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All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on Sr(ZnAs)2 by Materials Project

Sr(ZnAs)2 crystallizes in the trigonal P-3m1 space group. The structure is three-dimensional. Sr2+ is bonded to six equivalent As3- atoms to form SrAs6 octahedra that share corners with twelve equivalent ZnAs4 tetrahedra, edges with six equivalent SrAs6 octahedra, and edges with six equivalent ZnAs4 tetrahedra. All Sr–As bond lengths are 3.16 Å. Zn2+ is bonded to four equivalent As3- atoms to form ZnAs4 tetrahedra that share corners with six equivalent SrAs6 octahedra, corners with six equivalent ZnAs4 tetrahedra, edges with three equivalent SrAs6 octahedra, and edges with three equivalent ZnAs4 tetrahedra. The corner-sharing octahedra tilt angles range from 22–51°. There are three shorter (2.57 Å) and one longer (2.63 Å) Zn–As bond lengths. As3- is bonded to three equivalent Sr2+ and four equivalent Zn2+ atoms to form a mixture of distorted corner and edge-sharing AsSr3Zn4 pentagonal bipyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on La(ZnAs)3 by Materials Project

La(ZnAs)3 crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. La3+ is bonded to seven As3- atoms to form distorted LaAs7 pentagonal bipyramids that share corners with thirteen ZnAs4 tetrahedra, edges with two equivalent LaAs7 pentagonal bipyramids, edges with seven ZnAs4 tetrahedra, and faces with two equivalent LaAs7 pentagonal bipyramids. There are a spread of La–As bond distances ranging from 3.06–3.23 Å. There are three inequivalent Zn2+ sites. In the first Zn2+ site, Zn2+ is bonded to four As3- atoms to form ZnAs4 tetrahedra that share corners with four equivalent LaAs7 pentagonal bipyramids, corners with nine ZnAs4 tetrahedra, edges with three equivalent LaAs7 pentagonal bipyramids, and an edgeedge with one ZnAs4 tetrahedra. There are a spread of Zn–As bond distances ranging from 2.52–2.58 Å. In the second Zn2+ site, Zn2+ is bonded to four As3- atoms to form ZnAs4 tetrahedra that share corners with three equivalent LaAs7 pentagonal bipyramids, corners with eight ZnAs4 tetrahedra, edges with three equivalent LaAs7 pentagonal bipyramids, and edges with two equivalent ZnAs4 tetrahedra. There are a spread of Zn–As bond distances ranging from 2.49–2.80 Å. In the third Zn2+ site, Zn2+ is bonded to four As3- atoms to form ZnAs4 tetrahedra that share corners with six equivalent LaAs7 pentagonal bipyramids, corners with five ZnAs4 tetrahedra, an edgeedge with one LaAs7 pentagonal bipyramid, and edges with five ZnAs4 tetrahedra. There are three shorter (2.58 Å) and one longer (2.63 Å) Zn–As bond lengths. There are three inequivalent As3- sites. In the first As3- site, As3- is bonded in a 7-coordinate geometry to two equivalent La3+ and five Zn2+ atoms. In the second As3- site, As3- is bonded in a 6-coordinate geometry to two equivalent La3+ and four Zn2+ atoms. In the third As3- site, As3- is bonded to three equivalent La3+ and three Zn2+ atoms to form distorted edge-sharing AsLa3Zn3 octahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Eu(ZnAs)2 by Materials Project

Eu(ZnAs)2 crystallizes in the trigonal P-3m1 space group. The structure is three-dimensional. Eu2+ is bonded to six equivalent As3- atoms to form EuAs6 octahedra that share corners with twelve equivalent ZnAs4 tetrahedra, edges with six equivalent EuAs6 octahedra, and edges with six equivalent ZnAs4 tetrahedra. All Eu–As bond lengths are 3.09 Å. Zn2+ is bonded to four equivalent As3- atoms to form ZnAs4 tetrahedra that share corners with six equivalent EuAs6 octahedra, corners with six equivalent ZnAs4 tetrahedra, edges with three equivalent EuAs6 octahedra, and edges with three equivalent ZnAs4 tetrahedra. The corner-sharing octahedra tilt angles range from 21–53°. There are three shorter (2.56 Å) and one longer (2.62 Å) Zn–As bond lengths. As3- is bonded to three equivalent Eu2+ and four equivalent Zn2+ atoms to form a mixture of distorted edge and corner-sharing AsEu3Zn4 pentagonal bipyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Yb(ZnAs)2 by Materials Project

