Role of grain alignment and oxide impurity in thermoelectric properties of textured n-type Bi-Te-Se alloy

Rapaka S.C. Bose, Dilip K M, Paolo Mele, K. Ramesh

研究成果: Article査読

抄録

A nanostructured n-type Bi2Te2.7Se0.3 (BTS) alloy with a unique microstructure was prepared using a facile melting-rotation-quenching process followed by ball-milling and uniaxial hot-press sintering at 623 K. Anisotropy in the resulting microstructure showed anisotropic electrical and thermal transport properties in two directions normal to the pressing axis. The texture of the nanostructured BTS alloy was analyzed by x-ray diffraction and scanning electron microscopy. Based on the geometric phase analysis of a high resolution transmission electron microscopy images, abundant dislocations, high grain boundary density, and oxide impurity were identified, which act as phonon scattering centers. Higher anisotropy in thermal conductivity combined with oxide impurity resulted in an ultra-low phonon thermal conductivity of ∼0.305 W mK-1 at 423 K in the nanostructured n-type BTS in the direction parallel to the pressing axis. Laser power- and temperature-dependent Raman spectra analyses provided a deeper insight into the anisotropy in thermal transport properties. Optimum power factor and low thermal conductivity, due to the combination of grain alignment and oxide impurity, resulted in a dimensionless figure of merit (zT ) value of ∼0.75 at 423 K. In comparison, the high and opposite temperature dependences of electrical conductivity and thermal conductivity led to a better average zT value of ∼0.68 and a thermoelectric energy conversion efficiency percentage of ∼4.4% in the operating temperature range (300-423 K) in the direction parallel to the pressing axis.

本文言語English
論文番号235503
ジャーナルJournal of Physics D: Applied Physics
54
23
DOI
出版ステータスPublished - 2021 6 10

ASJC Scopus subject areas

  • 電子材料、光学材料、および磁性材料
  • 凝縮系物理学
  • 音響学および超音波学
  • 表面、皮膜および薄膜

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