Rerefinement of the crystal structure of SnTe0.73(2)Se0.27(2) from single-crystal X-ray diffraction data

Moris, S.; Galdámez, A.

doi:10.1107/S2414314622007295

inorganic compounds

IUCrDATA

ISSN: 2414-3146

Volume 7| Part 7| July 2022| x220729

https://doi.org/10.1107/S2414314622007295

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Rerefinement of the crystal structure of SnTe_0.73(2)Se_0.27(2) from single-crystal X-ray diffraction data

Silvana Moris ^a and Antonio Galdámez ^b ^*

^aCentro de Investigación de Estudios Avanzados del Maule (CIEAM), Vicerrectoría de Investigación y Postgrado, Universidad Católica del Maule, Avenida San Miguel 3605, Talca 3480112, Chile, and ^bUniversidad de Chile, Facultad de Ciencias, Departamento de Química, Casilla 653, Santiago, Chile
^*Correspondence e-mail: agaldamez@uchile.cl

Edited by M. Weil, Vienna University of Technology, Austria (Received 29 June 2022; accepted 14 July 2022; online 19 July 2022)

Compounds of the solid solution series SnTe_1–xSe_x, derived from pristine SnSe and SnTe, are considered as thermoelectric lead-free materials. The crystal structure re-refinement of NaCl-type SnTe_0.73 (2)Se_0.27 (2) is based on single-crystal X-ray diffraction data and results in higher precision of the bond length [Sn—(Te,Se) = 3.0798 (3) Å] compared to a previous report on basis of powder X-ray data [Krebs & Langner (1964 ). Z. Anorg. Allg. Chem. 334, 37–49].

Keywords: single-crystal; solid solution; rerefinement; tin chalcogenide.

CCDC reference: 2190397

Structure description

Lead chalcogenides have proven to exhibit an excellent performance as thermoelectric materials. However, due to the current environmental regulations, generating lead-free materials with thermoelectric properties becomes necessary. In this regard, semiconductors of the solid-solution series SnTe_1–xSe_x have the potential to be good lead-free thermoelectric materials at mid/high temperatures (Banik & Biswas, 2014 ). Characterization of phases in the SnTe_1–xSe_x system on the basis of powder X-ray diffraction data has been reported previously (Krebs & Langner, 1964; Totani et al., 1968 ; Liu & Chang, 1992 ; Ariponnammacl et al., 1996 ; Majid & Legendre, 1998 ; Banik & Biswas, 2014). The powder patterns were indexed in the cubic crystal system, revealing an NaCl-type crystal structure. The reported unit-cell parameters (Liu & Chang, 1992) of SnTe_0.9Se_0.1 and SnTe_0.75Se_0.25 are a = 6.2433 Å and a = 6.2188 Å, respectively. The SnTe_1–xSe_x (x = 0 to 0.15) samples could be viewed as solid solutions that obey Vegard's law (Banik & Biswas, 2014). The parameter a of the cubic unit cell increases from approximately 6.23 to 6.27 Å with decreasing Se content x, as determined from the powder pattern.

Here, we report the crystal structure rerefinement of the solid solution with composition SnTe_0.73 (2)Se_0.27 (2) from single-crystal X-ray diffraction data. The crystal structure of SnTe_0.73 (2)Se_0.27 (2) likewise adopts the NaCl type (Fig. 1) with an intermediate value of a [6.1595 (5) Å] between those of the binary compounds SnTe (6.314 Å) and SnSe (5.99 Å), which is attributed to the different radii of Te and Se. The cell parameter reported by Liu & Chang (1992) of a = 6.2188 Å for SnTe_0.75Se_0.25 at room temperature is somewhat higher than that of SnTe_0.73 (2)Se_0.27 (2) determined at 150 K. The present study allowed for a higher precision with respect to the bond lengths in SnTe_0.73 (2)Se_0.27 (2), which is Sn—(Te,Se) = 3.0798 (3) Å.

Figure 1
A view of the NaCl-type crystal structure of SnTe_0.73 (2)Se_0.27 (2). Displacement ellipsoids are drawn at the 50% probability level.

