Thermoelectric response of carbon nanotube films to Au-nanoparticle incorporation

• Effects of incorporation of Au nanoparticles into CNT films.
• Addition of Au nanoparticles favorably changed some thermoelectric properties.
• Small nanoparticles lowered thermal conductivity, large nanoparticles increased it.
• Possible phonon scattering effect with small Au particles.

We report on a study of the effects on the thermoelectric properties of CNT films of incorporating Au nanoparticles of different sizes. Our characterization included measurements of the electrical conductivity, thermal conductivity, and Seebeck coefficient, as well as estimation of the power factor and dimensionless thermoelectric figure of merit for these materials. We found that the thermoelectric properties were significantly affected by the size of Au-nanoparticles used. Addition of Au-nanoparticles of both small (~5 nm) and large (~60 nm) diameters led to a decrease in the electrical conductivity from 1.8 × 105 Sm−1 for the pure CNT film to 6.2 × 104 and 7.9 × 104 Sm−1 for samples functionalized with 5 nm and 60 nm Au-NPs, respectively. Addition of 5 nm Au-nanoparticles also led to a decrease in the thermal conductivity to 73 Wm−1K−1 from 82 Wm−1K−1 for the pure CNT film, whereas the thermal conductivity of the sample with 60 nm Au-nanoparticles increased to 106 Wm−1K−1. The pure CNT film had a Seebeck coefficient of 31 μVK−1, while the samples with 5 and 60 nm Au-NPs only achieved ~25 μVK−1. The best value for the thermoelectric figure of merit (ZT) was 6.04 × 10−4 for the pure CNT film, and 1.73 × 10−4 and 1.33 × 10−4 for the samples with 5 nm and 60 nm Au-NPs. The power factors were found to be 1.67 × 10−4, 4.2 × 10−5, and 4.7 × 10−5 Wm−1K−2 for the pure CNT, and the samples with 5 and 60 nm Au-NPs, respectively.

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