Witteveen Catherine, Górnicka Karolina, Chang Johan, Månsson Martin, Klimczuk Tomasz, von Rohr Fabian O
Department of Chemistry, University of Zürich, Winterthurerstr. 190, 8057 Zürich, Switzerland.
Department of Solid State Physics, Gdansk University of Technology, 80-233 Gdansk, Poland and Advanced Materials Centre, Gdansk University of Technology, ul. Narutowicza 11/12, 80-233 Gdansk, Poland.
Dalton Trans. 2021 Mar 9;50(9):3216-3223. doi: 10.1039/d0dt03636f.
We report on the phase formation and the superconducting properties in the NbS2 system. Specifically, we have performed a series of standardized solid-state syntheses in this system, which allow us to establish a comprehensive synthesis map for the formation of the two polytypes 2H-NbS2 and 3R-NbS2, respectively. We show that the identification of two polytypes by means of X-ray diffraction is not always unambiguous. Our physical property measurements on a phase-pure sample of 3R-NbS2, on a phase-pure sample of 2H-NbS2, and a mixed phase sample confirm earlier reports that 2H-NbS2 is a bulk superconductor and that 3R-NbS2 is not a superconductor above T = 1.75 K. Our results clearly show that specific heat measurements, as true bulk measurements, are crucial for the identification of superconducting materials in this and related systems. Our results indicate that for the investigation of van der Waals materials great care has to be taken on choosing the synthesis conditions for obtaining phase pure samples.
我们报告了NbS₂体系中的相形成和超导特性。具体而言，我们在该体系中进行了一系列标准化的固态合成，这使我们能够分别为两种多型体2H-NbS₂和3R-NbS₂的形成建立一个全面的合成图谱。我们表明，通过X射线衍射鉴定两种多型体并不总是明确的。我们对3R-NbS₂的纯相样品、2H-NbS₂的纯相样品以及混合相样品进行的物理性质测量证实了早期的报道，即2H-NbS₂是体超导体，而3R-NbS₂在T = 1.75 K以上不是超导体。我们的结果清楚地表明，作为真正的体测量，比热测量对于鉴定该体系及相关体系中的超导材料至关重要。我们的结果表明，对于范德华材料的研究，在选择合成条件以获得纯相样品时必须格外小心。