Synthesis and crystallization

Single crystals of the title compound were obtained serendipitously by application of the high-temperature ceramic method. Powders of silver (99.99%), tin (99.99%), bismuth (99.999%), selenium (99%) and tellurium (99%) were weighted in an molar ratio of 1:2:1:2.5:2.5. All manipulations were carried out under an argon atmosphere. The reaction mixture was sealed in an evacuated silica ampoule and placed in a programmable furnace (Figueroa-Millon et al., 2018 ). The ampoule was slowly heated from room temperature to 1023 K at a rate of 333 K min⁻¹ to the maximum temperature and held for 7 d, followed by slow cooling to room temperature at a rate of 278 K h⁻¹. The reaction product consisted of a gray metallic powder (yield ∼99%) accompanied by black octahedrally shaped single crystals (yield ∼1%) that were manually separated for the X-ray diffraction study. The refined composition of the measured crystal is SnTe_0.73 (2)Se_0.27 (2).

Refinement

Crystal data, data collection, and structure refinement details are summarized in Table 1. For the shared chalcogenide site, the sum of site occupation factors (SOF) was constrained to 1, and the anisotropic displacement parameters were constrained to be the same. The crystal under investigation consisted of two domains with approximately equal contribution to the intensity data. The integration procedure showed that the reflections of each domain were clearly separated. For the final intensity data only one domain was used.

Table 1
Experimental details

Crystal data
Chemical formula	SnTe_0.73Se_0.27
M_r	233.28
Crystal system, space group	Cubic, Fm $[\overline{3}]$ m
Temperature (K)	150
a (Å)	6.1595 (5)
V (Å³)	233.69 (6)
Z	4
Radiation type	Mo Kα
μ (mm⁻¹)	23.61
Crystal size (mm)	0.10 × 0.08 × 0.07

Data collection
Diffractometer	Nonius KappaCCD
Absorption correction	Multi-scan (SADABS; Krause et al., 2015 )
T_min, T_max	0.103, 0.205
No. of measured, independent and observed [I > 2σ(I)] reflections	396, 33, 33
R_int	0.042
(sin θ/λ)_max (Å⁻¹)	0.703

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.045, 0.115, 1.49
No. of reflections	33
No. of parameters	4
Δρ_max, Δρ_min (e Å⁻³)	1.92, −1.84
Computer programs: COLLECT (Bruker, 1997-2004 ), DIRAX/LSQ (Duisenberg et al., 2003 ), EVALCCD (Duisenberg et al., 2003), olex2.solve (Bourhis et al., 2015 ), SHELXL (Sheldrick, 2015 ), OLEX2 (Dolomanov et al., 2009 ) and publCIF (Westrip, 2010 ).

Structural data

CCDC reference: 2190397

Crystal structure: contains datablocks 1R, I. DOI: https://doi.org/10.1107/S2414314622007295/wm4169sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2414314622007295/wm4169Isup2.hkl

checkCIF report

Computing details top

Data collection: Collect (Bruker, 1997-2004); cell refinement: DIRAX/LSQ (Duisenberg et al., 2003); data reduction: EVALCCD (Duisenberg et al., 2003); program(s) used to solve structure: olex2.solve (Bourhis et al., 2015); program(s) used to refine structure: SHELXL (Sheldrick, 2015); molecular graphics: OLEX2 (Dolomanov et al., 2009); software used to prepare material for publication: publCIF (Westrip, 2010).

Tin tellurium selenide top

Crystal data top

SnTe_0.73Se_0.27	Mo Kα radiation, λ = 0.71073 Å
M_r = 233.28	Cell parameters from 553 reflections
Cubic, Fm3m	θ = 5.7–39.8°
a = 6.1595 (5) Å	µ = 23.61 mm⁻¹
V = 233.69 (6) Å³	T = 150 K
Z = 4	Octahedron, black
F(000) = 389	0.10 × 0.08 × 0.07 mm
D_x = 6.631 Mg m⁻³

