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12 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on NiSbS by Materials Project

NiSbS is Hausmannite-derived structured and crystallizes in the cubic P2_13 space group. The structure is three-dimensional. Ni3+ is bonded to three equivalent Sb1- and three equivalent S2- atoms to form distorted NiSb3S3 octahedra that share corners with twelve equivalent NiSb3S3 octahedra, corners with three equivalent SbNi3S trigonal pyramids, and corners with three equivalent SNi3Sb trigonal pyramids. The corner-sharing octahedral tilt angles are 63°. All Ni–Sb bond lengths are 2.56 Å. All Ni–S bond lengths are 2.37 Å. Sb1- is bonded to three equivalent Ni3+ and one S2- atom to form distorted SbNi3S trigonal pyramids that share corners with three equivalent NiSb3S3 octahedra, corners with six equivalent SbNi3S trigonal pyramids, and corners with nine equivalent SNi3Sb trigonal pyramids. The corner-sharing octahedral tilt angles are 80°. The Sb–S bond length is 2.57 Å. S2- is bonded to three equivalent Ni3+ and one Sb1- atom to form distorted SNi3Sb trigonal pyramids that share corners with three equivalent NiSb3S3 octahedra, corners with six equivalent SNi3Sb trigonal pyramids, and corners with nine equivalent SbNi3S trigonal pyramids. The corner-sharing octahedral tilt angles are 80°.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Nd(NiSb)2 by Materials Project

Nd(NiSb)2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Nd3+ is bonded in a distorted body-centered cubic geometry to eight equivalent Sb3- atoms. All Nd–Sb bond lengths are 3.41 Å. Ni+1.50+ is bonded to four equivalent Sb3- atoms to form a mixture of edge and corner-sharing NiSb4 tetrahedra. All Ni–Sb bond lengths are 2.50 Å. Sb3- is bonded in a 9-coordinate geometry to four equivalent Nd3+, four equivalent Ni+1.50+, and one Sb3- atom. The Sb–Sb bond length is 2.91 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Sm(NiSb)2 by Materials Project

Sm(NiSb)2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Sm2+ is bonded in a distorted body-centered cubic geometry to eight equivalent Sb3- atoms. All Sm–Sb bond lengths are 3.39 Å. Ni2+ is bonded to four equivalent Sb3- atoms to form a mixture of corner and edge-sharing NiSb4 tetrahedra. All Ni–Sb bond lengths are 2.49 Å. Sb3- is bonded in a 9-coordinate geometry to four equivalent Sm2+, four equivalent Ni2+, and one Sb3- atom. The Sb–Sb bond length is 2.88 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Eu(NiSb)2 by Materials Project

Eu(NiSb)2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Eu2+ is bonded in a distorted body-centered cubic geometry to eight equivalent Sb3- atoms. All Eu–Sb bond lengths are 3.44 Å. Ni2+ is bonded to four equivalent Sb3- atoms to form a mixture of edge and corner-sharing NiSb4 tetrahedra. All Ni–Sb bond lengths are 2.51 Å. Sb3- is bonded in a 9-coordinate geometry to four equivalent Eu2+, four equivalent Ni2+, and one Sb3- atom. The Sb–Sb bond length is 2.95 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on NiSb by Materials Project

NiSb is Tungsten Carbide-like structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. Ni2+ is bonded to six equivalent Sb2- atoms to form a mixture of face, edge, and corner-sharing NiSb6 octahedra. The corner-sharing octahedral tilt angles are 52°. All Ni–Sb bond lengths are 2.62 Å. Sb2- is bonded in a 6-coordinate geometry to six equivalent Ni2+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Nd(NiSb)2 by Materials Project

Nd(NiSb)2 crystallizes in the tetragonal P4/nmm space group. The structure is three-dimensional. Nd3+ is bonded in a 8-coordinate geometry to eight Sb3- atoms. There are four shorter (3.37 Å) and four longer (3.46 Å) Nd–Sb bond lengths. There are two inequivalent Ni+1.50+ sites. In the first Ni+1.50+ site, Ni+1.50+ is bonded in a 5-coordinate geometry to five Sb3- atoms. There are one shorter (2.51 Å) and four longer (2.57 Å) Ni–Sb bond lengths. In the second Ni+1.50+ site, Ni+1.50+ is bonded to four equivalent Sb3- atoms to form a mixture of edge and corner-sharing NiSb4 tetrahedra. All Ni–Sb bond lengths are 2.57 Å. There are two inequivalent Sb3- sites. In the first Sb3- site, Sb3- is bonded in a 9-coordinate geometry to four equivalent Nd3+ and five Ni+1.50+ atoms. In the second Sb3- site, Sb3- is bonded in a 4-coordinate geometry to four equivalent Nd3+ and four equivalent Ni+1.50+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Pr(NiSb)2 by Materials Project

PrNi2Sb2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Pr3+ is bonded in a distorted body-centered cubic geometry to eight equivalent Sb3- atoms. All Pr–Sb bond lengths are 3.43 Å. Ni+1.50+ is bonded to four equivalent Sb3- atoms to form a mixture of corner and edge-sharing NiSb4 tetrahedra. All Ni–Sb bond lengths are 2.50 Å. Sb3- is bonded in a 9-coordinate geometry to four equivalent Pr3+, four equivalent Ni+1.50+, and one Sb3- atom. The Sb–Sb bond length is 2.92 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Gd(NiSb)2 by Materials Project

