Researchers report high thermoelectric powers in one-dimensional crystals for practical low-temperature cooling
- Source:
- Nagoya University
- Summary:
- Researchers studied the thermal and electrical properties of one-dimensional crystals composed of tantalum, silicon and tellurium for thermoelectric cooling at temperatures below 250 K (-23°C). The thermoelectric characteristics of these crystals were varied at temperatures ranging from the cryogenic level of 50 K up to room temperature by doping with molybdenum and antimony. The crystals' thermoelectric power factors greatly exceeded those of conventional materials around room temperature, indicating their suitability for low-temperature applications.
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Ta4SiTe4 whisker crystals (left
lower) show very large thermoelectric power?exceeding -400 ?V K-1 at low
temperature, while maintaining low electrical resistivity (right
upper). This results in that thermoelectric power factor (right lower),
an indication of cooling power, becomes a very large value far exceeding
those of the practical materials (typically 40 ?W cm-1 K-2 for the
Bi2Te3-based material). The optimum temperature of the power factor can
be widely controlled by molybdenum (Mo) or antimony (Sb) doping.
Credit: Yoshihiko Okamoto
Thermoelectric cooling is a solid-state
refrigeration process where the heat in an electrically conductive
material is transferred using the material's own conduction electrons
without any need for the gaseous coolants, such as chlorofluorocarbons,
that are used in conventional refrigeration. Coolers based on
thermoelectric technology can be scaled down in size without changing
their thermal-to-electrical energy conversion efficiency and this is a
major advantage for localized cooling of tiny electronic devices. This
effect is already used for temperature control in devices such as
infrared sensors and laser diodes, and has also been used to provide
low-temperature refrigeration for cryogenic electronic devices like
superconducting sensors.
However, the lack of materials with suitable thermoelectric
efficiency for practical cooling applications at temperatures below 250 K
(approximately -23°C) has driven researchers at Nagoya University to
look at the effectiveness of new compounds for truly low-temperature
applications.
"We studied the thermoelectric properties of whisker-like crystals composed of a compound of tantalum, silicon and tellurium," says corresponding author Yoshihiko Okamoto from Nagoya University's Department of Applied Physics. "These crystals produced very high thermoelectric powers over a wide temperature range, from the cryogenic level of 50 K (which is around -223°C) up to room temperature, but still maintained the low electrical resistivity that is needed for practical cooling applications." The samples that were grown for the experiments included pure Ta4SiTe4 and other crystals that were chemically doped with low levels of molybdenum and antimony.
Various material properties were measured for the samples, including thermoelectric power, electrical resistivity, and thermal conductivity, to compare the effects of the two dopants on their thermoelectric characteristics. "We measured a very high thermoelectric power factor at an optimum temperature of 130 K," adds Okamoto. "However, this optimum temperature could be controlled over a very broad range by varying the chemical doping, and indicates that these crystals are suitable for practical low-temperature use."
Addition of as little as 0.1% molybdenum doping caused the resistivity of the telluride-type crystals to decrease dramatically at low temperatures, while they also demonstrated high thermoelectric powers that were closely related to the strongly one-dimensional electronic structures of the materials. The power factors of the crystals at room temperature greatly exceeded the corresponding values of the conventional Bi2Te3-based alloys that are commonly used in thermoelectric applications, and these crystals thus represent a highly promising route towards the development of high-performance thermoelectric cooling solutions at very low temperatures.
"We studied the thermoelectric properties of whisker-like crystals composed of a compound of tantalum, silicon and tellurium," says corresponding author Yoshihiko Okamoto from Nagoya University's Department of Applied Physics. "These crystals produced very high thermoelectric powers over a wide temperature range, from the cryogenic level of 50 K (which is around -223°C) up to room temperature, but still maintained the low electrical resistivity that is needed for practical cooling applications." The samples that were grown for the experiments included pure Ta4SiTe4 and other crystals that were chemically doped with low levels of molybdenum and antimony.
Various material properties were measured for the samples, including thermoelectric power, electrical resistivity, and thermal conductivity, to compare the effects of the two dopants on their thermoelectric characteristics. "We measured a very high thermoelectric power factor at an optimum temperature of 130 K," adds Okamoto. "However, this optimum temperature could be controlled over a very broad range by varying the chemical doping, and indicates that these crystals are suitable for practical low-temperature use."
Addition of as little as 0.1% molybdenum doping caused the resistivity of the telluride-type crystals to decrease dramatically at low temperatures, while they also demonstrated high thermoelectric powers that were closely related to the strongly one-dimensional electronic structures of the materials. The power factors of the crystals at room temperature greatly exceeded the corresponding values of the conventional Bi2Te3-based alloys that are commonly used in thermoelectric applications, and these crystals thus represent a highly promising route towards the development of high-performance thermoelectric cooling solutions at very low temperatures.
Story Source:
Materials provided by Nagoya University. Note: Content may be edited for style and length.
Materials provided by Nagoya University. Note: Content may be edited for style and length.
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