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 Mat4Rail: EU Research Project on the Railway of the Future
23.02.2018 | Universität Bremen

nachricht Atomic structure of ultrasound material not what anyone expected
21.02.2018 | North Carolina State University

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Attoseconds break into atomic interior

A newly developed laser technology has enabled physicists in the Laboratory for Attosecond Physics (jointly run by LMU Munich and the Max Planck Institute of Quantum Optics) to generate attosecond bursts of high-energy photons of unprecedented intensity. This has made it possible to observe the interaction of multiple photons in a single such pulse with electrons in the inner orbital shell of an atom.

In order to observe the ultrafast electron motion in the inner shells of atoms with short light pulses, the pulses must not only be ultrashort, but very...

Im Focus: Good vibrations feel the force

A group of researchers led by Andrea Cavalleri at the Max Planck Institute for Structure and Dynamics of Matter (MPSD) in Hamburg has demonstrated a new method enabling precise measurements of the interatomic forces that hold crystalline solids together. The paper Probing the Interatomic Potential of Solids by Strong-Field Nonlinear Phononics, published online in Nature, explains how a terahertz-frequency laser pulse can drive very large deformations of the crystal.

By measuring the highly unusual atomic trajectories under extreme electromagnetic transients, the MPSD group could reconstruct how rigid the atomic bonds are...

Im Focus: Developing reliable quantum computers

International research team makes important step on the path to solving certification problems

Quantum computers may one day solve algorithmic problems which even the biggest supercomputers today can’t manage. But how do you test a quantum computer to...

Im Focus: In best circles: First integrated circuit from self-assembled polymer

For the first time, a team of researchers at the Max-Planck Institute (MPI) for Polymer Research in Mainz, Germany, has succeeded in making an integrated circuit (IC) from just a monolayer of a semiconducting polymer via a bottom-up, self-assembly approach.

In the self-assembly process, the semiconducting polymer arranges itself into an ordered monolayer in a transistor. The transistors are binary switches used...

Im Focus: Demonstration of a single molecule piezoelectric effect

Breakthrough provides a new concept of the design of molecular motors, sensors and electricity generators at nanoscale

Researchers from the Institute of Organic Chemistry and Biochemistry of the CAS (IOCB Prague), Institute of Physics of the CAS (IP CAS) and Palacký University...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

2nd International Conference on High Temperature Shape Memory Alloys (HTSMAs)

15.02.2018 | Event News

Aachen DC Grid Summit 2018

13.02.2018 | Event News

How Global Climate Policy Can Learn from the Energy Transition

12.02.2018 | Event News

 
Latest News

Basque researchers turn light upside down

23.02.2018 | Physics and Astronomy

Finnish research group discovers a new immune system regulator

23.02.2018 | Health and Medicine

Attoseconds break into atomic interior

23.02.2018 | Physics and Astronomy

VideoLinks
Science & Research
Overview of more VideoLinks >>>