A New Breakthrough in Thermoelectric
Materials
April
2nd, 2015
A joint South Korean and American research
group has developed a scalable production method for a state of the art alloy
for the use in solid state thermoelectric devices. This new alloy is nearly twice as efficient
as existing materials and may lead to a new host of applications. Uses include refrigeration, consumer
electronics, transportation as well as novel devices which have not been
produced yet do to the inefficiencies of existing materials.
French physicist Jean Charles Athanase
Peltier discovered a key concept necessary for thermoelectric (TE) temperature
control in 1834. His findings were so
significant, TE devices are now commonly referred to Peltier devices. Since his work, there have been steady
advancements in materials and design.
Despite the technological sophistication Peltier devices, they are still
less energy efficient than traditional compressor/evaporation cooling.
In the 1960’s, Peltier devices were
primarily made from Bismuth-Telluride (Bi2Te3) or Antimony-Telluride (Sb2Te3)
alloys and had a peak efficiency (zT) of 1.1, meaning the electricity going in
was only slightly less than the heat coming out. Since the 1960’s there have been incremental
advancements in alloy technology used in Peltier devices.
In 2014, researchers in South Korea at IBS
Center for Integrated Nanostructure Physics along with Samsung Advanced
Institute of Technology, the Department of Nano Applied Engineering at Kangwon
National University, the Department of Energy Science at Sungkyunkwan
University, and Materials Science department at California Institute of
Technology California, USA have formulated a new method for creating a novel
and much more efficient TE alloy.
TE alloys are special because the metals
have an incredibly high melting point.
Instead of melting the metals to fuse them, they are combined through a
process called sintering which uses heat and/or pressure to join the small,
metallic granules. The joint team,
including IBS researchers, used a process called liquid-flow assisted sintering
which combined all three antimony, bismuth and telluride granules into one
alloy (Bi0.5Sb1.5Te3). Additional melted
tellurium was used as the liquid between the Bi0.5Sb1.5Te3 granules to help
fuse them into a solid alloy, and excess Te is expelled in the process.
By creating the alloy this way, the joints
between the fused grains, also known as the grain boundaries, took on a special
property. Traditionally sintered Bi0.5Sb1.5Te3 have thick, coarse joints which
have led to a decrease in both thermal and electrical conductivity. The new liquid-phase sintering creates grain
boundaries which are organized and aligned in seams called dislocation
arrays. These dislocation arrays greatly
reduce their thermal conduction, leading to an enhancement of their thermoelectric
conversion efficiency.
In tests, the efficiency (zT) reached 2.01
at 320 K within the range of 1.86 ±0.15 at 320 K (46.85° C) for 30 samples,
nearly doubling the industry standard.
When the melt spun Bi0.5Sb1.5Te3 alloy is used in a Peltier cooler, the
results are also significant. The new
material was able achieve a temperature change of 81 K at 300 K (26.85° C).
The applications for such a material are
abundant. As new fabrication techniques
are developed, Peltier cooling devices may be used in place of traditional
compression refrigeration systems. More
importantly, as electrical vehicles and personal electronic devices become more
ubiquitous in our daily lives, it is becoming increasingly necessary to have more
efficient systems for localized electrical power generation and effective
cooling mechanisms. This new
thermoelectric alloy paves the way for the future of modern TE devices.
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Notes for editors
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References Sang Il Kim, Kyu Hyoung Lee, Hyeon A. Mun,
Hyun Sik Kim, Sung Woo Hwang, Jong Wook Roh, Dae Jin Yang, Weon Ho Shin, Xiang
Shu Li, Young Hee Lee, G. Jeffrey
Snyder, Sung Wng Kim(2015). Dense dislocation arrays embedded in grain
boundaries for high-performance bulk thermoelectric. SCIENCE. DOI:10.1126/science.aaa4166
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For further information or to request media assistance, please contact:
Mr. Shi Bo Shim, Head of Department of Communications, IBS(+82-42-878-8189;
sibo@ibs.re.kr) or Ms. Sunny Kim, Department of Communications,
IBS(+82-42-878-8135; Sunnykim@ibs.re.kr)
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About Institute for Basic Science (IBS)
The IBS was founded in 2011 by the
government of the Republic of Korea. With the sole purpose of driving forward
the development of basic science in Korea, IBS will be comprised of a total of
50 research centers in all fields of basic science, including mathematics,
physics, chemistry, life science, earth science and interdisciplinary science.
IBS has launched 24 research centers as of January 2015. There is one
mathematics, eight physics, six chemistry, seven life science, and two
interdisciplinary research centers.
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