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Researchers are developing layered cobalt oxide with a record thermoelectric figure of merit

Barium-cobalt oxide film (upper right, about 1 cm2) exposed to an open flame to generate voltage.Credit: Hiromichi Ota

Waste heat is a very promising renewable energy source. However, the efficiency of using heat to generate energy has historically been much lower than that of hydro, wind and solar. There are many materials that can be used to generate energy from waste heat, but they all suffer from problems ranging from instability to inefficiency. Nevertheless, the fact that many industries generate large amounts of waste heat has driven research in this area.


A team of scientists led by Professor Hiromichi Ota of the Institute of Electronic Science (RIES), Hokkaido University has recently developed layered cobalt oxide with record thermoelectric performance of metal oxides at room temperature.Their findings were published in the journal Journal of Materials Chemistry A..

The thermoelectric conversion is driven by the Seebeck effect. If there is a temperature difference between the ends of the conductive material, an electric current will be generated. Historically, the efficiency of heat-to-electricity conversion of metal oxides has been very low. However, metal oxide-based thermoelectric devices are highly desired because of their environmental compatibility. The thermoelectric conversion efficiency of a device depends on an important factor called the thermoelectric figure of merit (ZT).

Hiromichi Ota’s group has developed a layered cobalt oxide that exhibits high ZT and is stable at various operating temperatures. The famous sodium-cobalt oxide, which alternates layers of sodium and cobalt oxide, shows a very low ZT of about 0.03, while the material developed by the Ota group achieved a ZT of 0.11. .. This group replaced sodium with other alkali metals or alkaline earth metals (calcium, strontium, barium).

研究者は、記録的な熱電性能指数を備えた層状酸化コバルトを開発しています

Hypothesis of ZT improvement of layered cobalt oxide. Ions with a large atomic weight (right) suppress the thermal conductivity of the cobalt oxide layer, resulting in an increase in ZT. Credit: Yugo Takashima and others, Journal of Materials Chemistry A, October 13, 2020

The layered barium-cobalt oxide material showed a record ZT of 0.11 at room temperature. The increase in ZT is directly caused by the decrease in thermal conductivity of barium. As scientists hypothesized, the higher the atomic weight, the lower the thermal conductivity, resulting in a higher ZT. This is because heavy atoms suppress the vibration of the cobalt oxide layer due to heating. Further research is needed to optimize the composition of the material for higher efficacy and stability and determine the most useful practical applications.

研究者は、記録的な熱電性能指数を備えた層状酸化コバルトを開発しています

Correlation between atomic weight and thermoelectric figure of merit (ZT). As the atomic weight of alkaline or alkaline earth metals increases, so does ZT. Orange, calcium; yellow, sodium; purple, strontium; green, barium. Credit: Yugo Takashima and others, Journal of Materials Chemistry A, October 13, 2020

Hiromichi Ota is the director of the Functional Thin Film Materials Laboratory at RIES, Hokkaido University. His areas of research include thermoelectricity, thermoelectric modulation, optoelectronics, and iontronics.


Efficiently convert heat into electricity by tampering with nanostructures


For more information:
Yugo Takashima et al. Layered cobalt oxide epitaxial film showing thermoelectric ZT = 0.11 at room temperature, Journal of Materials Chemistry A (2020). DOI: 10.1039 / d0ta07565e

Provided by Hokkaido University

Quote: Researchers have recorded a record thermoelectric performance index (12 2020) obtained on December 23, 2020 from https: //phys.org/news/2020-12-layered-cobalt-oxide-record-setting- We are developing layered cobalt oxide with (23rd of March) thermoelectric.html

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Researchers are developing layered cobalt oxide with a record thermoelectric figure of merit

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