Bottom-up solution synthesis has been considered as a facile and energy-efficient approach for SnSe thermoelectric materials. Herein, we report a microwave-assisted hydrothermal method for the fast and controllable synthesis of SnSe with optimised thermoelectric properties. The NaOH concentration in solution precursors was demonstrated as a key factor influencing the phase composition, diameter, and morphology of the hydrothermal products as well as the thermoelectric properties of the corresponding sintered pellets. It is found that a NaOH : SnCl₂ molar ratio of 30 leads to the formation of phase-pure SnSe microrods, and the pellet constructed from these rods obtains a maximum ZT of 1.08 and 0.78 at 773 K in parallel and perpendicular alignments to the pressing direction, respectively. These ZT values are significantly higher than the ZT value achieved by the pellet that was sintered from the hydrothermal powders prepared without NaOH and comprised the mixed phases of SnSe, SnO₂, and SnSe₂. This enhancement is primarily due to the improved power factor together with the lower lattice thermal conductivity owing to the significantly reduced fraction of SnO₂ in the pellet. This study not only provides a microwave-assisted solution strategy for the fast, efficient, and controllable synthesis of SnSe materials, but also identifies the key synthesis parameters for securing better thermoelectric performance.

中文翻译：

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微波辅助水热合成SnSe：杂质去除和增强的热电性能

自下而上的溶液合成已被认为是SnSe热电材料的一种简便且节能的方法。本文中，我们报道了一种微波辅助水热法，用于快速和可控地合成具有优化热电性能的SnSe。溶液前体中的NaOH浓度被证明是影响水热产物的相组成，直径和形态以及相应的烧结球团的热电性能的关键因素。发现NaOH：SnCl _2的摩尔比为30导致形成纯相SnSe微棒，并且由这些棒构成的颗粒获得最大的ZT分别在773 K处与压制方向平行和垂直对齐时的1.08和0.78。这些ZT值显着高于由不使用NaOH制备的水热粉末烧结而成的颗粒的ZT值，该水热粉末包含SnSe，SnO ₂和SnSe ₂的混合相。这种增强主要归因于功率因数的提高以及由于SnO ₂分数的显着降低而降低了晶格热导率在颗粒中。这项研究不仅为快速，高效和可控制的SnSe材料合成提供了微波辅助的解决方案，而且还确定了确保更好的热电性能的关键合成参数。