Institut für Anorganische Chemie und Analytische Chemie der Johannes Gutenberg-Universität, Duesbergweg 10-14, D-55099 Mainz, Germany.
Department of Materials Science and Engineering, Northwestern University, 2220 Campus Drive, Evanston, IL 60208, USA.
Dalton Trans. 2019 Nov 14;48(42):15822-15829. doi: 10.1039/c9dt03247a. Epub 2019 Oct 2.
Inspired by the good performance of argyrodites as ion conducting thermoelectrics and as solid electrolytes we investigated the effect of isovalent S substitution for Se in CuPSe. At room temperature CuPSe crystallizes in the primitive cubic β-polymorph of the argyrodite structure and transforms to the face-centered high-temperature (HT) γ-modification above 320 K. The transition for the homologous CuPS occurs at 510 K. Promising thermoelectric and ion conducting properties are observed only in the HT modification, where the cations are mobile. Using Rietveld refinements against X-ray diffraction data the effect of isovalent S substitution for Se on the structural and transport properties in CuPSeS was analyzed. While a step-wise incorporation of S showed typical behavior for a homogeneous solid solution series, the analysis of the diffraction data gave clear evidence of anion ordering due to site preference of the sulfide ions, which can be rationalized using Pearson's HSAB concept. This leads to a stabilization of the HT structure even at lower temperatures. This selective control enables new strategies for the design of argyrodite materials, as isovalent substitution not only allows an engineering of properties, but also permits the stabilization of the polymorph with the most promising properties.
受银辉矿作为离子导电的热电体和固体电解质的优异性能的启发，我们研究了等电子 S 取代 CuPSe 中的 Se 的影响。在室温下，CuPSe 结晶为银辉矿结构的原始立方β多晶型，并在 320 K 以上转变为面心立方高温（HT）γ修饰。同系物 CuPS 的转变发生在 510 K。只有在 HT 修饰中才观察到有前途的热电和离子导电性能，因为在 HT 修饰中，阳离子是可移动的。利用 X 射线衍射数据的 Rietveld 精修分析了等电子 S 取代 Se 对 CuPSeS 的结构和输运性质的影响。虽然 S 的逐步掺入表现出同成分固溶体系列的典型行为，但衍射数据的分析清楚地表明了阴离子有序，这是由于硫离子的位偏好，可以用 Pearson 的 HSAB 概念来合理化。这导致 HT 结构即使在较低温度下也能稳定。这种选择性控制为银辉矿材料的设计提供了新的策略，因为等电子取代不仅允许对性能进行工程设计，而且还允许对具有最有前途性能的多晶型进行稳定。
