In composite materials with nominal compositions Cu₂Ge_xSb₂Te_x+4 (11 ≤ x ≤ 18, i.e., between Cu_6.7Ge_36.7Sb_6.7Te₅₀ and Cu_4.5Ge_40.9Sb_4.5Te₅₀), precipitates consisting of copper tellurides are endotaxially intergrown in a matrix of Cu-doped germanium antimony tellurides. The precipitates as well as the matrix material undergo various phase transitions as shown by temperature-dependent X-ray diffraction and X-ray absorption contrast imaging. Eventually, the precipitates dissolve in the matrix at temperatures exceeding 580 °C. The temperature-dependent behavior was also traced by photoemission electron microscopy up to 460 °C. At high temperatures, the thermoelectric properties are superior to those of pure germanium antimony tellurides obtained by comparable syntheses; a maximal zT value of 1.83 for Cu₂Ge₁₆Sb₂Te₂₀ is reached at 500 °C. The application of an effective mass model reveals optimal charge carrier concentrations for all three compositions investigated. The p-type Cu₂Ge₁₆Sb₂Te₂₀ material was used in combination with PbTe:In (n-type) to construct a thermoelectric module. Concludingly, the measurement of the Hall effect that suggests no significant changes in Cu-doping levels of the matrix with temperature application of grain boundary optimization and a temperature-induced reset of the microstructure are proposed as strategies for overcoming material degradation upon applying electrical currents.

中文翻译：

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碲化铜在富 GeTe 锗锑碲化物中的内轴共生导致高热电性能

在复合材料中，标称成分为 Cu ₂ Ge _x Sb ₂ Te _{x +4} (11 ≤ x ≤ 18，即介于 Cu _6.7 Ge _36.7 Sb _6.7 Te ₅₀和 Cu _4.5 Ge _40.9 Sb _4.5 Te _50之间), 由铜碲化物组成的沉淀物在 Cu 掺杂的锗锑碲化物基质中内生共生。沉淀物以及基质材料经历各种相变，如温度相关的 X 射线衍射和 X 射线吸收对比成像所示。最终，沉淀物在超过 580 °C 的温度下溶解在基质中。还通过高达 460 °C 的光电子显微镜追踪了温度依赖性行为。在高温下，热电性能优于通过类似合成获得的纯锗锑碲；_{Cu 2} Ge ₁₆ Sb ₂ Te ₂₀的最大zT值为 1.83达到 500 °C。有效质量模型的应用揭示了所研究的所有三种组合物的最佳载流子浓度。p型 Cu ₂ Ge ₁₆ Sb ₂ Te ₂₀材料与 PbTe:In（n型）结合使用以构建热电模块。最后，霍尔效应的测量表明，随着晶界优化的温度应用和温度诱导的微观结构重置，基体的 Cu 掺杂水平没有显着变化，作为克服施加电流时材料退化的策略。