Thermal Conductivity Measurements of Aggregated (Bi1-x Sb x )2Te3 Nanoparticles Using 3ω Method

Using the 3 omega method based on the two heat flow model, the thermal conductivity of as-dried and thermally treated samples of (Bi1-x Sb (x) )(2)Te-3 inks in the form of aggregated nanoparticles was measured. For the as-dried sample, kappa (sample) was 0.2 W K-1 m(-1) to 0.3 W K-1 m(-1). That of the thermally treated sample was 0.4 W K-1 m(-1) to 0.7 W K-1 m(-1). Organic solvent remained in the as-dried sample, covering the (Bi1-x Sb (x) )(2)Te-3 nanoparticles. In the region where organic solvent remained between the nanoparticles, heat flow was impeded because the thermal conductivity of the organic solvent is lower than that of the (Bi1-x Sb (x) )(2)Te-3 nanoparticles. However, in the thermally treated sample, the organic solvent evaporated and the nanoparticles grew due to the effects of the thermal treatment process. In this case, factors impeding heat flow, such as the interfacial thermal resistance between the particles, were limited. Therefore, this difference in kappa (sample), which is consistent with the grain growth as ascertained from powder x-ray diffraction measurements, can be attributed to the evaporation of the organic solvent.