Vaishali Taneja

Jawaharlal Nehru Centre for Advanced Scientific Research

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Kanishka Biswas

Jawaharlal Nehru Centre for Advanced Scientific Research

Debattam Sarkar

Jawaharlal Nehru Centre for Advanced Scientific Research

Abdul Ahad

Shifa Tameer-e-Millat University

Kapildeb Dolui

University of Cambridge

Subarna Das

Jawaharlal Nehru Centre for Advanced Scientific Research

Koushik Pal

Jawaharlal Nehru Centre for Advanced Scientific Research

Moinak Dutta

Jawaharlal Nehru Centre for Advanced Scientific Research

S. O. Manjunatha

Jawaharlal Nehru Centre for Advanced Scientific Research

Diptikanta Swain

Indian Institute of Technology Bhubaneswar

Manisha Samanta

Jawaharlal Nehru Centre for Advanced Scientific Research

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Jawaharlal Nehru Centre for Advanced Scientific Research

Bangalore University

Indian Institute of Science Bangalore

University of Calcutta

Northwestern University

Sheikh Saqr Laboratory

Indian Association for the Cultivation of Science

UGC DAE Consortium for Scientific Research

The Ohio State University

Indian Institute of Science Education and Research Mohali

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High Thermoelectric Performance in Phonon‐Glass Electron‐Crystal Like AgSbTe₂

Advanced Materials (2023)

Vaishali Taneja Subarna Das Kapildeb Dolui Tanmoy Ghosh Animesh Bhui

Abstract Achieving glass‐like ultra‐low thermal conductivity in crystalline solids with high electrical conductivity, a crucial requirement for high‐performance thermoelectrics , continues to be a formidable challenge. A careful balance between electrical and thermal transport is essential for optimizing the thermoelectric performance. Despite this inherent trade‐off, the experimental realization of an ideal thermoelectric material with a phonon‐glass electron‐crystal (PGEC) nature has rarely been achieved. Here, PGEC‐like AgSbTe 2 is demonstrated by tuning the atomic disorder upon Yb doping, which results in an outstanding thermoelectric performance with figure of merit, zT ≈ 2.4 at 573 K. Yb‐doping‐induced enhanced atomic ordering decreases the overlap between the hole and phonon mean free paths and consequently leads to a PGEC‐like transport behavior in AgSbTe 2 . A twofold increase in electrical mobility is observed while keeping the position of the Fermi level ( E F ) nearly unchanged and corroborates the enhanced crystalline nature of the AgSbTe 2 lattice upon Yb doping for electrical transport. The cation‐ordered domains, lead to the formation of nanoscale superstructures (≈2 to 4 nm) that strongly scatter heat‐carrying phonons, resulting in a temperature‐independent glass‐like thermal conductivity. The strategy paves the way for realizing high thermoelectric performance in various disordered crystals by making them amorphous to phonons while favoring crystal‐like electrical transport.

Figure of Merit

Crystal (programming language)

10.1002/adma.202307058

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Citations (33)

Chemical Bonding Tuned Lattice Anharmonicity Leads to a High Thermoelectric Performance in Cubic AgSnSbTe₃

Angewandte Chemie International Edition (2023)

Debattam Sarkar Kapildeb Dolui Vaishali Taneja Abdul Ahad Moinak Dutta

Abstract Comprehension of chemical bonding and its intertwined relation with charge carriers and heat propagation through a crystal lattice is imperative to design compounds for thermoelectric energy conversion. Here, we report the synthesis of large single crystal of new p ‐type cubic AgSnSbTe 3 which shows an innately ultra‐low lattice thermal conductivity (κ lat ) of 0.47–0.27 Wm −1 K −1 and a high electrical conductivity (1238 – 800 S cm −1 ) in the temperature range 294–723 K. We investigated the origin of the low κ lat by analysing the nature of the chemical bonding and its crystal structure. The interaction between Sn(5 s )/Ag(4 d ) and Te(5 p ) orbitals was found to generate antibonding states just below the Fermi level in the electronic band structure, resulting in a softening of the lattice in AgSnSbTe 3 . Furthermore, the compound exhibits metavalent bonding which provides highly polarizable bonds with a strong lattice anharmonicity while maintaining the superior electrical conductivity. The electronic band structure exhibits nearly degenerate valence‐band maxima that help to achieve a high Seebeck coefficient throughout the measured temperature range and, as a result, the maximum thermoelectric figure of merit reaches to ≈1.2 at 661 K in pristine single crystal of AgSnSbTe 3 .

