In this work, eco-friendly magnesium-silicide (Mg₂Si) semiconducting (n-type) thermoelectric pastes for building components concerning energy-harvesting devices through 3D printing, spray and electrospinning were synthetized and tested for the first time. The Mg₂Si fine powders were obtained through the combination of ball milling and thermal annealing under Ar atmosphere. While the latter process was crucial for obtaining the desired Mg₂Si phase, the ball milling was indispensable for homogenizing and reducing the grain size of the powders. The synthetized Mg₂Si powders exhibited a large Seebeck coefficient of ~ 487 µV/K and were blended with a polymeric solution in different mass ratios to adjust the paste viscosity to the different requirements of 3D printing, electrospinning and low-pressure spray. The materials produced in every single stage of the paste synthesis were characterized by a variety of techniques that unequivocally prove their viability for producing thermoelectric parts and components. These can certainly trigger further research and development in green thermoelectric generators (TEGs) capable of adopting any form or shape with enhanced thermoelectric properties. These green TEGs are meant to compete with common toxic materials such as Bi₂Te₃, PbTe and CoSb that have Seebeck coefficients in the range of ~ 290–700 μV/K, similar to that of the produced Mg₂Si powders and lower than that of 3D printed bulk Mg₂Si pieces, measured to be ~ 4866 μV/K. Also, their measured thermal conductivities proved to be significantly lower (~ 0.2 W/mK) than that reported for Mg₂Si (≥ 4 W/mK). However, it is herein demonstrated that such thermoelectric properties are not stable over time. Pressureless sintering proved to be indispensable, but difficultly achievable by long thermal annealing (even above 32 h) in inert atmosphere at 400 °C, at least for bulk Mg₂Si pieces constituted by a mean grain size of 2–3 μm. Hence, for overcoming this sintering challenge and become the silicide’s extrusion viable in the production of bulk thermoelectric parts, alternative pressureless sintering methods will have to be further explored.

中文翻译：

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用于3D打印，静电纺丝和低压喷涂的热电硅化镁糊剂的合成。

在这项工作中，通过3D打印，喷涂和静电纺丝技术首次合成并测试了环保型硅化镁（Mg ₂ Si）半导体（n型）热电浆料，用于建筑与能源收集设备相关的组件。通过在Ar气氛下球磨和热退火相结合获得Mg ₂ Si细粉。尽管后一种工艺对于获得所需的Mg ₂ Si相至关重要，但球磨对于均匀化和减小粉末的粒度必不可少。合成镁₂硅粉的塞贝克系数很大，约为487 µV / K，并以不同的质量比与聚合物溶液混合，以调节浆料的粘度，以满足3D打印，静电纺丝和低压喷涂的不同要求。在糊剂合成的每个单一阶段中生产的材料，都通过各种技术来表征，这些技术明确证明了它们在生产热电零件和组件中的可行性。这些无疑可以引发对绿色热电发生器（TEG）的进一步研究和开发，这些热电发生器可以采用具有增强的热电特性的任何形式或形状。这些绿色TEG旨在与常见的有毒材料竞争，例如Bi ₂ Te ₃，PbTe和CoSb的塞贝克系数在〜290–700μV/ K的范围内，与生产的Mg ₂ Si粉末相似，但低于3D打印的块状Mg ₂ Si粉末，测量值为〜4866μV/ K. 同样，他们的测量的热导率被证明比Mg ₂ Si的报告的（> 4 W / mK）要低得多（〜0.2 W / mK）。然而，本文证明了这样的热电性质随时间不稳定。事实证明，无压烧结是必不可少的，但至少在大块Mg _2上，在惰性气氛中于400°C进行长时间的热退火（甚至超过32 h）很难实现，Si片的平均晶粒尺寸为2–3μm。因此，为了克服这种烧结挑战并成为在批量热电零件生产中硅化物的挤出可行的方法，必须进一步探索替代的无压烧结方法。