Strong Chemical Bond Hierarchy Leading to Exceptionally High Thermoelectric Figure of Merit in Oxychalcogenide AgBiTeO

Mukherjee, M and Singh, AK (2020) Strong Chemical Bond Hierarchy Leading to Exceptionally High Thermoelectric Figure of Merit in Oxychalcogenide AgBiTeO. In: ACS Applied Materials and Interfaces, 12 (7). pp. 8280-8287.

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Abstract

The chemical bond hierarchy (CBH) in prototype cage structures has been considered important for achieving high thermoelectric performance. By performing first-principles calculations and lattice dynamics, we demonstrate CBH hosted distinct rattlers in a noncaged oxychalcogenide AgBiTeO, causing an ultralow κl of 0.9 W/m-K at room temperature. The CBH in this compound leads to a unique structural bonding, where Ag and Te are loosely bonded to the rigid framework of the lattice and form distorted four-centered Ag-Te tetrahedra. These clusters exhibit large atomic vibrational motions in a very shallow potential energy surface, resulting in a rattling motion. The presence of multiple avoided crossing points of low-lying optical mode with longitudinal acoustic mode in phonon dispersion further confirms the rattling-induced thermal damping. Additionally, unique in-plane off-phase collective vibrations of Ag-Te tetrahedra introduce localized flat phonon dispersions that lower the group velocity and significantly reduce the lattice thermal conductivity. Most importantly, it prevents carrier-phonon scattering leading to a high electrical conductivity in AgBiTeO. The combination of intrinsic low lattice thermal conductivity and excellent electronic transport properties gives an unprecedented range of ZT from 1.00 to 1.99 in the large temperature range of 700-1200 K for n-type charge carriers.

Item Type:	Journal Article
Publication:	ACS Applied Materials and Interfaces
Publisher:	AMER Chemical Society
Additional Information:	The copyright of this article belongs to AMER Chemical Society
Keywords:	Acoustic dispersion; Bismuth compounds; Calculations; Chemical bonds; Geometry; Lattice vibrations; Phonons; Potential energy; Quantum chemistry; Silver compounds; Tellurium compounds; Thermoelectricity, cluster rattlers; Electronic transport properties; First-principles calculation; High electrical conductivity; Lattice thermal conductivity; Oxychalcogenides; Thermoelectric figure of merit; Thermoelectrics, Thermal conductivity, article; calculation; chemical bond; electric conductivity; human; human experiment; phonon; room temperature; thermal conductivity; vibration
Department/Centre:	Division of Chemical Sciences > Materials Research Centre
Date Deposited:	17 Jun 2020 06:21
Last Modified:	17 Jun 2020 06:21
URI:	http://eprints.iisc.ac.in/id/eprint/64820

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