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 Lowering the Heat Makes New Materials Possible While Saving Energy
26.09.2016 | Penn State Materials Research Institute

nachricht Scientists Find Twisting 3-D Raceway for Electrons in Nanoscale Crystal Slices
26.09.2016 | Lawrence Berkeley National Laboratory

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: First quantum photonic circuit with electrically driven light source

Optical quantum computers can revolutionize computer technology. A team of researchers led by scientists from Münster University and KIT now succeeded in putting a quantum optical experimental set-up onto a chip. In doing so, they have met one of the requirements for making it possible to use photonic circuits for optical quantum computers.

Optical quantum computers are what people are pinning their hopes on for tomorrow’s computer technology – whether for tap-proof data encryption, ultrafast...

Im Focus: OLED microdisplays in data glasses for improved human-machine interaction

The Fraunhofer Institute for Organic Electronics, Electron Beam and Plasma Technology FEP has been developing various applications for OLED microdisplays based on organic semiconductors. By integrating the capabilities of an image sensor directly into the microdisplay, eye movements can be recorded by the smart glasses and utilized for guidance and control functions, as one example. The new design will be debuted at Augmented World Expo Europe (AWE) in Berlin at Booth B25, October 18th – 19th.

“Augmented-reality” and “wearables” have become terms we encounter almost daily. Both can make daily life a little simpler and provide valuable assistance for...

Im Focus: Artificial Intelligence Helps in the Discovery of New Materials

With the help of artificial intelligence, chemists from the University of Basel in Switzerland have computed the characteristics of about two million crystals made up of four chemical elements. The researchers were able to identify 90 previously unknown thermodynamically stable crystals that can be regarded as new materials. They report on their findings in the scientific journal Physical Review Letters.

Elpasolite is a glassy, transparent, shiny and soft mineral with a cubic crystal structure. First discovered in El Paso County (Colorado, USA), it can also be...

Im Focus: Complex hardmetal tools out of the 3D printer

For the first time, Fraunhofer IKTS shows additively manufactured hardmetal tools at WorldPM 2016 in Hamburg. Mechanical, chemical as well as a high heat resistance and extreme hardness are required from tools that are used in mechanical and automotive engineering or in plastics and building materials industry. Researchers at the Fraunhofer Institute for Ceramic Technologies and Systems IKTS in Dresden managed the production of complex hardmetal tools via 3D printing in a quality that are in no way inferior to conventionally produced high-performance tools.

Fraunhofer IKTS counts decades of proven expertise in the development of hardmetals. To date, reliable cutting, drilling, pressing and stamping tools made of...

Im Focus: Launch of New Industry Working Group for Process Control in Laser Material Processing

At AKL’16, the International Laser Technology Congress held in May this year, interest in the topic of process control was greater than expected. Appropriately, the event was also used to launch the Industry Working Group for Process Control in Laser Material Processing. The group provides a forum for representatives from industry and research to initiate pre-competitive projects and discuss issues such as standards, potential cost savings and feasibility.

In the age of industry 4.0, laser technology is firmly established within manufacturing. A wide variety of laser techniques – from USP ablation and additive...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

European Health Forum Gastein 2016 kicks off today

28.09.2016 | Event News

Laser use for neurosurgery and biofabrication - LaserForum 2016 focuses on medical technology

27.09.2016 | Event News

Experts from industry and academia discuss the future mobile telecommunications standard 5G

23.09.2016 | Event News

 
Latest News

European Health Forum Gastein 2016 kicks off today

28.09.2016 | Event News

New switch decides between genome repair and death of cells

27.09.2016 | Life Sciences

Nanotechnology for energy materials: Electrodes like leaf veins

27.09.2016 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>