Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Defects can 'Hulk-up' materials

21.05.2015

Berkeley lab study shows properly managed damage can boost material thermoelectric performances

In the story of the Marvel Universe superhero known as the Hulk, exposure to gamma radiation transforms scientist Bruce Banner into a far more powerful version of himself. In a study at Berkeley Lab, exposure to alpha-particle radiation has been shown to transform certain thermoelectric materials into far more powerful versions of themselves.


Cross sectional HRTEM image of bismuth telluride thin-film grown on gallium arsenide substrate.

Courtesy of Junqiao Wu, Berkeley Lab

"We've demonstrated that by irradiating a thermoelectric semiconductor with high-energy alpha particles, we can control native defects in the crystal so that these defects actually enhance the performance of the thermoelectric material by a factor of up to ten," says Junqiao Wu, a physicist who holds joint appointments with Berkeley Lab's Materials Sciences Division and the University of California Berkeley's Department of Materials Science and Engineering. "Although this discovery goes against common wisdom, it turns out that when properly managed, a damaged thermoelectric material is a better thermoelectric material."

The ability of thermoelectric materials to convert heat into electricity, or electricity into cooling, represents a potentially huge source of clean, green energy. Consequently, thermoelectric materials have been heavily investigated over the past several decades. Past studies have shown that the efficiency of heat-to-electricity conversion -- a metric known as the "figure-of-merit" or ZT -- is inherently limited by the coupling of three key parameters: electrical conductivity, thermopower and thermal conductivity.

"Usually thermopower is enhanced at the cost of a reduction in electrical conductivity," Wu says, "but we have been able to break this undesired coupling and demonstrate simultaneous increases in electrical conductivity of up to 200-percent, and thermopower of up to 70-percent."

By irradiating with alpha-particles thin-films of bismuth telluride, a well-characterized thermoelectric, Wu and his collaborators achieved a ZT value as high as 1.24, the highest rating ever recorded for bismuth telluride at room temperature.

"The alpha particles knocked out atoms from their lattice sites and introduced native defects such as vacancies and interstitials," says Joonki Suh, a member of Wu's research group and lead author of a paper describing this study (see below). "Normally, you would expect defects to degrade a material's performance, but the alpha particles inflicted relatively heavy damage beneath the surfaces of the bismuth telluride thin-films while allowing the surfaces to retain good electrical conductivity. The results were controlled native defects that acted beneficially and multi-functionally as electron donors and electron energy filters."

As they expect native defects to be generated and behave in a similar manner to what was accomplished with bismuth telluride across a wide range of narrow-bandgap semiconductors, Wu and his collaborators believe their technique can be used to improve the ZT values of other thermoelectric materials without the need for complicated and expensive materials processing.

"For example," Wu says, "one could use irradiation to improve the performance of thin-film thermoelectric devices that are potentially important for on-chip cooling of high-power electronics. One could also control the growth process of bulk thermoelectric materials to stabilize useful native defects."

In addition, thermoelectric materials are being groomed for use in radiative environments, such as outer space. The data provided by this study should provide helpful guidelines for the selection of future materials.

"From a fundamental science point of view, defects, especially native defects, have always been a focus of research in the materials sciences, but their role in coupled thermal-electrical transport, as well as in entropy-transporting in thermoelectric materials, has been poorly understood," Wu says. "Our work lays a solid foundation for a complete understanding of the physics behind these processes. It also serves as a reminder that defects in materials are not necessarily bad."

###

A paper describing this research has been published in the journal Advanced Materials. The paper is titled "Simultaneous Enhancement of Electrical Conductivity and Thermopower of Bi2Te3 by Multi-Functionality of Native Defects." Wu is the corresponding author, Suh is the lead author. Other authors are Kin Man Yu, Deyi Fu, Xinyu Liu, Fan Yang, Jin Fan, David Smith, Yong-Hang Zhang, Jacek Furdyna, Chris Dames and Wladyslaw Walukiewicz.

This research was primarily funded by the DOE Office of Science and the National Science Foundation.

Media Contact

Lynn Yarris
lcyarris@lbl.gov
510-486-5375

 @BerkeleyLab

http://www.lbl.gov 

Lynn Yarris | EurekAlert!

More articles from Materials Sciences:

nachricht Beyond conventional solution-process for 2-D heterostructure
22.06.2018 | Science China Press

nachricht Graphene assembled film shows higher thermal conductivity than graphite film
22.06.2018 | Chalmers University of Technology

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Temperature-controlled fiber-optic light source with liquid core

In a recent publication in the renowned journal Optica, scientists of Leibniz-Institute of Photonic Technology (Leibniz IPHT) in Jena showed that they can accurately control the optical properties of liquid-core fiber lasers and therefore their spectral band width by temperature and pressure tuning.

Already last year, the researchers provided experimental proof of a new dynamic of hybrid solitons– temporally and spectrally stationary light waves resulting...

Im Focus: Overdosing on Calcium

Nano crystals impact stem cell fate during bone formation

Scientists from the University of Freiburg and the University of Basel identified a master regulator for bone regeneration. Prasad Shastri, Professor of...

Im Focus: AchemAsia 2019 will take place in Shanghai

Moving into its fourth decade, AchemAsia is setting out for new horizons: The International Expo and Innovation Forum for Sustainable Chemical Production will take place from 21-23 May 2019 in Shanghai, China. With an updated event profile, the eleventh edition focusses on topics that are especially relevant for the Chinese process industry, putting a strong emphasis on sustainability and innovation.

Founded in 1989 as a spin-off of ACHEMA to cater to the needs of China’s then developing industry, AchemAsia has since grown into a platform where the latest...

Im Focus: First real-time test of Li-Fi utilization for the industrial Internet of Things

The BMBF-funded OWICELLS project was successfully completed with a final presentation at the BMW plant in Munich. The presentation demonstrated a Li-Fi communication with a mobile robot, while the robot carried out usual production processes (welding, moving and testing parts) in a 5x5m² production cell. The robust, optical wireless transmission is based on spatial diversity; in other words, data is sent and received simultaneously by several LEDs and several photodiodes. The system can transmit data at more than 100 Mbit/s and five milliseconds latency.

Modern production technologies in the automobile industry must become more flexible in order to fulfil individual customer requirements.

Im Focus: Sharp images with flexible fibers

An international team of scientists has discovered a new way to transfer image information through multimodal fibers with almost no distortion - even if the fiber is bent. The results of the study, to which scientist from the Leibniz-Institute of Photonic Technology Jena (Leibniz IPHT) contributed, were published on 6thJune in the highly-cited journal Physical Review Letters.

Endoscopes allow doctors to see into a patient’s body like through a keyhole. Typically, the images are transmitted via a bundle of several hundreds of optical...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Munich conference on asteroid detection, tracking and defense

13.06.2018 | Event News

2nd International Baltic Earth Conference in Denmark: “The Baltic Sea region in Transition”

08.06.2018 | Event News

ISEKI_Food 2018: Conference with Holistic View of Food Production

05.06.2018 | Event News

 
Latest News

Graphene assembled film shows higher thermal conductivity than graphite film

22.06.2018 | Materials Sciences

Fast rising bedrock below West Antarctica reveals an extremely fluid Earth mantle

22.06.2018 | Earth Sciences

Zebrafish's near 360 degree UV-vision knocks stripes off Google Street View

22.06.2018 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>