Dramatically Enhanced Mechanical Properties of Nano-TiN-Dispersed n-Type Bismuth Telluride by Multi-Effect Modulation

• Published in: Materials Vol. 17; no. 8; p. 1919
• Main Authors: Lin, Shengao, Li, Jing, Yan, Heng, Meng, Xianfu, Xiang, Qingpei, Jing, Hang, Chen, Xiaoxi, Yang, Chuting
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 01.04.2024
• Subjects: Bend strength; Bismuth; Bismuth tellurides; Composite materials; Compressive strength; Crack propagation; Electric power production; Electric properties; Electrical conductivity; Energy harvesting; Figure of merit; Force and energy; Grain growth; Grain refinement; Grain size; Heat conductivity; Ingots; Intermetallic compounds; Mechanical properties; Modulation; nano-TiN dispersion; Nanoparticles; Pinning; pinning effect; Plasma sintering; Scanning electron microscopy; Thermoelectric materials; Thermoelectricity; Japan; Germany; grain refinement; nano-TiN dispersion; thermoelectric materials; bismuth tellurides; pinning effect; mechanical properties
• ISSN: 1996-1944; 1996-1944
• DOI: 10.3390/ma17081919

Bismuth telluride (Bi Te )-based alloys have been extensively employed in energy harvesting and refrigeration applications for decades. However, commercially produced Bi Te -based alloys using the zone-melting (ZM) technique often encounter challenges such as insufficient mechanical properties and susceptibility to cracking, particularly in n-type Bi Te -based alloys, which severely limit the application scenarios for bismuth telluride devices. In this work, we seek to enhance the mechanical properties of n-type Bi Te Se alloys while preserving their thermoelectrical performance by a mixed mechanism of grain refinement and the TiN composite phase-introduced pinning effect. These nanoscale processes, coupled with the addition of TiN, result in a reduction in grain size. The pinning effects of nano-TiN contribute to increased resistance to crack propagation. Finally, the TiN-dispersed Bi Te Se samples demonstrate increased hardness, bending strength and compressive strength, reaching 0.98 GPa, 36.3 MPa and 74 MPa. When compared to the ZM ingots, those represent increments of 181%, 60% and 67%, respectively. Moreover, the thermoelectric performance of the TiN-dispersed Bi Te Se samples is identical to the ZM ingots. The samples exhibit a peak dimensionless figure of merit ( ) value of 0.957 at 375 K, with an average value of 0.89 within the 325-450 K temperature range. This work has significantly enhanced mechanical properties, increasing the adaptability and reliability of bismuth telluride devices for various applications, and the multi-effect modulation of mechanical properties demonstrated in this study can be applied to other thermoelectric material systems.