GdNi2Sb2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Gd3+ is bonded in a distorted body-centered cubic geometry to eight equivalent Sb3- atoms. All Gd–Sb bond lengths are 3.38 Å. Ni+1.50+ is bonded to four equivalent Sb3- atoms to form a mixture of edge and corner-sharing NiSb4 tetrahedra. All Ni–Sb bond lengths are 2.49 Å. Sb3- is bonded in a 9-coordinate geometry to four equivalent Gd3+, four equivalent Ni+1.50+, and one Sb3- atom. The Sb–Sb bond length is 2.87 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Sr(NiSb)2 by Materials Project

SrNi2Sb2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Sr2+ is bonded in a distorted body-centered cubic geometry to eight equivalent Sb3- atoms. All Sr–Sb bond lengths are 3.51 Å. Ni2+ is bonded to four equivalent Sb3- atoms to form a mixture of edge and corner-sharing NiSb4 tetrahedra. All Ni–Sb bond lengths are 2.53 Å. Sb3- is bonded in a 9-coordinate geometry to four equivalent Sr2+, four equivalent Ni2+, and one Sb3- atom. The Sb–Sb bond length is 3.06 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Opening the Bandgap of Metallic Half-Heuslers via the Introduction of d–d Orbital Interactions

Half-Heusler compounds with semiconducting behavior have been developed as high-performance thermoelectric materials for power generation. Many half-Heusler compounds also exhibit metallic behavior without a bandgap and thus inferior thermoelectric performance. Here, taking metallic half-Heusler MgNiSb as an example, a bandgap opening strategy is proposed by introducing the d–d orbital interactions, which enables the opening of the bandgap and the improvement of the thermoelectric performance. The width of the bandgap can be engineered by tuning the strength of the d–d orbital interactions. The conduction type and the carrier density can also be modulated in the Mg 1- x Ti x NiSb system. Both improved n-type and p-type thermoelectric properties are realized, which are much higher than that of the metallic MgNiSb. The proposed bandgap opening strategy can be employed to design and develop new half-Heusler semiconductors for functional and energy applications.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Ambient and High Pressure CuNiSb 2 : Metal-Ordered and Metal-Disordered NiAs-Type Derivative Pnictides

The mineral Zlatogorite, CuNiSb 2 , was synthesized in the laboratory for the first time by annealing elements at ambient pressure (CuNiSb 2 -AP). Rietveld refinement of synchrotron powder X-ray diffraction data indicates that CuNiSb 2 -AP crystallizes in the NiAs-derived structure ( P 3 m 1, #164) with Cu and Ni ordering. The structure consists of alternate NiSb 6 and CuSb 6 octahedral layers via face-sharing. The formation of such structure instead of metal disordered NiAs-type structure ( P 6 3 / mm c, #194) is validated by the lower energy of the ordered phase by first-principle calculations. Interatomic crystal orbital Hamilton population, electron localization function, and charge density analysis reveal strong Ni-Sb, Cu-Sb, and Cu-Ni bonding and long weak Sb-Sb interactions in CuNiSb 2 -AP. The magnetic measurement indicates that CuNiSb 2 -AP is Pauli paramagnetic. First-principle calculations and experimental electrical resistivity measurements reveal that CuNiSb 2 -AP is a metal. The low Seebeck coefficient and large thermal conductivity suggest that CuNiSb 2 is not a potential thermoelectric material. Single crystals were grown by chemical vapor transport. The high pressure sample (CuNiSb 2 -8 GPa) was prepared by pressing CuNiSb 2 -AP at 700 °C and 8 GPa. However, the structures of single crystal and CuNiSb 2 -8 GPa are best fit with a disordered metal structure in the P 3 m 1 space group, corroborated by transmission electron microscopy.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1998

Use of Microgravity to Control the Microstructure of Eutectics

This grant began in June of 1996. Its long term goal is to be able to control the microstructure of directionally solidified eutectic alloys, through an improved understanding of the influence of convection. The primary objective of the present projects is to test hypotheses for the reported influence of microgravity on the microstructure of three fibrous eutectics (MnBi-Bi, InSb-NiSb, Al3Ni-Al). A secondary objective is to determine the influence of convection on the microstructure of other eutectic alloys. Two doctoral students and a masters student supported as a teaching assistant were recruited for this research. Techniques were developed for directional solidification of MnBi-Bi eutectics with periodic application of current pulses to produce an oscillatory freezing rate. Image analysis techniques were developed to obtain the variation in MnBi fiber spacing, which was found to be normally distributed. The mean and standard deviation of fiber spacing were obtained for several freezing conditions. Eighteen ampoules were prepared for use in the gradient freeze furnace QUELD developed at Queen's University for use in microgravity. Nine of these ampoules will be solidified soon at Queen's in a ground-based model. We hope to solidify the other nine in the QUELD that is mounted on the Canadian Microgravity Isolation Mount on MIR. Techniques are being developed for directional solidification of the Al-Si eutectic at different freezing rates, with and without application of accelerated crucible rotation to induce convection. For the first time, theoretical methods are being developed to analyze eutectic solidification with an oscillatory freezing rate. In a classical sharp-interface model, we found that an oscillatory freezing rate increases the deviation of the average interfacial composition from the eutectic, and increases the undercooling of the two phases by different amounts. This would be expected to change the volume fraction solidifying and the fiber spacing. Because of difficulties in tracking the freezing interfaces of the two solid phases, a phase-field model is also being developed. A paper demonstrating application of phase field methods to periodic structures has been submitted for publication.

Wilcox, William R.↗