Abstract
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.
Highlights
One of the most promising technologies for waste heat recovery from environmental sources is based on thermoelectric generators in which the temperature gradient is directly converted to electricity.The conversion efficiency of the thermoelectric materials depends on the thermoelectric dimensionless figure of merit, zT, i.e.: S2 σ zT = T (1)κ where S is the Seebeck coefficient in μV/K, σ is the electrical conductivity in S/cm, κ is the thermal conductivity inW/mK, and T is the absolute temperature in K [1]
We investigated the effect of several parameters, including dopant addition, tellurium vacancies, glass inclusion, sintering time and temperature, microwave processing, and subsequent annealing, primarily to fully optimize the thermoelectric properties of bulk nanostructured n-type Bi2 Te2.7 Se0.3 materials
We synthesized high-performance nanocomposites of n-type Bi2 Te2.7 Se0.3 for body heat harvesting
Summary
One of the most promising technologies for waste heat recovery from environmental sources is based on thermoelectric generators in which the temperature gradient is directly converted to electricity. A larger output voltage at the device level is required to run the boost converter and the power management unit efficiently This is fulfilled through materials with high Seebeck coefficients. There are a few studies that have shown high zT values for n-type Bi2 Te3 , these materials are not appropriate for applications such as body heat harvesting due to their non-optimized properties at body temperature. For body heat harvesting applications, thermoelectric materials require a combination of high zT, low κ, and high S at room temperature [23]. For applications at above 100 ◦ C (i.e., power generation), low κ is not determinative; high S and zT are still demanded To fulfill these requirements, we synthesized optimized nanostructured n-type materials based on Bi2 Te2.7 Se0.3. Materials with excellent properties at room temperature are desired for wearable applications, while those with good features at above 150 ◦ C are useful for high-temperature power generation
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