issue of Physical Review Letters.


Yimei Zhu (left) and Marvin Schofield, in front of the transmission electron microscope they used to perform the research



“Many materials classified as high-temperature superconductors exhibit good properties only in single-crystal form and are actually unsuitable for practical applications, such as high-efficiency electrical wire, because their bulk composition – individual crystalline grains – disrupts the flow of electrons,” said Yimei Zhu, a Brookhaven physicist who led the research.

... mehr zu:
»Science »Why »YBCO


“But for practical applications in which large electric currents need to be transported, such as power cables, the polycrystalline forms must be used. These polycrystalline materials carry a very low current compared to their single-crystal counterparts,” he said.

This is due to the problem of grain boundaries – the interfaces created between adjacent grains. At grain boundaries, incoming electrons slow down or change direction, thus losing momentum and releasing the lost energy as heat. This results in low electron flow across the boundaries – exactly the opposite of “good” superconductor behavior.

Researchers theorized that electric voltage barriers at the grain boundaries are the cause of this problem. Now, the Brookhaven scientists have found evidence to support this theory.

“We discovered why grain boundaries are the predominant factor that limits the current flow in these materials,” said Brookhaven physicist Marvin Schofield, the paper’s principle author.

“By understanding grain boundary behavior, we can engineer grain boundaries with improved properties. This is a major challenge in superconductor research, which may lead to the commercialization of high-temperature superconducting materials that could revolutionize our daily lives in the near future.”

Scientists worldwide have studied YBCO, a high-temperature superconductor named for the elements it contains – yttrium, barium, copper, and oxygen. They know that it conducts significantly better when it is “doped” with calcium, but have not known, until now, why this is true. The Brookhaven scientists determined this by comparing calcium-doped YBCO to undoped YBCO.

The evidence lies in the areas within grain boundaries in which adjacent grains are most mismatched. To visualize this, picture a centimeter-based ruler next to an inch-based one, where the tick marks on each ruler represent the positions of atoms in the crystal structure of two adjacent, slightly different grains. The marks will match in some cases, nearly match in others, and misalign completely in the rest.

In undoped YBCO, the scientists found, the electrons encounter the most electrical resistance at the most misaligned regions, where the voltage barrier is wide and high. Doping YBCO with calcium causes these regions to shrink, both in width and height. As a result, Schofield and his colleagues determined that calcium doping increases the current across the grain boundary by 35 percent.

To perform the research, the Brookhaven scientists used a YBCO “bicrystal,” a type of crystal grown to contain just one grain boundary, much like two very large grains merged together. The electromagnetic properties of bicrystals are well characterized, allowing the researchers to pinpoint what happens to the electrons at the boundary upon calcium doping, using the results as a model for the overall material. Bicrystals eliminate the impossible task of isolating one boundary out of thousands in the material sample.

To closely examine the bicrystal grain boundary, the scientists used a transmission electron microscope (TEM), a device that uses electrons as tiny probes to “see” inside materials. A sample is placed inside the TEM and bombarded with electrons. As the electrons pass through the sample, they are scattered away from the charged regions of the material. When they emerge, they carry information about the electric and magnetic fields within the sample. This information is then retrieved by a method known as electron holography.

“With electron holography,” Schofield explained, “we can see exactly what the electrons in the material see at the grain boundary. Thus, this method takes us a tremendous step closer to understanding the role grain boundaries play in the properties of real materials.”

Additional collaborators instrumental in this research were Marco Beleggia, of Brookhaven Lab, and Karsten Guth and Christian Jooss, both of the University of Gottingen in Germany. The work was funded by the Office of Basic Energy Sciences within the U.S. Department of Energy’s Office of Science and the German Research Foundation.