YbZn2As2 crystallizes in the trigonal P-3m1 space group. The structure is three-dimensional. Yb2+ is bonded to six equivalent As3- atoms to form YbAs6 octahedra that share corners with twelve equivalent ZnAs4 tetrahedra, edges with six equivalent YbAs6 octahedra, and edges with six equivalent ZnAs4 tetrahedra. All Yb–As bond lengths are 3.00 Å. Zn2+ is bonded to four equivalent As3- atoms to form ZnAs4 tetrahedra that share corners with six equivalent YbAs6 octahedra, corners with six equivalent ZnAs4 tetrahedra, edges with three equivalent YbAs6 octahedra, and edges with three equivalent ZnAs4 tetrahedra. The corner-sharing octahedra tilt angles range from 18–54°. There are three shorter (2.54 Å) and one longer (2.64 Å) Zn–As bond lengths. As3- is bonded to three equivalent Yb2+ and four equivalent Zn2+ atoms to form a mixture of distorted edge and corner-sharing AsYb3Zn4 pentagonal bipyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ba(ZnAs)2 by Materials Project

BaZn2As2 is alpha bismuth trifluoride-derived structured and crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Ba2+ is bonded in a body-centered cubic geometry to eight equivalent As3- atoms. All Ba–As bond lengths are 3.48 Å. Zn2+ is bonded to four equivalent As3- atoms to form a mixture of edge and corner-sharing ZnAs4 tetrahedra. All Zn–As bond lengths are 2.60 Å. As3- is bonded in a 8-coordinate geometry to four equivalent Ba2+ and four equivalent Zn2+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on ZnAs by Materials Project

AsZn is SC16 CuCl, stable at 5GPa structured and crystallizes in the orthorhombic Pbca space group. The structure is three-dimensional. Zn2+ is bonded to four equivalent As2- atoms to form a mixture of edge and corner-sharing ZnAs4 tetrahedra. There are a spread of Zn–As bond distances ranging from 2.50–2.72 Å. As2- is bonded in a 5-coordinate geometry to four equivalent Zn2+ and one As2- atom. The As–As bond length is 2.46 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ba(ZnAs)2 by Materials Project

BaZn2As2 crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. Ba2+ is bonded in a 7-coordinate geometry to seven As3- atoms. There are a spread of Ba–As bond distances ranging from 3.32–3.63 Å. There are two inequivalent Zn2+ sites. In the first Zn2+ site, Zn2+ is bonded to four As3- atoms to form a mixture of edge and corner-sharing ZnAs4 tetrahedra. There are a spread of Zn–As bond distances ranging from 2.56–2.61 Å. In the second Zn2+ site, Zn2+ is bonded to four As3- atoms to form a mixture of edge and corner-sharing ZnAs4 tetrahedra. There are a spread of Zn–As bond distances ranging from 2.53–2.65 Å. There are two inequivalent As3- sites. In the first As3- site, As3- is bonded in a 7-coordinate geometry to three equivalent Ba2+ and four Zn2+ atoms. In the second As3- site, As3- is bonded in a 4-coordinate geometry to four equivalent Ba2+ and four Zn2+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ca(ZnAs)2 by Materials Project

CaZn2As2 crystallizes in the trigonal P-3m1 space group. The structure is three-dimensional. Ca2+ is bonded to six equivalent As3- atoms to form CaAs6 octahedra that share corners with twelve equivalent ZnAs4 tetrahedra, edges with six equivalent CaAs6 octahedra, and edges with six equivalent ZnAs4 tetrahedra. All Ca–As bond lengths are 3.03 Å. Zn2+ is bonded to four equivalent As3- atoms to form ZnAs4 tetrahedra that share corners with six equivalent CaAs6 octahedra, corners with six equivalent ZnAs4 tetrahedra, edges with three equivalent CaAs6 octahedra, and edges with three equivalent ZnAs4 tetrahedra. The corner-sharing octahedra tilt angles range from 19–53°. There are three shorter (2.55 Å) and one longer (2.63 Å) Zn–As bond lengths. As3- is bonded to three equivalent Ca2+ and four equivalent Zn2+ atoms to form a mixture of distorted edge and corner-sharing AsCa3Zn4 pentagonal bipyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2022

