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Page 2 of 15 Xie et al. Energy Mater. 2025, 5, 500127 https://dx.doi.org/10.20517/energymater.2025.48

applications such as waste heat recovery, solid-state cooling, and remote power generation. Their operation
is governed by the Seebeck and Peltier effects, which facilitate the construction of solid-state thermal devices
without moving parts. Compared to conventional thermal engines, thermoelectric systems offer notable
advantages, including environmental friendliness, high reliability, and low maintenance requirements,
rendering them highly suitable for long-term and sustainable applications .
[1,2]
Thermoelectric materials are typically classified according to their optimal operating temperature ranges.
High-temperature materials, such as silicon-based alloys (e.g., SiGe, FeSi , and Mg Si), are employed in
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harsh or extreme environments. Mid-temperature chalcogenides, including PbTe and SnSe, are well-suited
for industrial-scale applications. In contrast, low-temperature materials - particularly Bi Te and its alloys -
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exhibit the highest efficiency near room temperature and are widely utilized in applications such as solid-
state cooling and small-scale power generation . Among these, Bi Te -based compounds are especially
[3,4]
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notable for their superior thermoelectric performance in the low-temperature regime .
[5]
Bismuth telluride (Bi Te )-based compounds represent one of the most extensively utilized classes of
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thermoelectric materials within the near-room-temperature range of 300-400 K, primarily due to their
favorable combination of high electrical conductivity and inherently low thermal conductivity.
Furthermore, these materials exhibit good chemical stability, can be synthesized with relative ease, and are
compatible with large-scale manufacturing processes. As a result of these desirable attributes, Bi Te -based
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materials are widely implemented in applications such as solid-state refrigeration and the recovery of low-
grade waste heat.
Traditional crystal growth techniques often lead to compositional segregation, resulting in material non-
uniformity and diminished thermoelectric efficiency . To address this issue, rapid solidification methods -
[6]
such as atomization and melt-spinning - have been developed to produce powders with uniform chemical
composition and nanoscale microstructures . Among these, atomization enables rapid cooling, yielding
[7-9]
fine powders (< 30 µm) with homogeneous elemental distribution. These powders can then be consolidated
into dense thermoelectric materials via sintering techniques such as spark plasma sintering (SPS) . The
[10]
resulting nanoscale grains significantly enhance phonon scattering, thereby reducing lattice thermal
conductivity and improving overall thermoelectric performance.

Although variations in melt-spun ribbon thickness occur due to different copper wheel speeds, previous
studies have shown that ribbon thickness does not significantly affect thermoelectric properties, including
electrical conductivity, Seebeck coefficient and the dimensionless figure of merit (ZT) [11,12] . This suggests that
even when ribbon thickness deviates from literature-reported values, the thermoelectric performance
remains largely unaffected. In our prior experiments, varying the duration of planetary ball milling revealed
that a milling time of 10 h produced the most homogeneous composition. Furthermore, the incorporation
of melt-spinning was found to be crucial, as evidenced by X-ray diffraction (XRD) results. Samples
subjected to melt-spinning exhibited sharper and more distinct peaks, indicating improved phase purity and
crystallinity, thereby highlighting the importance of this step in thermoelectric material synthesis.

Elemental composition also plays a significant role in optimizing thermoelectric performance. Increasing
antimony content was observed to enhance electrical conductivity; however, it also led to a reduction in the
Seebeck coefficient, ultimately lowering the power factor. Conversely, reducing tellurium content increased
electrical conductivity while slightly decreasing the Seebeck coefficient. Nevertheless, the overall ZT value
improved within the temperature range of 423-523 K, indicating that tellurium vacancies may contribute