Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Surprising material could play role in saving energy

17.04.2014

Researchers discover tin selenide is best at converting waste heat to electricity

One strategy for addressing the world's energy crisis is to stop wasting so much energy when producing and using it, which can happen in coal-fired power plants or transportation. Nearly two-thirds of energy input is lost as waste heat.

Now Northwestern University scientists have discovered a surprising material that is the best in the world at converting waste heat to useful electricity. This outstanding property could be exploited in solid-state thermoelectric devices in a variety of industries, with potentially enormous energy savings.

An interdisciplinary team led by inorganic chemist Mercouri G. Kanatzidis found the crystal form of the chemical compound tin selenide conducts heat so poorly through its lattice structure that it is the most efficient thermoelectric material known. Unlike most thermoelectric materials, tin selenide has a simple structure, much like that of an accordion, which provides the key to its exceptional properties.

The efficiency of waste heat conversion in thermoelectrics is reflected by its figure of merit, called ZT. Tin selenide exhibits a ZT of 2.6, the highest reported to date at around 650 degrees Celsius. The material's extremely low thermal conductivity boosts the ZT to this high level, while still retaining good electrical conductivity.

The ZT metric represents a ratio of electrical conductivity and thermoelectric power in the numerator (which needs to be high) and thermal conductivity in the denominator (which needs to be low).

Potential areas of application for the high-temperature thermoelectric material include the automobile industry (a significant amount of gasoline's potential energy goes out of a vehicle's tailpipe), heavy manufacturing industries (such as glass and brick making, refineries, coal- and gas-fired power plants) and places where large combustion engines operate continuously (such as in large ships and tankers).

"A good thermoelectric material is a business proposition -- as much commercial as it is scientific," said Vinayak P. Dravid, a senior researcher on the team. "You don't have to convert much of the world's wasted energy into useful energy to make a material very exciting. We need a portfolio of solutions to the energy problem, and thermoelectric materials can play an important role."

Dravid is the Abraham Harris Professor of Materials Science and Engineering at the McCormick School of Engineering and Applied Science.

Details of tin selenide, probably among the world's least thermally conductive crystalline materials, are published today (April 17) by the journal Nature.

The discovery comes less than two years after the same research group broke the world record with another thermoelectric material they developed in the lab with a ZT of 2.2.

"The inefficiency of current thermoelectric materials has limited their commercial use," said Kanatzidis, the Charles E. and Emma H. Morrison Professor of Chemistry in the Weinberg College of Arts and Sciences. "We expect a tin selenide system implemented in thermoelectric devices to be more efficient than other systems in converting waste heat to useful electricity."

The material, despite having a very simple structure, conducts heat so poorly that even moderate thermoelectric power and electrical conductivity are enough to provide high thermoelectric performance at high temperature.

The researchers did not expect to find tin selenide to be such a good thermoelectric material.

"Lidong Zhao, the first author of the paper, deserves a lot of credit for looking at tin selenide," said Kanatzidis, who also holds a joint appointment at Argonne National Laboratory. "He is a good example of the curious people we try to attract to Northwestern."

Zhao, a postdoctoral fellow in Kanatzidis' research group, grew crystals of tin selenide and measured the crystal in three directions, along each axis. He found that the thermal conductivity was "ridiculously low" along the a-axis but also along the other two axes.

"The results are eye-opening because they point in a direction others would not look," Dravid said. "This material has the potential to be applied to other areas, such as thermal barrier coatings."

Kanatzidis and Zhao identified the potential of the material intuitively by looking at its crystal structure. They confirmed its exceptional thermoelectric properties and then turned to Dravid and Christopher M. Wolverton to uncover how the crystal was behaving and why.

"We found that the bonds between some atoms in this compound are very weak and lead to exceptionally soft, floppy atomic vibrations," said Wolverton, a senior author of the paper and a professor of materials science at the McCormick School.

Wolverton, an expert in computational materials science related to energy applications, showed that the accordion-like structure and weak bonds lead to atoms that vibrate very slowly.

"These very weak vibrations are responsible for the inability of the material to conduct heat," Wolverton said. "Our theory provides the scientific basis as to why the material behaves the way it does and also provides us with a new direction to search for even higher-efficiency materials."

"Tin selenide reminds us of that popular TV commercial for a memory foam mattress in which a person can jump on one side of the mattress while a glass of wine a few feet away is unperturbed -- the vibrations do not reach the glass because of the mattress' material," Kanatzidis said.

"Similarly, in tin selenide, heat cannot travel well through this material because its soft, accordion-like structure doesn't transmit vibrations well," he said. "One side of tin selenide gets hot -- where the waste heat is, for example -- while the other side remains cool. This enables the hot side to generate useful electricity."

"Our discovery underscores why the Department of Energy EFRC program works," Kanatzidis said. "A multidisciplinary team, such as ours, can look at a problem from many different angles, with sustained funding increasing the chances of a scientific breakthrough. And we have a special ambience here -- the spirit of Northwestern is interdisciplinary."

###

The paper is titled "Ultralow thermal conductivity and high thermoelectric figure of merit in SnSe crystals." In addition to Kanatzidis, Dravid, Wolverton and Zhou, other authors of the paper are Yongsheng Zhang and Gangjian Tan, of Northwestern, and Hui Sun and Ctirad Uher, of the University of Michigan.

Megan Fellman | Eurek Alert!
Further information:
http://www.northwestern.edu

Further reports about: conductivity electricity found glass heat large play structure vibrations

More articles from Materials Sciences:

nachricht Move over, Superman! NIST method sees through concrete to detect early-stage corrosion
27.04.2017 | National Institute of Standards and Technology (NIST)

nachricht Control of molecular motion by metal-plated 3-D printed plastic pieces
27.04.2017 | Ecole Polytechnique Fédérale de Lausanne

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Making lightweight construction suitable for series production

More and more automobile companies are focusing on body parts made of carbon fiber reinforced plastics (CFRP). However, manufacturing and repair costs must be further reduced in order to make CFRP more economical in use. Together with the Volkswagen AG and five other partners in the project HolQueSt 3D, the Laser Zentrum Hannover e.V. (LZH) has developed laser processes for the automatic trimming, drilling and repair of three-dimensional components.

Automated manufacturing processes are the basis for ultimately establishing the series production of CFRP components. In the project HolQueSt 3D, the LZH has...

Im Focus: Wonder material? Novel nanotube structure strengthens thin films for flexible electronics

Reflecting the structure of composites found in nature and the ancient world, researchers at the University of Illinois at Urbana-Champaign have synthesized thin carbon nanotube (CNT) textiles that exhibit both high electrical conductivity and a level of toughness that is about fifty times higher than copper films, currently used in electronics.

"The structural robustness of thin metal films has significant importance for the reliable operation of smart skin and flexible electronics including...

Im Focus: Deep inside Galaxy M87

The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.

Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...

Im Focus: A Quantum Low Pass for Photons

Physicists in Garching observe novel quantum effect that limits the number of emitted photons.

The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...

Im Focus: Microprocessors based on a layer of just three atoms

Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.

Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Fighting drug resistant tuberculosis – InfectoGnostics meets MYCO-NET² partners in Peru

28.04.2017 | Event News

Expert meeting “Health Business Connect” will connect international medical technology companies

20.04.2017 | Event News

Wenn der Computer das Gehirn austrickst

18.04.2017 | Event News

 
Latest News

Wireless power can drive tiny electronic devices in the GI tract

28.04.2017 | Medical Engineering

Ice cave in Transylvania yields window into region's past

28.04.2017 | Earth Sciences

Nose2Brain – Better Therapy for Multiple Sclerosis

28.04.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>