Materials Science and Engineering

Biography

Biography: Chia-Jyi Liu

Abstract

Thermoelectric materials can be used to generate electricity from waste heat via the Seebeck effect. High-energy input is often required to fabricate thermoelectric materials. In this talk, we present  a green route to synthesize Ag₂Te-Ag nanocomposites with the reaction taking place in one pot at room temperature without any organic substance involved. Various amounts of silver in the Ag₂Te-Ag nanocomposite can be obtained depending on the reaction period of time. A possible mechanism is presented for the formaiton of Ag₂Te-Ag nanocomposite. A core-shell structure at the incipient stage of Ag₂Te growth can be observed. However, the reaction duriation has a significant effect on the electrical transport behavior of the nanocomposites due to presence of various amounts of Ag, which might be beneficial for enhancing the performance of thermoelectric composites.

We also present a rapid route for fabricating co-doped Co_1-x-yNi_xFe_ySb₃ using hydrothermal methods. Hydrothermal synthesis was carried out at 170^°C for a duration of 12 h, followed by evacuated-and-encapsulated heating at 580^°C for a short period of 5 h. The resulting samples are characterized using powder x-ray diffraction, density, electronic and thermal transport measurements. Due to the bipolar effects on thermopower are shifted to higher temperatures as compared with the nondoped CoSb₃, the power factor of Co_1-x-yNi_xFe_ySb₃ is significantly enhanced in the high temperature region due to significant enhancement of the electrical conductivity and absolute value of thermopower. The thermal conductivity of Co_0.76Ni_0.14Fe_0.10Sb₃ decreases with temperature down to 1.02 Wm^-1K^-1 at 600 K. As a result, the largest zT of 0.68 is attained for Co_0.76Ni_0.14Fe_0.10Sb₃ at 600 K. We also analyze the lattice thermal conductivity to gain insight into the contribution of various scattering processes that suppress the heat transfer through the phonons in Co_1-x-yNi_xFe_ySb₃.