Thermoelectric Properties of Cu-doped Bi0.4Sb1.6Te3 Prepared by Hot Extrusion

• Published in: Journal of electronic materials 2018-06, Vol.47 (6), p.3136-3142
• Main Authors: Jung, Woo-Jin, Kim, Il-Ho
• Format: Article
• Language: English
• Subjects: Bend strength; Characterization and Evaluation of Materials; Chemistry and Materials Science; Coefficients; Conduction cooling; Conduction heating; Crystallography; Diamond pyramid hardness; Electric properties; Electrical resistivity; Electronics and Microelectronics; Extrusion; Figure of merit; Hot extrusion; Instrumentation; International Conference on Thermoelectrics 2017; Materials Science; Mechanical properties; Optical and Electronic Materials; Planes; Solid State Physics; Thermal conductivity; Topical Collection: International Conference on Thermoelectrics 2017
• ISSN: 0361-5235; 1543-186X
• DOI: 10.1007/s11664-017-5840-y

Cu 0.003 Bi 0.4 Sb 1.6 Te 3 alloys were prepared by using encapsulated melting and hot extrusion (HE). The hot-extruded specimens had the relative average density of 98%. The ( 00l ) planes were preferentially oriented parallel to the extrusion direction, but the specimens showed low crystallographic anisotropy with low orientation factors. The specimens were hot-extruded at 698 K, and they showed excellent mechanical properties with a Vickers hardness of 76 Hv and a bending strength of 59 MPa. However, as the HE temperature increased, the mechanical properties degraded due to grain growth. The hot-extruded specimens showed positive Seebeck coefficients, indicating that the specimens have p -type conduction. These specimens exhibited negative temperature dependences of electrical conductivity, and thus behaved as degenerate semiconductors. The Seebeck coefficient reached the maximum value at 373 K and then decreased with increasing temperature due to intrinsic conduction. Cu-doped specimens exhibited high power factors due to relatively higher electrical conductivities and Seebeck coefficients than those of undoped specimens. A thermal conductivity of 1.00 Wm −1  K −1 was obtained at 373 K for Cu 0.003 Bi 0.4 Sb 1.6 Te 3 hot-extruded at 723 K. A maximum dimensionless figure of merit, ZT max  = 1.05, and an average dimensionless figure of merit, ZT ave  = 0.98, were achieved at 373 K.