The Improvement Of Thermoelectric Performance Of InTe By Microstructure Modification And Power Generation Devices

Approximately 90%of the energy from industrial waste heat is distributed below316℃,and the use of thermoelectric power generation technology has broad application prospects in the field of waste heat recovery and reuse by directly converting thermal energy into electrical energy.In the past decade,research on thermoelectric materials has focused on the region above 300℃,and there is a lack of exploration of new thermoelectric materials below intermediate temperatures.InTe-based thermoelectric materials have higher electrical conductivity and lower thermal conductivity along their[110]direction,and exhibit intrinsic thermal conductivity close to the amorphous limit due to the asymmetric chemical bonding and lattice anharmonicity.Current research mainly focuses on regulating lattice thermal conductivity and element doping on performance,but lacks research on carrier scattering mechanisms and utilizing anisotropy to improve polycrystalline performance.Therefore,this study investigates the scattering mechanism of polycrystalline InTe at room temperature and the effect of high orientation on polycrystalline.In response to the poor electrical properties of polycrystalline InTe,InTe polycrystalline samples with different grain sizes were prepared and comprehensively tested,revealing that grain boundary scattering（GBS）is the main reason for poor polycrystalline performance.Increasing grain size to suppress GBS can significantly improve the thermoelectric performance near room temperature.To address the issue of extremely poor mechanical properties of InTe single crystals,polycrystalline samples with high orientation and high mechanical properties were prepared by single crystal hot deformation,achieving the highest z T value of InTe-based thermoelectric materials at room temperature.By doping InTe with Pb,it is found that Pb will occupy the In⁺site.The cell parameters were refined based on the XRD data show that the lattice gradually decreases with the increase in the Pb doping concentration,and the carrier concentration of the sample decreases monotonically.Strong GBS still occurs when the sample has a large size and low carrier concentration(<0.7×10¹⁹ cm^-3).Meanwhile,Pb_0.0001In_0.9999Te achieves an improved power factor and an average z T value of 0.49 in the range of 300-623 K by properly optimizing the carrier concentration by doping,which is beneficial for power generation below intermediate temperatures.Through optimized design of the InTe-Bi₂Te_2.7Se_0.3 thermoelectric generator using COMSOL,the optimal device size with the highest conversion efficiency was obtained,and the actual device was successfully integrated.However,the untreated interface layer is the main reason for the difference between the device efficiency and simulation,and it is predicted that a good interface layer can achieve higher conversion efficiency.This thesis systematically investigated the poor electrical properties of polycrystalline InTe near room temperature due to strong GBS and proposed two optimization schemes.At the same time,through actual verification of the InTe-based thermoelectric power generation device,it has been demonstrated that this material has great potential.