Data collection top

Nonius KappaCCD diffractometer	33 independent reflections
Radiation source: Enraf Nonius FR590	33 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.042
Detector resolution: 9 pixels mm^-1	θ_max = 30.0°, θ_min = 5.7°
CCD rotation images, thin slices scans	h = −8→8
Absorption correction: multi-scan (SADABS; Krause et al., 2015)	k = −7→8
T_min = 0.103, T_max = 0.205	l = −6→8
396 measured reflections

Refinement top

Refinement on F²	4 parameters
Least-squares matrix: full	0 restraints
R[F² > 2σ(F²)] = 0.045	w = 1/[σ²(F_o²) + (0.0583P)² + 1.8772P] where P = (F_o² + 2F_c²)/3
wR(F²) = 0.115	(Δ/σ)_max < 0.001
S = 1.49	Δρ_max = 1.92 e Å⁻³
33 reflections	Δρ_min = −1.84 e Å⁻³

Special details top

Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq	Occ. (<1)
Sn	0.000000	0.000000	0.000000	0.0199 (10)
Te	0.000000	0.000000	0.500000	0.0330 (12)	0.73 (2)
Se	0.000000	0.000000	0.500000	0.0330 (12)	0.27 (2)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Sn	0.0199 (10)	0.0199 (10)	0.0199 (10)	0.000	0.000	0.000
Te	0.0330 (12)	0.0330 (12)	0.0330 (12)	0.000	0.000	0.000
Se	0.0330 (12)	0.0330 (12)	0.0330 (12)	0.000	0.000	0.000

Geometric parameters (Å, º) top

Sn—Teⁱ	3.0798 (3)	Sn—Teⁱⁱⁱ	3.0798 (3)
Sn—Te	3.0798 (3)	Sn—Te^iv	3.0798 (3)
Sn—Teⁱⁱ	3.0798 (3)	Sn—Te^v	3.0798 (3)

Teⁱ—Sn—Te	90.0	Sn^vi—Te—Sn	90.0
Teⁱ—Sn—Teⁱⁱ	90.0	Sn^vi—Te—Sn^vii	90.0
Te—Sn—Teⁱⁱ	180.0	Sn—Te—Sn^vii	180.0
Teⁱ—Sn—Teⁱⁱⁱ	90.0	Sn^vi—Te—Sn^viii	90.0
Te—Sn—Teⁱⁱⁱ	90.0	Sn—Te—Sn^viii	90.0
Teⁱⁱ—Sn—Teⁱⁱⁱ	90.0	Sn^vii—Te—Sn^viii	90.0
Teⁱ—Sn—Te^iv	90.0	Sn^vi—Te—Sn^ix	90.0
Te—Sn—Te^iv	90.0	Sn—Te—Sn^ix	90.0
Teⁱⁱ—Sn—Te^iv	90.0	Sn^vii—Te—Sn^ix	90.0
Teⁱⁱⁱ—Sn—Te^iv	180.0	Sn^viii—Te—Sn^ix	180.0
Teⁱ—Sn—Te^v	180.0	Sn^vi—Te—Sn^x	180.0
Te—Sn—Te^v	90.0	Sn—Te—Sn^x	90.0
Teⁱⁱ—Sn—Te^v	90.0	Sn^vii—Te—Sn^x	90.0
Teⁱⁱⁱ—Sn—Te^v	90.0	Sn^viii—Te—Sn^x	90.0
Te^iv—Sn—Te^v	90.0	Sn^ix—Te—Sn^x	90.0

Symmetry codes: (i) x+1/2, y, z−1/2; (ii) x, y, z−1; (iii) x, y−1/2, z−1/2; (iv) x, y+1/2, z−1/2; (v) x−1/2, y, z−1/2; (vi) x+1/2, y, z+1/2; (vii) x, y, z+1; (viii) x, y−1/2, z+1/2; (ix) x, y+1/2, z+1/2; (x) x−1/2, y, z+1/2.

Acknowledgements

The authors are grateful to Vincent Dorcet (Centre de Diffractométrie X CDIFX), Université de Rennes 1, France.

Funding information

This work was supported by FONDECYT grant No. 1190856.

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