Enhancement of thermoelectric properties of CuFeS 2 through formation of spinel-type microprecipitates
Enhancement of thermoelectric properties of CuFeS 2 through formation of spinel-type microprecipitates
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通过形成尖晶石型微沉淀物增强 CuFeS 2 的热电性能
DOI：
10.1039/d3ta05011d
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发表时间：
2023
影响因子：
11.9
通讯作者：
Tippireddy S
中科院分区：
文献类型：
--
作者：
Tippireddy S
CuFeS2（黄铜矿）是一种很有前景的 n 型热电候选材料，可用于低品位废热回收。在这项工作中，通过固相合成制备了通式为 Cu1−xCrxFeS2 (0.0 ≤ x ≤ 0.1) 的含铬 CuFeS2 材料。在 CuFeS2 中取代铬的努力导致了复合材料的优先形成，其中富含 Cr 的尖晶石型 [Cu,Fe,Cr]3S4 相的层状沉淀物嵌入未取代的 CuFeS2 基体中。 X 射线吸收近边光谱 (XANES) 表明，CuFeS2 主相中铜、铁和硫的电子结构并未因铬的掺入而改变。然而，[Cu,Fe,Cr]3S4 沉淀的形成改变了 CuFeS2 相的 Cu : Fe 比率，通过部分 Fe3+ 离子还原为 Fe2+ 产生净载流子浓度的变化。尖晶石析出物的铬含量决定了主CuFeS2相的Cu : Fe比的变化程度，从而间接影响电性能。微米/纳米尺寸的[Cu,Fe,Cr]3S4 沉淀物和纳米级位错使得广谱的载热声声子被散射，从而导致晶格热导率显着降低。结合增强的功率因数，x = 0.08 样品在 673 K 时实现了 0.31 的最大热电品质因数 zT；比原始阶段增加了三倍。
CuFeS2 (chalcopyrite) is a promising n-type thermoelectric candidate for low-grade waste heat recovery. In this work, chromium-containing CuFeS2 materials of general formula Cu1−xCrxFeS2 (0.0 ≤ x ≤ 0.1) were prepared via solid-state synthesis. Efforts to substitute chromium in CuFeS2 leads to the preferential formation of a composite, in which lamellar precipitates of a Cr-rich, spinel-type [Cu,Fe,Cr]3S4 phase, are embedded in the unsubstituted CuFeS2 matrix. X-ray absorption near-edge spectroscopy (XANES) reveals that the electronic structure of copper, iron and sulfur in the principal CuFeS2 phase remains unaltered by chromium incorporation. However, the formation of [Cu,Fe,Cr]3S4 precipitates alters the Cu : Fe ratio of the CuFeS2 phase, producing a change in the net carrier concentration through reduction of a portion of Fe3+ ions to Fe2+. The chromium content of the spinel precipitates determines the extent of the change in the Cu : Fe ratio of the main CuFeS2 phase, and hence, indirectly affects the electrical properties. The micro/nanometre-sized [Cu,Fe,Cr]3S4 precipitates and nanoscale dislocations enable a broad spectrum of heat-carrying acoustic phonons to be scattered, resulting in a significantly reduced lattice thermal conductivity. Combined with an enhanced power factor, a maximum thermoelectric figure-of-merit, zT of 0.31 at 673 K is achieved for the x = 0.08 sample; a three-fold increase over that of the pristine phase.