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Thermoelectric materials could play a crucial role in the future of wearable electronic devices. They can continuously generate electricity from body heat. For efficient operation in wearable systems, in addition to a high thermoelectric figure of merit, zT, the thermoelectric material must have low thermal conductivity and a high Seebeck coefficient. In this study, we successfully synthesized high-performance nanocomposites of n-type Bi2Te2.7Se0.3, optimized especially for body heat harvesting and power generation applications. Different techniques such as dopant optimization, glass inclusion, microwave radiation in a single mode microwave cavity, and sintering conditions were used to optimize the temperature-dependent thermoelectric properties of Bi2Te2.7Se0.3. The effects of these techniques were studied and compared with each other. A room temperature thermal conductivity as low as 0.65 W/mK and high Seebeck coefficient of −297 μV/K were obtained for a wearable application, while maintaining a high thermoelectric figure of merit, zT, of 0.87 and an average zT of 0.82 over the entire temperature range of 25 °C to 225 °C, which makes the material appropriate for a variety of power generation applications.
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Development of Nanocomposite Thermoelectric Generators for Body Heat Harvesting
This work evaluates wearable thermoelectric (TE) devices consisting of nanocomposite thermoelectric materials, aluminum nitride ceramic headers, and a flexible and stretchable circuit board. These types of wearable systems are part of a broader effort to harvest thermal energy from the body and convert it into electrical energy to power wearable electronics. Thermoelectric generators are made of p-type (Bi,Sb)2Te3 and n-type Bi2(Te,Se)3. The nanocomposite thermoelectric materials investigated in this research address the two fundamental challenges for body heat harvesting. The first challenge is related to the unavailability of high zT n-type materials near the body temperature. The second challenge is related to the thermoelectric power factor. To improve the zT, one has to increase the power factor simultaneously while reducing the thermal conductivity. Our nanocomposites result in enhancement of the TE power factor along with the reduction of the thermal conductivity. The fundamental reason is a nanoscale effect that happens only when the energy distribution function of the carriers does not relax to that of the bulk material in the crystallites. Ten p-type and ten n-type nanocomposite ingots were synthesized and characterized in this research. All ingots were characterized versus their thermoelectric properties and they all showed similarly enhanced properties. Our nanocomposites, compared to commercial materials, have better zT and thermal resistivity by 40% and 75% for p-type, respectively, and 15% and 140% for n-type. Compared to the state-of-the-art materials, our nanocomposites produce significantly higher power due to their optimized properties for the body temperature.
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- Award ID(s):
- 1711253
- PAR ID:
- 10106239
- Date Published:
- Journal Name:
- Undergraduate Research Symposium
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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