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Ferroelectric Instability Induced Ultralow Thermal Conductivity and High Thermoelectric Performance in Rhombohedral p-type GeSe Crystal
Journal of the American Chemical Society ( IF 14.4 ) Pub Date : 2020-06-22 , DOI: 10.1021/jacs.0c03696 Debattam Sarkar , Tanmoy Ghosh , Subhajit Roychowdhury , Raagya Arora , Sandra Sajan 1 , Goutam Sheet 1 , Umesh V Waghmare , Kanishka Biswas
Journal of the American Chemical Society ( IF 14.4 ) Pub Date : 2020-06-22 , DOI: 10.1021/jacs.0c03696 Debattam Sarkar , Tanmoy Ghosh , Subhajit Roychowdhury , Raagya Arora , Sandra Sajan 1 , Goutam Sheet 1 , Umesh V Waghmare , Kanishka Biswas
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The orthorhombic phase of GeSe, a structural analogue of layered SnSe (space group: Pnma), has recently attracted attention after a theoretical prediction of high thermoelectric figure of merit, zT > 2. The experimental realization of such high performance in orthorhombic GeSe, however, is still elusive (zT ~0.2). The rhombohedral phase of GeSe, a structural analogue of GeTe (space group: R3m), previously stabilized at high pressure (2 GPa) and high temperature (1600 K), is promising due to its theoretically predicted ferroelectric instability and the higher earth abundance of Se compared to Te. Here, we demonstrate high thermoelectric performance in the rhombohedral crystals of GeSe, which is stabilized at ambient conditions by alloying with 10 mol% AgBiSe2. We show ultralow lattice thermal conductivity (kL) of 0.74-0.47 W/mK in the 300-723 K range and high zT = 1.25 at 723 K in the p-type rhombohedral (GeSe)0.9(AgBiSe2)0.1 crystals grown using Bridgman method. First-principles density functional theoretical (DFT) analysis reveals its vicinity to a ferroelectric instability which generates large anomalous Born effective charges and strong coupling of low energy polar optical phonons with acoustic phonons. The presence of soft optical phonons and incipient ferroelectric instability in (GeSe)0.9(AgBiSe2)0.1 are directly evident in the low temperature heat capacity (Cp) and switching spectroscopy piezoresponse force microscopy (SS-PFM) experiments, respectively. Effective scattering of heat carrying acoustic phonons by ferroelectric instability induced soft transverse optical phonons significantly reduces the kL and enhances the thermoelectric performance in rhombohedral (GeSe)0.9(AgBiSe2)0.1 crystals.
中文翻译：
菱形p型GeSe晶体中铁电不稳定性引起的超低热导率和高热电性能
GeSe 的正交相是层状 SnSe（空间群：Pnma）的结构类似物，最近在对高热电品质因数 zT > 2 的理论预测后引起了人们的关注。然而，在正交 GeSe 中这种高性能的实验实现, 仍然难以捉摸 (zT ~0.2)。GeSe 的菱形相是 GeTe 的结构类似物（空间群：R3m），以前在高压 (2 GPa) 和高温 (1600 K) 下稳定，由于其理论上预测的铁电不稳定性和较高的地球丰度Se 与 Te 相比。在这里，我们展示了 GeSe 菱形晶体的高热电性能，通过与 10 mol% AgBiSe2 合金化，GeSe 在环境条件下稳定。我们展示了 0.74-0 的超低晶格热导率 (kL)。使用布里奇曼方法生长的 p 型菱形 (GeSe)0.9(AgBiSe2)0.1 晶体在 300-723 K 范围内为 47 W/mK，在 723 K 时 zT = 1.25。第一性原理密度泛函理论 (DFT) 分析揭示了其邻近铁电不稳定性，该不稳定性产生大量异常玻恩有效电荷和低能量极性光学声子与声学声子的强耦合。(GeSe)0.9(AgBiSe2)0.1 中软光学声子的存在和初始铁电不稳定性分别在低温热容 (Cp) 和开关光谱压电响应力显微镜 (SS-PFM) 实验中直接明显。
更新日期：2020-06-22
中文翻译：
菱形p型GeSe晶体中铁电不稳定性引起的超低热导率和高热电性能
GeSe 的正交相是层状 SnSe（空间群：Pnma）的结构类似物，最近在对高热电品质因数 zT > 2 的理论预测后引起了人们的关注。然而，在正交 GeSe 中这种高性能的实验实现, 仍然难以捉摸 (zT ~0.2)。GeSe 的菱形相是 GeTe 的结构类似物（空间群：R3m），以前在高压 (2 GPa) 和高温 (1600 K) 下稳定，由于其理论上预测的铁电不稳定性和较高的地球丰度Se 与 Te 相比。在这里，我们展示了 GeSe 菱形晶体的高热电性能，通过与 10 mol% AgBiSe2 合金化，GeSe 在环境条件下稳定。我们展示了 0.74-0 的超低晶格热导率 (kL)。使用布里奇曼方法生长的 p 型菱形 (GeSe)0.9(AgBiSe2)0.1 晶体在 300-723 K 范围内为 47 W/mK，在 723 K 时 zT = 1.25。第一性原理密度泛函理论 (DFT) 分析揭示了其邻近铁电不稳定性，该不稳定性产生大量异常玻恩有效电荷和低能量极性光学声子与声学声子的强耦合。(GeSe)0.9(AgBiSe2)0.1 中软光学声子的存在和初始铁电不稳定性分别在低温热容 (Cp) 和开关光谱压电响应力显微镜 (SS-PFM) 实验中直接明显。
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