Featured Research

from universities, journals, and other organizations

Researchers image atomic structural changes that control properties of sapphires

Date:
November 25, 2010
Source:
Case Western Reserve University
Summary:
Researchers have imaged the change in atomic structure of sapphire that had undergone deformation at high temperatures. In crystalline materials, these changes control electrical, magnetic and chemical properties as well as strength and durability.

Materials scientists from Case Western Reserve University and the Institute of Solid State Research in Jülich, Germany have produced particularly clear changes in the atomic structure of sapphire following deformation at high temperatures.

Related Articles


Peering through an electron microscope down to a level where a human hair would seem as wide as a washer and dryer set, they were able to quantify deviations from the regular columns of aluminum and oxygen atoms -- the stuff of perfect sapphire crystals. The work will be published in the journal Science.

These structural changes are called dislocations and include very small rearrangements of some of the aluminum atoms from their normal surroundings of six oxygen atoms to a layout of four surrounding oxygen atoms.

While the changes in structure are minute, they deliver a punch.

In the orderly world of crystals, dislocations can control electrical, chemical and magnetic properties as well as strength and durability. And, the information and imaging technique used in the study can be applied to all crystalline solids, from microchips to thermal protection systems that shield jet engines from extreme heat.

"We imagined this might have been the possible change in structure a year or so ago and now we're able to see how the atoms are moving with respect to one another," said Arthur Heuer, Distinguished University Professor and Kyocera Professor of Ceramics in the department of materials science and engineering at the Case School of Engineering. "The important thing is we were able to image it with atomic resolution."

Peter Lagerlöf, an associate professor of materials science and engineering at Case Western Reserve, noted that "understanding the structure of the dislocations is important because it allows increased understanding of material properties."

Heuer traveled to Julich, Germany, where he worked with Chunlin Jia at the Institute of Solid State Research and Ernst Ruska-Centre for Electron Microscopy. There, using an ultra high magnification transmission electron microscope, the scientists employed negative spherical aberration imaging to a section of synthetic sapphire to see dislocation cores.

This is the first time the technique was applied at subangstrom resolution to structural defects in ceramics.

The scientists were able to distinguish columns of oxygen from columns of aluminum in synthetic sapphire, used to make substrates for specialty advanced computer chips (because of sapphire's good thermal conductivity and electrical resistivity), and grocery store scanners and expensive watch faces (because of sapphire's superior scratch-resistance compared to glass).

Dislocation cores terminate with aluminum atoms and electrical neutrality is maintained as the cores occupy only half of the aluminum sites. A complex mix of six-fold and four-fold coordinated aluminum polyhedra are found in the dislocation cores.

Jacques Castaing, a materials scientist at Laboratorie Physique des Materiaux, CNRS Bellevue, F 92195 Meudon Cedex, France, was not involved in the experiment but with Heuer and Lagerlöf, last year published a theory that the atomic structure would change this way.

Castaing said that being able to see the dislocations, "for the basic knowledge of materials, is very important. These dislocations are everywhere."


Story Source:

The above story is based on materials provided by Case Western Reserve University. Note: Materials may be edited for content and length.


Journal Reference:

  1. A. H. Heuer, C. L. Jia, K. P. D. Lagerlöf. The Core Structure of Basal Dislocations in Deformed Sapphire (α-Al2O3). Science, 2010; 330 (6008): 1227-1231 DOI: 10.1126/science.1192319

Cite This Page:

Case Western Reserve University. "Researchers image atomic structural changes that control properties of sapphires." ScienceDaily. ScienceDaily, 25 November 2010. <www.sciencedaily.com/releases/2010/11/101125202005.htm>.
Case Western Reserve University. (2010, November 25). Researchers image atomic structural changes that control properties of sapphires. ScienceDaily. Retrieved November 21, 2014 from www.sciencedaily.com/releases/2010/11/101125202005.htm
Case Western Reserve University. "Researchers image atomic structural changes that control properties of sapphires." ScienceDaily. www.sciencedaily.com/releases/2010/11/101125202005.htm (accessed November 21, 2014).

Share This


More From ScienceDaily



More Matter & Energy News

Friday, November 21, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Toyota's Hydrogen Fuel-Cell Green Car Soon Available in the US

Toyota's Hydrogen Fuel-Cell Green Car Soon Available in the US

AFP (Nov. 21, 2014) — Toyota presented its hydrogen fuel-cell compact car called "Mirai" to US consumers at the Los Angeles auto show. The car should go on sale in 2015 for around $60.000. It combines stored hydrogen with oxygen to generate its own power. Duration: 01:18 Video provided by AFP
Powered by NewsLook.com
NSA Director: China Can Damage US Power Grid

NSA Director: China Can Damage US Power Grid

AP (Nov. 20, 2014) — China and "one or two" other countries are capable of mounting cyberattacks that would shut down the electric grid and other critical systems in parts of the United States, according to Adm. Michael Rogers, director of the National Security Agency and hea Video provided by AP
Powered by NewsLook.com
Latest Minivan Crash Tests Aren't Pretty

Latest Minivan Crash Tests Aren't Pretty

Newsy (Nov. 20, 2014) — Five minivans were put to the test in head-on crash simulations by the Insurance Institute for Highway Safety. Video provided by Newsy
Powered by NewsLook.com
Takata Offers "sincerest Condolences" To Victims of Malfunctioning Airbag

Takata Offers "sincerest Condolences" To Victims of Malfunctioning Airbag

Reuters - US Online Video (Nov. 20, 2014) — U.S. Congress hears from a victim and company officials as it holds a hearing on the safety of Takata airbags after reports of injuries. Rough Cut (no reporter narration). Video provided by Reuters
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
 
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:  

Breaking News:

Strange & Offbeat Stories

 

Space & Time

Matter & Energy

Computers & Math

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:  

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile iPhone Android Web
Follow Facebook Twitter Google+
Subscribe RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins