CuMSe for thermoelectric applications

• Main Author: Asgarali, Quresh
• Other Authors: Alex Yan Qingyu
• Format: Final Year Project
• Language: English
• Published: Nanyang Technological University 2020
• Subjects: Engineering::Materials::Microelectronics and semiconductor materials
• Online Access: https://hdl.handle.net/10356/137222
• Institution: Nanyang Technological University

Although demand for thermoelectrics may have shown promising advantages due to nanoscale features, thermoelectric materials have paid considerable attention to their ability to convert waste heat to useful electricity. A rebirth in thermoelectric study led to substantial improvements in the thermoelectric merit figure, zT, including materials that had previously been meticulously examined. This study focuses on thermoelectric zT optimization by developing a comprehensive analysis of the electronic structure through amalgamation of optical properties, ab initio computed electronic band structures and electronic / thermoelectric properties. In IV-VI semiconductor materials (PbTe,PbSe,PbS), a fluctuating temperature-dependent optical absorption edge is presented which is well associated with the calculated ab initio molecular dynamics output. A higher union temperature of 700, 900 and 1000 K for PbTe, PbSe and PbS is projected, as opposed to previous works involving the merging of primary and secondary bands at 400 K. This disassembly can influence the modeling of electronic properties by providing a tangible value for the valence band and the offset band gap as a function of temperature. The alternative thermoelectric material, ZrNiSn, is examined for both its electronic and optical properties. Conversely, the transport properties imply a substantially different band gap, depending on whether the material is p-type or n-type doped. By quantifying and testifying the optical band gap value of 0.13 eV, the inconsistency in the gap computed from the electronic properties can be resolved by associating these assessments with the weighted mobility ratio, A, in narrow gap materials. Due to its low thermal conductivity and adjustable electrical conductivity, Ternary Cu_2 SnSe_3 material with a diamond-like structure has been fitted as one of the latent thermoelectric materials. In this study, the Cu_2 SnSe_3 powder is produced by the vacuum melting-quenching-annealing-grinding process. Electrical resistance, Seebeck coefficient and thermal conductivity measurement are used for the analysis of thermoelectric properties.