Antibonding molecular orbital

10.1002/anie.202308515

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Chemical Bonding Tuned Lattice Anharmonicity Leads to a High Thermoelectric Performance in Cubic AgSnSbTe₃

Angewandte Chemie (2023)

Debattam Sarkar Kapildeb Dolui Vaishali Taneja Abdul Ahad Moinak Dutta

Antibonding molecular orbital

10.1002/ange.202308515

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Glassy Thermal Transport Triggers Ultra‐High Thermoelectric Performance in GeTe

Advanced Materials (2025)

Debattam Sarkar Subarna Das Vaishali Taneja Manisha Samanta Koushik Jagadish

Abstract The consequences of broken long‐range atomic arrangement in glasses or amorphous solids are reflected in the temperature dependence of lattice thermal conductivity (κ lat ). However, the appearance of glassy ultralow κ lat in a crystalline solid with high electrical transport like metal is unusual but can have a remarkable impact on the thermoelectric performance of a material. Here, an ultra‐high thermoelectric performance is demonstrated with a maximum figure of merit, zT ≈ 2.7 (≈2.92 with Dulong–Petit heat capacity) via achieving glassy thermal transport along with significant electrical conductivity in ball milled BiSe, Pb co‐doped polycrystalline Ge 1.03 Te followed by spark plasma sintering. The glassy thermal transport results from the inhomogeneous ferroelectric instability developed due to local polar distortions near the dopant sites, which interacts with soft polar optical modes via strain fluctuations. Resulting structural degeneracy and associated soft vibrations sink heat effectively from acoustic phonons, which along with various nanoscale defects, confine the phonon mean free path (MFP) close to the interatomic distance, rendering the thermal transport glassy. However, the material still maintains a high electrical conductivity at ambient condition due to much longer MFP of the charge carriers. A promising output power density of ≈0.8 W cm −2 for ΔT ≈441 K in double‐leg thermoelectric device demonstrate the potential of this material for mid‐temperature thermoelectric applications.

Spark Plasma Sintering

10.1002/adma.202417561

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Coexistence of quantum diffusive and diffusive two band carriers in site disordered AgSnSbTe3

Materials Today Physics (2022)

Abdul Ahad Debattam Sarkar Vaishali Taneja Kanishka Biswas

Charge carrier

Weak localization

10.1016/j.mtphys.2022.100787

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Nanostructured Ferecrystal Intergrowths with TaSe₂ Unveiled High Thermoelectric Performance in n-Type SnSe

Journal of the American Chemical Society (2024)

Vaishali Taneja Naveen Goyal Subarna Das Sushmita Chandra Prabir Dutta

Ferecrystals, a distinctive class of misfit layered compounds, hold significant promise in manipulating the phonon transport owing to their two-dimensional (2D) natural superlattice-type structure and turbostratic (rotational) disorder present between the constituent layers. Integrating these 2D intergrowth structures as nanodomains embedded in a bulk thermoelectric matrix is a formidable challenge in synthetic chemistry, yet offers groundbreaking opportunities for efficient thermoelectrics. Here, we have achieved an exceptionally high thermoelectric figure of merit, zT ∼ 2.2, at 823 K in n-type Ta and Br-codoped SnSe, by successfully incorporating [(SnSe)1.15]7(TaSe2)1 ferecrystals with [110] SnSe//[100] TaSe2 orientation, as nanostructures with modulations in few nm in bulk SnSe solid-state matrix. While the presence of ferecrystal nanostructures induces strong scattering of heat-carrying phonons resulting in an ultralow lattice thermal conductivity (κL) of ∼0.18 W m–1 K–1 at 773 K, the Ta and Br codoping strategy increases the concentration of n-type charge carriers for enhanced electrical conductivity. Our approach provides a new pathway for damping the phonon transport and enhancing the thermoelectric performance in 2D layered materials.

Phonon scattering

Figure of Merit

10.1021/jacs.4c09943

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Citations (4)