The development of thermoelectrics for high-temperature applications imposes several essential requirements on the material properties. In some energy-conversion scenarios, the cost and thermal stability requirements may dominate over efficiency issues, making abundant, high-temperature-stable and low-toxic oxides attractive alternative thermoelectric materials. As compared to “traditional” thermoelectrics, oxides possess unique redox flexibility and defect chemistry, which can be precisely tuned by external temperature and oxygen partial pressure conditions. This work aims to demonstrate how, by redox-sensitive substitutions, the thermoelectric properties of oxides can be tuned and enhanced. The proposed strategy is exemplified by considering molybdenum-containing strontium titanate within nominally single-substituted and nanocomposite concepts. The involved materials design allows us to proceed from an in-depth understanding of the redox-promoted effects to the demonstration of the enhanced thermoelectric performance attained by redox engineering. Synergistic enhancement of the Seebeck coefficient and suppression of the thermal conductivity due to combined carrier filtering effects and efficient phonon scattering at redox-induced interfaces provided up to 25% increase in the thermoelectric performance. The results demonstrate extraordinary flexibility of the perovskite lattice towards retaining a rich combination of the molybdenum redox states and shifting their ratio by tuning the A-site stoichiometry, and the prospects for developing new materials combining thermoelectric and (electro)catalytic functionalities.

中文翻译：

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钛酸锶热电材料的氧化还原工程

用于高温应用的热电学的发展对材料性能提出了一些基本要求。在某些能量转换方案中，成本和热稳定性要求可能会超过效率问题，从而使大量的高温稳定且低毒的氧化物成为有吸引力的热电替代材料。与“传统”热电相比，氧化物具有独特的氧化还原柔韧性和缺陷化学性质，可以通过外部温度和氧气分压条件进行精确调节。这项工作旨在证明如何通过对氧化还原敏感的取代来调节和增强氧化物的热电性质。通过考虑名义上单取代和纳米复合概念中的含钼钛酸锶来举例说明该策略。所涉及的材料设计使我们能够从对氧化还原促进作用的深入了解开始，向人们展示氧化还原工程所获得的增强的热电性能。由于结合了载流子滤波效应和氧化还原诱导的界面上的有效声子散射，塞贝克系数得到了协同增强，导热系数得到了抑制，从而使热电性能提高了25％。结果表明，钙钛矿晶格具有极大的灵活性，可以保持钼氧化还原态的丰富组合并通过调整A位化学计量来改变它们的比率，并具有开发结合热电和（电）催化功能的新材料的前景。