A record high zT of 2.2 at 740 K is reported in Ge_0.92Sb_0.08Te single crystals, with an optimal hole carrier concentration ≈4 × 10²⁰ cm⁻³ that simultaneously maximizes the power factor (PF) ≈56 µW cm⁻¹ K⁻² and minimizes the thermal conductivity ≈1.9 Wm⁻¹ K⁻¹. In addition to the presence of herringbone domains and stacking faults, the Ge_0.92Sb_0.08Te exhibits significant modification to phonon dispersion with an extra phonon excitation around ≈5–6 meV at Γ point of the Brillouin zone as confirmed through inelastic neutron scattering (INS) measurements. Density functional theory (DFT) confirmed this phonon excitation, and predicted another higher energy phonon excitation ≈12–13 meV at W point. These phonon excitations collectively increase the number of phonon decay channels leading to softening of phonon frequencies such that a three‐phonon process is dominant in Ge_0.92Sb_0.08Te, in contrast to a dominant four‐phonon process in pristine GeTe, highlighting the importance of phonon engineering approaches to improving thermoelectric (TE) performance.

中文翻译：

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Sb 掺杂 GeTe 单晶的高 zT 及其起源

_{Ge 0.92} Sb _0.08 Te 单晶在 740 K 下的zT达到创纪录的 2.2，最佳空穴载流子浓度 ≈4 × 10 ²⁰ cm ^-3，同时最大化功率因数 ( PF ) ≈56 µW cm ^-1  K ^-2并最小化热导率 ≈1.9 Wm ^-1 K ^-1。除了存在人字形域和堆垛层错之外，Ge _0.92 Sb _0.08 Te 还表现出对声子色散的显着改变，在布里渊区的Γ点处具有约 5–6 meV 的额外声子激发，这一点通过非弹性中子散射 (INS) 得到了证实。 ） 测量。密度泛函理论（DFT）证实了这种声子激发，并预测在W点有另一个更高能量的声子激发 ≈12–13 meV。这些声子激发共同增加了声子衰变通道的数量，导致声子频率软化，使得三声子过程在 Ge _0.92 Sb _0.08 Te 中占主导地位，与原始 GeTe 中占主导地位的四声子过程形成鲜明对比，突出了提高热电 ( TE ) 性能的声子工程方法。