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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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5 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on Ga2S3 by Materials Project

Ga2S3 crystallizes in the monoclinic Cc space group. The structure is three-dimensional. there are two inequivalent Ga3+ sites. In the first Ga3+ site, Ga3+ is bonded to four S2- atoms to form corner-sharing GaS4 tetrahedra. There are one shorter (2.22 Å) and three longer (2.35 Å) Ga–S bond lengths. In the second Ga3+ site, Ga3+ is bonded to four S2- atoms to form corner-sharing GaS4 tetrahedra. There are a spread of Ga–S bond distances ranging from 2.23–2.36 Å. There are three inequivalent S2- sites. In the first S2- site, S2- is bonded in a water-like geometry to two Ga3+ atoms. In the second S2- site, S2- is bonded in a trigonal non-coplanar geometry to three Ga3+ atoms. In the third S2- site, S2- is bonded in a trigonal non-coplanar geometry to three Ga3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ga2S3 by Materials Project

Ga2S3 crystallizes in the monoclinic Cc space group. The structure is three-dimensional. there are two inequivalent Ga3+ sites. In the first Ga3+ site, Ga3+ is bonded to four S2- atoms to form corner-sharing GaS4 tetrahedra. There are a spread of Ga–S bond distances ranging from 2.22–2.36 Å. In the second Ga3+ site, Ga3+ is bonded to four S2- atoms to form corner-sharing GaS4 tetrahedra. There are a spread of Ga–S bond distances ranging from 2.22–2.36 Å. There are three inequivalent S2- sites. In the first S2- site, S2- is bonded in a trigonal non-coplanar geometry to three Ga3+ atoms. In the second S2- site, S2- is bonded in a trigonal non-coplanar geometry to three Ga3+ atoms. In the third S2- site, S2- is bonded in a water-like geometry to two Ga3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Temperature-dependent growth of hexagonal and monoclinic gallium sulfide films by pulsed-laser deposition

We demonstrate the selective, pulsed-laser deposition of hexagonal GaS and monoclinic Ga2S3 films on sapphire substrates from a single Ga 2 S 3 target in high-vacuum conditions. Growth at substrate temperatures below 550 °C causes GaS film formation, which indicates non-stoichiometric transfer from the target to the film. Surprisingly, stoichiometric transfer occurs at substrate temperatures above 650 °C with monoclinic Ga 2 S 3 as the preferred, higher S-content phase. Through a series of growth and annealing experiments, we show that GaS nucleation under S-deficient conditions leads to the preferred growth of this layered, hexagonal phase below 550 °C. Furthermore, GaS films annealed above 650 °C under high vacuum are transformed to Ga 2 S 3 , reflecting the greater stability of the monoclinic phase. By first growing Ga 2 S 3 at a higher temperature and subsequently growing GaS at a lower temperature, we can fabricate GaS/Ga 2 S 3 heterostructures in a single growth process.

36 MATERIALS SCIENCE↗
NASA NTRS1989

Encapsulated diffusion of sulphur into InP

This talk outlines a simple process for the fabrication of n(+)-p solar cells in indium phosphide. Large area cells (greater than 0.25 sq cm) have been made by this process, with a photovoltaic conversion efficiency of 15.21 percent under AM0 conditions of illumination. An ideality factor of 1.1 and a saturation current density of 8 x 10 to the minus 15th power A/sq cm have been observed for these cells. The technique for cell fabrication involves the diffusion of sulfur into InP by an open tube process, and gives highly reproducible results from run to run. A vacuum-deposited layer of gallium sulphide (Ga2S3) was used as the source for sulfur diffusion, with a chemically vapor deposited SiO2 cap layer to prevent decomposition of the InP surface during heat treatment. Diffusions were carried out in a flowing nitrogen ambient at 585 to 708 C, and characterized by their surface carrier concentration and the diffusion constant. The diffusion profile for sulfur in InP is estimated to be of the complementary error function type. The activation energy of the diffusion was estimated to be 1.94 eV. The technique described here is ideally suited for the fabrication of shallow n(+)-p junctions in InP, and has been used for space-borne solar cells.

Parat, K. K.↗
NASA NTRS2002

Development of Chemically and Thermally Robust Lithium Fast Ion Conducting Chalcogenide Glasses

In this project, a new research thrust into the development of an entirely new class of FIC glasses has begun that may lead to a new set of optimized thin-film lithium ion conducting materials. New chemically robust FIC glasses are being prepared that are expected to exhibit unusually high chemical and electrochemical stability. New thermally robust FIC glasses are being prepared that exhibit softening points in excess of 500 C which will dramatically expand the usable operating temperature range of batteries, fuel-cells, and sensors using such electrolytes. Glasses are being explored in the general compositional series xLi2S+ yGa2S3 + (1-x-y)GeS2. Li2S is added as the source of the conductive lithium ions. GeS2 is the base glass-forming phase and the trivalent sulfides, Ga2S3, is added to increase the "refractoniness" of the glass, that is to significantly increase the softening point of the glass as well as its chemical stability. By optimizing the composition of the glass, new glasses and glass-ceramic FIC materials have been prepared with softening points in excess of 500 C and conductivities above 10(exp -3)/Ohm cm at room temperature. These latter attributes are currently not available in any FIC glasses to date.

Martin, Steve W.↗