New Chemistry Unit, Jawaharlal Nehru Centre for Advanced Scientific Research (JNCASR), Jakkur P.O., Bangalore, India.
Theoretical Sciences Unit, Jawaharlal Nehru Centre for Advanced Scientific Research (JNCASR), Jakkur P.O., Bangalore, 560 064, India.
Angew Chem Int Ed Engl. 2016 Jun 27;55(27):7792-6. doi: 10.1002/anie.201511737. Epub 2016 Feb 25.
Understanding the origin of intrinsically low thermal conductivity is fundamentally important to the development of high-performance thermoelectric materials, which can convert waste-heat into electricity. Herein, we report an ultralow lattice thermal conductivity (ca. 0.4 W m(-1) K(-1) ) in mixed valent InTe (that is, In(+) In(3+) Te2 ), which exhibits an intrinsic bonding asymmetry with coexistent covalent and ionic substructures. The phonon dispersion of InTe exhibits, along with low-energy flat branches, weak instabilities associated with the rattling vibrations of In(+) atoms along the columnar ionic substructure. These weakly unstable phonons originate from the 5s(2) lone pair of the In(+) atom and are strongly anharmonic, which scatter the heat-carrying acoustic phonons through strong anharmonic phonon-phonon interactions, as evident in anomalously high mode Grüneisen parameters. A maximum thermoelectric figure of merit (z T) of about 0.9 is achieved at 600 K for the 0.3 mol % In-deficient sample, making InTe a promising material for mid-temperature thermoelectric applications.
理解固有低热导率的起源对于开发高性能热电材料至关重要，这些材料可以将废热转化为电能。在此，我们报告了混合价 InTe（即 In(+) In(3+) Te2）中极低的晶格热导率（约 0.4 W m(-1) K(-1)），其表现出固有键合不对称性，存在共存的共价和离子亚结构。InTe 的声子色散表现出低能平面支，与沿柱状离子亚结构的 In(+)原子的颤动振动相关的弱不稳定性。这些弱不稳定的声子源自 In(+)原子的 5s(2)孤对电子，它们具有强烈的非谐性，通过强烈的非谐声子-声子相互作用散射载热声子，这在异常高的模式格林艾森参数中表现明显。对于 0.3 mol%的 In 缺陷样品，在 600 K 时获得了约 0.9 的最大热电优值（zT），这使得 InTe 成为中温热电应用的有前途的材料。