Karen McNulty Walsh | BNL
Weitere Informationen:
http://www.bnl.gov/bnlweb/pubaf/pr/2004/bnlpr060704.htm

Weitere Berichte zu: Science Why YBCO

Weitere Nachrichten aus der Kategorie Materialwissenschaften:

nachricht Hält die Klebung?
29.05.2017 | Technische Hochschule Mittelhessen

nachricht Wussten Sie, dass Verpackungen durch Flash Systeme intelligent werden?
23.05.2017 | Heraeus Noblelight GmbH

Alle Nachrichten aus der Kategorie: Materialwissenschaften >>>

Die aktuellsten Pressemeldungen zum Suchbegriff Innovation >>>

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

Im Focus: Neue Methode zur Charakterisierung von Graphen

Wissenschaftler haben eine neue Methode entwickelt, um die Eigenschaften von Graphen ohne das Anlegen störender elektrischer Kontakte zu charakterisieren. Damit lassen sich gleichzeitig der Widerstand und die Quantenkapazität von Graphen sowie von anderen zweidimensionalen Materialien untersuchen. Dies berichten Forscher vom Swiss Nanoscience Institute und Departement Physik der Universität Basel im Wissenschaftsjournal «Physical Review Applied».

Graphen besteht aus einer einzigen Lage von Kohlenstoffatomen. Es ist transparent, härter als Diamant, stärker als Stahl, dabei aber flexibel und ein deutlich...

Im Focus: New Method of Characterizing Graphene

Scientists have developed a new method of characterizing graphene’s properties without applying disruptive electrical contacts, allowing them to investigate both the resistance and quantum capacitance of graphene and other two-dimensional materials. Researchers from the Swiss Nanoscience Institute and the University of Basel’s Department of Physics reported their findings in the journal Physical Review Applied.

Graphene consists of a single layer of carbon atoms. It is transparent, harder than diamond and stronger than steel, yet flexible, and a significantly better...

Im Focus: Detaillierter Blick auf molekularen Gifttransporter

Transportproteine in unseren Körperzellen schützen uns vor gewissen Vergiftungen. Forschende der ETH Zürich und der Universität Basel haben nun die hochaufgelöste dreidimensionale Struktur eines bedeutenden menschlichen Transportproteins aufgeklärt. Langfristig könnte dies helfen, neue Medikamente zu entwickeln.

Fast alle Lebewesen haben im Lauf der Evolution Mechanismen entwickelt, um Giftstoffe, die ins Innere ihrer Zellen gelangt sind, wieder loszuwerden: In der...

Im Focus: Neue Methode für die Datenübertragung mit Licht

Der steigende Bedarf an schneller, leistungsfähiger Datenübertragung erfordert die Entwicklung neuer Verfahren zur verlustarmen und störungsfreien Übermittlung von optischen Informationssignalen. Wissenschaftler der Universität Johannesburg, des Instituts für Angewandte Optik der Friedrich-Schiller-Universität Jena und des Leibniz-Instituts für Photonische Technologien Jena (Leibniz-IPHT) präsentieren im Fachblatt „Journal of Optics“ eine neue Möglichkeit, glasfaserbasierte und kabellose optische Datenübertragung effizient miteinander zu verbinden.

Dank des Internets können wir in Sekundenbruchteilen mit Menschen rund um den Globus in Kontakt treten. Damit die Kommunikation reibungslos funktioniert,...

Im Focus: Strathclyde-led research develops world's highest gain high-power laser amplifier

The world's highest gain high power laser amplifier - by many orders of magnitude - has been developed in research led at the University of Strathclyde.

The researchers demonstrated the feasibility of using plasma to amplify short laser pulses of picojoule-level energy up to 100 millijoules, which is a 'gain'...

Alle Focus-News des Innovations-reports >>>

Anzeige

Anzeige

IHR
JOB & KARRIERE
SERVICE
im innovations-report
in Kooperation mit academics
Veranstaltungen

Wissenschaftsforum Chemie 2017

30.05.2017 | Veranstaltungen

Erfolgsfaktor Digitalisierung

30.05.2017 | Veranstaltungen

Lebensdauer alternder Brücken - prüfen und vorausschauen

29.05.2017 | Veranstaltungen

 
VideoLinks
B2B-VideoLinks
Weitere VideoLinks >>>
Aktuelle Beiträge

Neue Methode zur Charakterisierung von Graphen

30.05.2017 | Physik Astronomie

Riesenfresszellen steuern die Entwicklung von Nerven und Blutgefäßen im Gehirn

30.05.2017 | Biowissenschaften Chemie

Nano-U-Boot mit Selbstzerstörungs-Mechanismus

30.05.2017 | Biowissenschaften Chemie