Abstract

Silicon-germanium (SiGe) alloys are prominent high-temperature thermoelectric (TE) materials used as a powering source for deep space applications. In this work, we employed rapid cooling rates for solidification by melt-spinning and rapid heating rates for bulk consolidation employing spark plasma sintering to synthesize high-performance p-type SiGe nano-alloys. The current methodology exhibited a TE figure-of-merit (ZT) ≈ 0.94 at 1123 K for a higher cooling rate of ∼3.0 × 10⁷ K/s. This corresponds to ≈ 88% enhancement in ZT when compared with currently used radioisotope thermoelectric generators (RTGs) in space flight missions, ≈ 45% higher than pressure-sintered p-type alloys, which results in a higher output power density, and TE conversion efficiency (η) ≈ 8% of synthesized SiGe nano-alloys estimated using a cumulative temperature dependence (CTD) model. The ZT enhancement is driven by selective scattering of phonons rather than of charge carriers by the high density of grain boundaries with random orientations and induced lattice-scale defects, resulting in a substantial reduction of lattice thermal conductivity and high power factor. The TE characteristics of synthesized alloys presented using the constant property model (CPM) and CTD model display their high TE performance in high-temperature regimes along with wide suitability of segmentation with different mid-temperature TE materials.

Graphic Abstract

中文翻译：

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熔纺SiGe纳米合金：朝着高热电效率的微结构工程

摘要

硅锗（SiGe）合金是杰出的高温热电（TE）材料，可用作深空应用的动力源。在这项工作中，我们采用了通过熔体纺丝进行凝固的快速冷却速率，以及采用火花等离子烧结来合成高性能p型SiGe纳米合金的整体固结采用了快速加热速率。当前的方法在1123 K时表现出TE品质因数（ZT）≈0.94，而更高的冷却速率约为3.0×10 ⁷  K / s。与目前在太空飞行任务中使用的放射性同位素热电发生器（RTG）相比，这相当于ZT的≈88％的提高，比压力烧结的p高出45％型合金，可产生更高的输出功率密度，并且使用累积温度依赖性（CTD）模型估算出的合成SiGe纳米合金的TE转换效率（η）≈8％。ZT增强是由声子而不是电荷载流子的选择性散射所驱动，这是由于具有随机取向和诱发晶格尺度缺陷的高密度晶界引起的，从而大大降低了晶格导热率和高功率因数。使用恒定特性模型（CPM）和CTD模型显示的合成合金的TE特性显示了其在高温状态下的高TE性能，以及适用于不同中温TE材料进行分段的广泛适用性。

图形摘要