Researchers at Tokyo University of Science have demonstrated a novel way of converting heat into electricity using the semimetal tungsten disilicide. This new way could lead to more efficient thermoelectric devices, achieving efficient conversion without significant loss.
As thermoelectric materials convert heat into electricity, they have emerged as valuable tools for harvesting waste heat. These materials are crucial in industries and vehicles, where the waste heat is used to furnish additional power. More importantly, thermoelectric materials also reach areas where power sources are impracticable.
Traditional thermoelectric devices generate voltage in the same direction of heat flow. These devices are called parallel thermoelectric devices that use two types of parallel material, p-type and n-type, to generate electricity in opposite directions. This property is called axis-dependent conduction polarity (ADCP).
These devices are often connected in series to produce a higher voltage. However, this leads to more touchpoints, increasing electrical resistance and, thereby, power loss.
Contrary to these conventional thermoelectric devices, transverse thermoelectric devices allow energy generation in the perpendicular direction of the heat flow. These devices have fewer contact points, enabling efficient electrical energy conversion.
Materials that conduct positive charges (p-type) in one direction and negative charges (n-type) in another are suitable candidates for such transverse thermoelectric devices. However, the direct presentation of transverse thermoelectric devices was poorly studied.
Researchers achieved the transverse thermoelectric effect (TTE) in the semimetal tungsten silicide (WSi2), bringing about a breakthrough in clean energy.
“Transverse thermoelectric conversion is a phenomenon that is gaining attention as a new core technology for sensors capable of measuring temperature and heat flow. However, there are only a limited number of such materials, and no design guidelines have been established. This is the first direct demonstration of the transverse thermoelectric conversion in WSi2,” says Ryuji Okazaki.
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Researchers utilized physical experiments and computer simulations to analyze the properties of WSi2. The team studied the thermopower, electrical resistivity, and thermal conductivity of a WSi2 crystal along its two crystallographic axes at low temperatures. They discovered the unique electronic structure grants ADCP. WSi2’s structure creates direction-specific conductivity, enabling the TTE effect.
The lead author, Ryuji Okazaki, and colleagues demonstrated a voltage perpendicular to the temperature difference via direct TTE generation.
“Our results indicate that WSi2 is a promising candidate for TTE-based devices. We hope this research will lead to the development of new sensors and the discovery of new transverse thermoelectric materials,” says Prof. Okazaki.
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Journal Reference
- Shoya Ohsumi, Yoshiki J. Sato, and Ryuji Okazaki. Transverse Thermoelectric Conversion in the Mixed-Dimensional Semimetal WSi2. PRX Energy. DOI: 10.1103/PRXEnergy.3.043007
