Acharyya Paribesh, Roychowdhury Subhajit, Samanta Manisha, Biswas Kanishka
New Chemistry Unit, Jawaharlal Nehru Centre for Advanced Scientific Research (JNCASR), Jakkur P.O., Bangalore 560064, India.
School of Advanced Materials and International Centre for Materials Science, Jawaharlal Nehru Centre for Advanced Scientific Research (JNCASR), Jakkur P.O., Bangalore 560064, India.
J Am Chem Soc. 2020 Nov 20. doi: 10.1021/jacs.0c11015.
Thermoelectric (TE) energy conversion demands high performance crystalline inorganic solids that exhibit ultralow thermal conductivity, high mechanical stability, and good TE device properties. Pb-free germanium telluride (GeTe)-based material has recently attracted significant attention in TE power generation in mid temperatures, but pristine GeTe possesses significantly higher lattice thermal conductivity (κ) compared to that of its theoretical minimum (κ) of ∼0.3 W/mK. Herein, we have demonstrated the reduction of κ of (GeTe)(SnSe)(SnS) very near to its κ. The (GeTe)(SnSe)(SnS) system behaves as a coexistence of point-defect rich solid solution and phase separation. Initially, the addition of equimolar SnSe and SnS in the GeTe reduces the κ by effective phonon scattering because of the excess point defects and rich microstructures. In the second step, introduction of Sb-doping leads to additional phonon scattering centers and optimizes the -type carrier concentration. Notably, 10 mol % Sb-doped (GeTe)(SnSe)(SnS) exhibits ultralow κ of ∼0.30 W/mK at 300 K. Subsequently, 10 mol % Sb-doped (GeTe)(SnSe)(SnS) exhibits a high TE figure of merit (zT) of ∼1.9 at 710 K. The high-performance sample exhibits a Vickers microhardness (mechanical stability) value of ∼194 that is significantly higher compared to the pristine GeTe and other state-of-the-art thermoelectric materials. Further, we have achieved a high output power, ∼150 mW for the temperature difference of 462 K, in single leg TE device based on 10 mol % Sb-doped (GeTe)(SnSe)(SnS).
热电（TE）能量转换需要高性能的晶体无机固体，这些固体要表现出超低的热导率、高机械稳定性和良好的TE器件性能。无铅碲化锗（GeTe）基材料最近在中温TE发电领域引起了极大关注，但原始的GeTe的晶格热导率（κ）与其理论最小值（κ）约0.3W/mK相比要高得多。在此，我们已证明（GeTe）（SnSe）（SnS）的κ降低至非常接近其理论最小值。（GeTe）（SnSe）（SnS）体系表现为富含点缺陷的固溶体和相分离的共存。最初，在GeTe中添加等摩尔的SnSe和SnS由于过量的点缺陷和丰富的微观结构而通过有效的声子散射降低了κ。在第二步中，引入Sb掺杂导致额外的声子散射中心并优化了n型载流子浓度。值得注意的是，10mol% Sb掺杂的（GeTe）（SnSe）（SnS）在300K时表现出约0.30W/mK的超低κ。随后，10mol% Sb掺杂的（GeTe）（SnSe）（SnS）在710K时表现出约1.9的高热电优值（zT）。该高性能样品表现出约194的维氏显微硬度（机械稳定性）值，与原始GeTe和其他现有热电材料相比显著更高。此外，我们基于10mol% Sb掺杂的（GeTe）（SnSe）（SnS）在单腿TE器件中实现了462K温差下约150mW的高输出功率。
