Vacancy manipulation for thermoelectric enhancements in GeTe alloys,Journal of the American Chemical Society

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Vacancy manipulation for thermoelectric enhancements in GeTe alloys
Journal of the American Chemical Society ( IF 14.4 ) Pub Date : 2018-09-28 , DOI: 10.1021/jacs.8b09375
Xinyue Zhang ₁ , Juan Li ₁ , Xiao Wang ₁ , Zhiwei Chen ₁ , Jianjun Mao ₂ , Yue Chen ₂ , Yanzhong Pei ₁

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Optimization of carrier concentration plays an important role on maximizing thermoelectric performance. Existing efforts mainly focus on aliovalent doping, while intrinsic defects (e.g., vacancies) provide extra possibilities. Thermoelectric GeTe intrinsically forms in off-stoichiometric with Ge-vacancies and Ge-precipitates, leading to a hole concentration significantly higher than required. In this work, Sb2Te3 having a smaller cation-to-anion ratio, is used as a solvend to form solid solutions with GeTe for manipulating the vacancies. This is enabled by the fact that each substitution of 3 Ge2+ by only 2 Sb3+ creates 1 Ge vacancy, because of the overall 1:1 cation-to-anion ratio of crystallographic sites in the structure and by the charge neutrality. The increase in the overall Ge-vacancy concentration facilitates Ge-precipitates to be dissolved into the matrix for reducing the hole concentration. In a combination with known reduction in hole concentration by Pb/Ge-substitution, a full optimization on hole concentration is realized. In addition, the resultant high-concentration point defects including both vacancies and substitutions strongly scatter phonons and reduce the lattice thermal conductivity to the amorphous limit. These enable a significantly improved thermoelectric figure of merit at working temperatures of thermoelectric GeTe.

中文翻译：

GeTe合金中热电增强的空位操作

载流子浓度的优化对于最大化热电性能起着重要作用。现有的努力主要集中在异价掺杂上，而内在缺陷（例如空位）提供了额外的可能性。热电 GeTe 本质上与 Ge 空位和 Ge 沉淀物以非化学计量形式形成，导致空穴浓度显着高于所需。在这项工作中，使用具有较小阳离子与阴离子比的 Sb2Te3 作为溶剂与 GeTe 形成固溶体以控制空位。这是因为每次 3 Ge2+ 仅被 2 Sb3+ 取代会产生 1 Ge 空位，这是因为结构中结晶位点的总体阳离子与阴离子比为 1:1，并且电荷中性。整体 Ge 空位浓度的增加有利于 Ge 沉淀物溶解到基质中以降低空穴浓度。结合已知的 Pb/Ge 替代降低空穴浓度，实现了空穴浓度的全面优化。此外，由此产生的包括空位和取代在内的高浓度点缺陷强烈散射声子并将晶格热导率降低到非晶极限。这些能够在热电 GeTe 的工作温度下显着改善热电品质因数。由此产生的高浓度点缺陷包括空位和取代强烈散射声子并将晶格热导率降低到非晶极限。这些能够在热电 GeTe 的工作温度下显着改善热电品质因数。由此产生的高浓度点缺陷包括空位和取代强烈散射声子并将晶格热导率降低到非晶极限。这些能够在热电 GeTe 的工作温度下显着改善热电品质因数。

更新日期：2018-09-28

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