## 3 Results and Discussion
### Crystal Structure Analysis, PXRD Patterns, and SEM-EDS Analyses
\begin{table}
\begin{tabular}{c c} \hline \hline  & **CuCr\({}_{1-1}\)Sn\({}_{0.9}\)S\({}_{2.3}\)Se\({}_{1.7}\)**\$ \\ \hline Crystal system, space group & Crystal data \\ \(a\) (Å) & Cubic, \(Fd\overline{3}m\) \\ \(V\) (Å\({}^{3}\)) & 10.3578 (15) \\ \(\mu\) (mm\({}^{-1}\)) & 1111.2 (5) \\ Crystal size (mm) & 21.844 \\  & 0.25 \(\times\) 0.23 \(\times\) 0.21 \\  & Data collection \\ \(T_{\rm min}\), \(T_{\rm min}\) & 0.3119, 0.7485 \\ No. of measurements & 1152 \\ \(R_{\rm int}\), \(R_{\sigma}\) & 0.042, 0.039 \\ No. of independent reflections & 120 \\ (\(\sin\theta\)/\(\lambda\))\({}_{\rm max}\) (Å\({}^{-1}\)) & 0.747 \\  & Refinement \\ Refinement method & Full-matrix least-squares on \(F^{2}\) \\ No. of reflections & 111 \\ No. of parameters & 10 \\ Completeness to \(\theta\) = 25.242\({}^{\circ}\) & 97.6\% \\ \(R_{1}\)[\(F^{2}>2\sigma(F^{2})\)], \(R_{1}\) & 0.0249, 0.0266 \\ \(wR_{2}\)(\(F^{2}\)), \(wR_{2}\) & 0.0543, 0.0519 \\ Goodness-of-fit & 0.990 \\ Extinction coefficient & 0.0031 (3) \\ \(\Delta\rho_{\rm max}\), \(\Delta\rho_{\rm min}\) (e Å\({}^{-3}\)) & 1.32, \(-\)0.71 \\ \hline \hline \end{tabular} \({}^{\lx@sectionsign}\) Further details of the crystal structure investigation can be obtained from the crystallographic data with deposition number CSD 2124213. The crystallographic data can be obtained free of charge from the Cambridge Crystallographic Data Centre via [[http://www.ccdc.cam.ac.uk/data_request/cif](http://www.ccdc.cam.ac.uk/data_request/cif)]([http://www.ccdc.cam.ac.uk/data_request/cif](http://www.ccdc.cam.ac.uk/data_request/cif)).  
\end{table} 
Table 1: Crystallographic data and structure refinement details. Figure 2 show the PXRD patterns of the polycrystalline materials. The sharpness of the signals indicates high crystallinity, whereas the observed interlayer spacing is in good concordance with the interplanar spacing d calculated. The entire PXRD patterns obtained for these phases were indexed to the Fd\(\overline{3}\)m space group (spinel-type structure), confirming that the powder samples crystallized in a normal spinel-type structure. Rietveld refinements were performed using the PXRD data collected at RT temperature (Figure S1--see Supplementary Materials). The structural model obtained was in good concordance with the model based on the single-crystal XRD data. The R-indices were  
Figure 1: SEM analysis: Representative EDS mapping images (powder sample) and backscattered electron image of Cu\({}_{1\text{-}0}\)Cr\({}_{1\text{-}0}\)Sn\({}_{1\text{-}0}\)S\({}_{1\text{-}7}\)Se\({}_{2\text{-}3}\) (20 kV, 670\(\times\)). refined to reasonable values (Table 2). The Rietveld analysis refinement performed in the CuCr\({}_{1\cdot 6}\)Sn\({}_{0\cdot 4}\)S\({}_{2\cdot 3}\)Se\({}_{1\cdot 7}\) sample indicated the presence of minor phase impurities. The cell lattice parameters gradually increased with increasing Sn concentration (x), which concords with [PERSON]'s law (Figure S2). The chemical composition of the Rietveld analysis was in accordance with the nominal compositions. As expected, CuCr\({}_{2\cdot 3}\)Sn\({}_{3\cdot 2}\)S\({}_{1\cdot 7}\) and CuCr\({}_{2\cdot 3}\)Sn\({}_{3\cdot 1}\)\(\cdot\)S\({}_{2\cdot 3}\) cell parameter phases expanded owing to the substitution of Cr [Cr\({}^{3+}\)/Cr\({}^{4+}\)] by the larger Sn\({}^{4+}\) cation. The effective octahedral ionic radii of the Cr\({}^{3+}\), Cr\({}^{4+}\), and Sn\({}^{4+}\) cations published by [PERSON] are 0.62 A, 0.55 A, and 0.69 A, respectively. The cell parameter of CuCr\({}_{1\cdot 0}\)Sn\({}_{1\cdot 0}\)S\({}_{1\cdot 7}\)Se\({}_{2\cdot 3}\) was larger than that of CuCr\({}_{1\cdot 0}\)Sn\({}_{1\cdot 0}\)S\({}_{1\cdot 7}\)Se\({}_{2\cdot 3}\)Se\({}_{1\cdot 7}\) because of the substitution of S by the larger Se anions.