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

Bose, RSC and Dilip, KM and Mele, P and Ramesh, K (2021) Role of grain alignment and oxide impurity in thermoelectric properties of textured n-type Bi-Te-Se alloy. In: Journal of Physics D: Applied Physics, 54 (23).

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Abstract

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. © 2021 IOP Publishing Ltd.

Item Type:	Journal Article
Publication:	Journal of Physics D: Applied Physics
Publisher:	IOP Publishing Ltd
Additional Information:	The copyright for this article belongs to IOP Publishing Ltd
Keywords:	Alignment; Anisotropy; Ball milling; Bismuth alloys; Conversion efficiency; Grain boundaries; High resolution transmission electron microscopy; Phonons; Scanning electron microscopy; Sintering; Temperature distribution; Textures; Thermoelectric energy conversion; Thermoelectricity, Dimensionless figure of merit; Geometric phase analysis; Grain boundary densities; Low thermal conductivity; Operating temperature ranges; Temperature-dependent raman; Thermal transport properties; Thermoelectric properties, Thermal conductivity
Department/Centre:	Division of Physical & Mathematical Sciences > Physics
Date Deposited:	15 Jul 2021 05:49
Last Modified:	15 Jul 2021 05:49
URI:	http://eprints.iisc.ac.in/id/eprint/68780

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