High Pressure Drives Microstructure Modification and <i>zT</i> Enhancement in Bismuth Telluride-Based Alloys
Tu Lyu, Quanxin Yang, Zhenming Li, Chaohua Zhang, Fusheng Liu, Junqin Li, Lipeng Hu, Guiying Xu
Abstract
Manipulating and integrating the microstructures at different scales is crucial to tune the electrical and thermal properties of a given compound. High-pressure sintering can modify the multiscale microstructures and thus empower the cutting-edge thermoelectric performance. In this work, the high-pressure sintering technique followed by annealing is adopted to prepare Gd-doped p -type (Bi 0.2 Sb 0.8 ) 2 (Te 0.97 Se 0.03 ) 3 alloys. First, the high energy of high-pressure sintering promotes the reduction of grain size, thus increasing the content of 2D grain boundaries. Next, high-pressure sintering induces strong interior strain, where 1D dense dislocations are generated near the strain field. More interestingly, the rare-earth element Gd with a high melting temperature is dissolved into the matrix via high-pressure sintering, thus promoting the formation of 0D extrinsic point defects. This concurrently improves the carrier concentration and density-of-state effective mass, resulting in an enhanced power factor. In addition, the integrated 0D point defects, 1D dislocations, and 2D grain boundaries by high-pressure sintering strengthen phonon scattering, thereby achieving a low lattice thermal conductivity of 0.5 Wm –1 K –1 at 348 K. Consequently, a maximum zT value of ∼1.1 at 348 K is achieved in the 0.4 at % Gd-doped (Bi 0.2 Sb 0.8 ) 2 (Te 0.97 Se 0.03 ) 3 sample. This work demonstrates that high-pressure sintering enables microstructure modification to enhance the thermoelectric performance of Bi 2 Te 3 -based and other bulk materials.