Uniaxial‐Stress Driven Performance Enhancement of Multi‐Beam Spark Plasma Sintered BiSbTe/Epoxy Flexible Films

Abstract The multi‐beam discharge plasma sintering (MB‐SPS) method is successfully applied to the preparation of Bi2Te3‐based thermoelectric (TE) films with insulating substrates. Herein, the impact of uniaxial stress on the microstructure evolution and TE performance are explored systematically. The results indicate that the increase of uniaxial stress promotes the preferential growth of Bi0.5Sb1.5Te3 (BST) grains along the (000l) crystal plane, leading to the remarkable increase in carrier mobility. The maximum (000l) preferential orientation factor reaches 80% for the BST/epoxy (EP) film sintered under 25 MPa, which is 3.08 times higher than that of BST/EP film sintered at 10 MPa. While the highest power factor reaches 2.36 mW m−1 K−2 at 300 K for the BST/EP film sintered under 20 MPa, increased by 97% as compared with that of the film sintered under 10 MPa. This work once again confirms that the MB‐SPS technology is an effective approach to prepare high‐performance Bi2Te3‐based films with insulating substrates and demonstrates that the (000l) preferential orientation and TE performance of the films can be further enhanced by an appropriate uniaxial stress.