Pathak Riddhimoy, Dutta Prabir, Srivastava Ashutosh, Rawat Divya, Gopal Radha Krishna, Singh Abhishek K, Soni Ajay, Biswas Kanishka
New Chemistry Unit, Jawaharlal Nehru Centre for Advanced Scientific Research (JNCASR) Jakkur P.O., Bangalore, 560064, India.
Materials Research Centre, Indian Institute of Science, Bangalore, 560012, India.
Angew Chem Int Ed Engl. 2022 Oct 10;61(41):e202210783. doi: 10.1002/anie.202210783. Epub 2022 Sep 2.
Intrinsically low lattice thermal conductivity (κ ) while maintaining the high carrier mobility (μ) is of the utmost importance for thermoelectrics. Topological insulators (TI) can possess high μ due to the metallic surface states. TIs with heavy constituents and layered structure can give rise to high anharmonicity and are expected to show low κ . Here, we demonstrate that Bi Sb Te S (BSTS), which is a 3D bulk TI, exhibits ultra-low κ of 0.46 Wm K along with high μ of ≈401 cm V s . Sound velocity measurements and theoretical calculations suggest that chemical bonding hierarchy and high anharmonicity play a crucial role behind such ultra-low κ . BSTS possesses low energy optical phonons which strongly couple with the heat carrying acoustic phonons leading to ultra-low κ . Further, Cl has been doped at the S site of BSTS which increases the electron concentration and reduces the κ resulting in a promising n-type thermoelectric figure of merit (zT) of ≈0.6 at 573 K.
对于热电材料而言，在保持高载流子迁移率（μ）的同时，本质上具有低的晶格热导率（κ）至关重要。拓扑绝缘体（TI）由于其金属表面态可具有高迁移率。具有重元素成分和层状结构的拓扑绝缘体可产生高非谐性，并有望表现出低κ。在此，我们证明作为三维体拓扑绝缘体的BiSbTeS（BSTS），展现出0.46 Wm⁻¹K的超低κ以及约401 cm²V⁻¹s的高μ。声速测量和理论计算表明，化学键层级和高非谐性在这种超低κ背后起着关键作用。BSTS拥有低能光学声子，其与携带热量的声学声子强烈耦合，导致超低κ。此外，Cl已被掺杂到BSTS的S位点，这增加了电子浓度并降低了κ，从而在573 K时产生了约0.6的有前景的n型热电品质因数（zT）。
