Castillo-Hernández Gustavo, Müller Eckhard, de Boor Johannes
Institute of Materials Research, German Aerospace Center, 51170 Cologne, Germany.
Institute of Inorganic and Analytical Chemistry, Justus Liebig University Giessen, Heinrich-Buff-Ring 17, 35392 Giessen, Germany.
Materials (Basel). 2022 Jan 20;15(3):779. doi: 10.3390/ma15030779.
Thermoelectric generators are an excellent option for waste heat reuse. Materials for such devices have seen their thermoelectric properties improving constantly. The functioning of a generator, however, does not only depend on thermoelectric properties. Thermal and mechanical properties play a decisive role in the feasibility of any thermoelectric generator. To shed light on the properties exhibited by thermoelectric materials, we present the temperature dependent characterization of Young's modulus and coefficient of thermal expansion for MgSiSn. Comparing undoped to Bi-doped n-type and Li-doped p-type material, we investigated the influence of doping in the relevant temperature regime and found the influences to be minor, proving similar properties for n- and p-type. We found a Young's modulus of 84 GPa for the p-type and 83 GPa for the n-type, similar to that of the undoped compound with 85 GPa. The thermal expansion coefficients of undoped, as well as n- and p-type were equally similar with values ranging from 16.5 to 17.5 × 10 1/K. A phase analysis was performed to further compare the two materials, finding a similar phase distribution and microstructure. Finally, using the gathered data, estimations on the possible thermally induced stresses under a temperature difference are provided to evaluate the relevance of knowing temperature dependent thermal and mechanical properties.
热电发电机是废热再利用的绝佳选择。此类设备的材料的热电性能一直在不断提高。然而，发电机的运行不仅取决于热电性能。热性能和机械性能对任何热电发电机的可行性起着决定性作用。为了阐明热电材料所表现出的性能，我们展示了MgSiSn的杨氏模量和热膨胀系数随温度的变化特征。通过比较未掺杂的材料与Bi掺杂的n型材料以及Li掺杂的p型材料，我们研究了在相关温度范围内掺杂的影响，发现影响较小，这证明n型和p型材料具有相似的性能。我们发现p型材料的杨氏模量为84 GPa，n型材料为83 GPa，与未掺杂化合物的85 GPa相似。未掺杂的以及n型和p型材料的热膨胀系数同样相似，数值范围为16.5至17.5×10⁻⁶ 1/K。进行了相分析以进一步比较这两种材料，发现它们具有相似的相分布和微观结构。最后，利用收集到的数据，对温差下可能产生的热致应力进行了估算，以评估了解随温度变化的热性能和机械性能的相关性。