On the Effects of Aliovalent Substitutions in Thermoelectric Zintl Pnictides. Varied Polyanionic Dimensionality and Complex Structural Transformations–The Case of Sr 3 ZnP 3 vs Sr 3 Al x Zn 1– x P 3

The structures and the transport properties of a novel family of Zintl phosphides and arsenides with the formula AE 3 ZnPn 3 and the solid solutions AE 3 Al x Zn 1–x Pn 3 , AE 3 ZnAs y P 1–y (AE = Sr, Eu; Pn = P, As) are reported. Crystals of nine new phases have been obtained via Pb-flux reactions and used for structural work by means of single-crystal X-ray diffraction methods. The derived orthorhombic structure is without a direct analog, and features unusual structural units, where the Zn atoms are in both distorted tetrahedral and trigonal-planar coordination of pnictogens. Electronic structure calculations reveal moderately wide bandgaps for Sr 3 ZnP 3 and Sr 3 ZnAs 3 , on the order of 0.70 and 0.63 eV, respectively. Electrical transport measurements above room temperature indicate relatively high resistivity values above 500 K (ρ ≈ 4.8 Ω cm and above), but some of the samples exhibit very high Seebeck coefficients, as large as 300 μV/K at 560 K for Sr 3 ZnAs 3 . Aliovalent substitutions in AE 3 ZnPn 3 , achieved by the partial replacement of Zn 2+ with Al 3+ cations promote occupational and positional disorder, which causes structural transformation towards the disordered variant of the Sr 5 Al 2 Sb 6 structure type. Such substitutions also change the dimensionality of the polyanionic sub-lattice in the resulting quaternary AE 3 Al x Zn 1–x Pn 3 phases. Furthermore, preliminary transport property data on the latter reveal nine times lower electrical resistivity (ρ 500 ≈ 0.5 Ω cm) together with a significantly enhanced Seebeck coefficient, αmax ≈ 430 μV/K at 560 K.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Advancing Heteroanionicity in Zintl Phases: Crystal Structures, Thermoelectric and Magnetic Properties of Two Quaternary Semiconducting Arsenide Oxides, Eu 8 Zn 2 As 6 O and Eu 14 Zn 5 As 12 O

Two novel quaternary oxyarsenides, Eu 8 Zn 2 As 6 O and Eu 14 Zn 5 As 12 O, were synthesized through metal flux reactions, and their crystal structures were established by single-crystal X-ray diffraction methods. Eu 8 Zn 2 As 6 O crystallizes in the orthorhombic space group Pbca, featuring polyanionic ribbons composed of corner-shared triangular [ZnAs 3 ] units, running along the [100] direction. The structure of Eu 14 Zn 5 As 12 O crystallizes in the monoclinic space group P2/m and its anionic substructure can be described as an infinite “ribbonlike” chain comprised of [ZnAs 3 ] trigonal-planar units, although the structural complexity here is greater and also amplified by disorder on multiple crystallographic positions. In both structures, the O 2– anion occupies an octahedral void with six neighboring Eu 2+ cations. Formal electron counting, electronic structure calculations, and transport properties reveal the charge-balanced semiconducting nature of these heteroanionic Zintl phases. High-temperature thermoelectric transport properties measurements on Eu 14 Zn 5 As 12 O reveal relatively high resistivity (ρ 500K = 8 Ω·cm) and Seebeck coefficient values (S 500K = 220 μV K –1 ), along with a low concentration and mobility of holes as the dominant charge-carriers (n 500K = 8.0 × 10 17 cm –3 , μ 500K = 6.4 cm 2 /V s). Magnetic studies indicate the presence of divalent Eu 2+ species in Eu 14 Zn 5 As 12 O and complex magnetic ordering, with two transitions observed at T 1 = 21.6 K and T 2 = 9 K.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