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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
NASA NTRS1979

A proposed physical model for the impregnated tungsten cathode based on Auger surface studies of the Ba-O-W system

Auger spectra and work function measurements are used to study the surface reactions between tungsten surface and adsorbed layers of barium, and barium and oxygen. The barium on an impregnated tungsten cathod seems to be an intermediate state, probably a coadsorbed barium-oxygen layer on tungsten. A slightly revised version of the previously suggested (1976) impregnated tungsten cathode model is proposed. This revised model assumes that the cathode surface during life has an adsorbed surface layer of a monolayer or less of both barium and oxygen on the surface. At end of life, steep drop in electron emission and resultant cathode failure occur. Recent NASA life test results on TWT type tubes are reported and explained by the proposed model.

Forman, R.↗
DOE OSTI2020

Materials Data on Ba3W2O9 by Materials Project

Ba3W2O9 crystallizes in the trigonal R-3c space group. The structure is three-dimensional. Ba2+ is bonded to twelve O2- atoms to form BaO12 cuboctahedra that share corners with six equivalent BaO12 cuboctahedra, corners with four equivalent WO6 octahedra, faces with eight equivalent BaO12 cuboctahedra, and faces with four equivalent WO6 octahedra. The corner-sharing octahedra tilt angles range from 6–29°. There are a spread of Ba–O bond distances ranging from 2.87–3.09 Å. W6+ is bonded to six O2- atoms to form distorted WO6 octahedra that share corners with six equivalent BaO12 cuboctahedra, faces with six equivalent BaO12 cuboctahedra, and a faceface with one WO6 octahedra. There is three shorter (1.85 Å) and three longer (2.11 Å) W–O bond length. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted L-shaped geometry to four equivalent Ba2+ and two equivalent W6+ atoms. In the second O2- site, O2- is bonded in a distorted single-bond geometry to four equivalent Ba2+ and one W6+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on BaWO4 by Materials Project

BaWO4 is Zircon-like structured and crystallizes in the tetragonal I4_1/a space group. The structure is three-dimensional. Ba2+ is bonded in a 8-coordinate geometry to eight equivalent O2- atoms. There are four shorter (2.79 Å) and four longer (2.83 Å) Ba–O bond lengths. W6+ is bonded in a tetrahedral geometry to four equivalent O2- atoms. All W–O bond lengths are 1.82 Å. O2- is bonded in a 1-coordinate geometry to two equivalent Ba2+ and one W6+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ba3WO6 by Materials Project

Ba3WO6 crystallizes in the triclinic P1 space group. The structure is three-dimensional. there are six inequivalent Ba2+ sites. In the first Ba2+ site, Ba2+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Ba–O bond distances ranging from 2.56–3.01 Å. In the second Ba2+ site, Ba2+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Ba–O bond distances ranging from 2.56–2.97 Å. In the third Ba2+ site, Ba2+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Ba–O bond distances ranging from 2.55–3.11 Å. In the fourth Ba2+ site, Ba2+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Ba–O bond distances ranging from 2.66–3.06 Å. In the fifth Ba2+ site, Ba2+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Ba–O bond distances ranging from 2.66–3.09 Å. In the sixth Ba2+ site, Ba2+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of Ba–O bond distances ranging from 2.51–2.90 Å. There are two inequivalent W6+ sites. In the first W6+ site, W6+ is bonded in an octahedral geometry to six O2- atoms. There are a spread of W–O bond distances ranging from 1.93–2.03 Å. In the second W6+ site, W6+ is bonded in a trigonal bipyramidal geometry to five O2- atoms. There are a spread of W–O bond distances ranging from 1.85–2.01 Å. There are twelve inequivalent O2- sites. In the first O2- site, O2- is bonded to three Ba2+ and one W6+ atom to form distorted corner-sharing OBa3W tetrahedra. In the second O2- site, O2- is bonded in a 5-coordinate geometry to four Ba2+ and one W6+ atom. In the third O2- site, O2- is bonded in a 4-coordinate geometry to three Ba2+ and one W6+ atom. In the fourth O2- site, O2- is bonded in a 1-coordinate geometry to four Ba2+ and one W6+ atom. In the fifth O2- site, O2- is bonded in a 1-coordinate geometry to three Ba2+ and one W6+ atom. In the sixth O2- site, O2- is bonded in a 4-coordinate geometry to three Ba2+ and one W6+ atom. In the seventh O2- site, O2- is bonded in a 1-coordinate geometry to three Ba2+ and one W6+ atom. In the eighth O2- site, O2- is bonded in a 5-coordinate geometry to five Ba2+ atoms. In the ninth O2- site, O2- is bonded in a 5-coordinate geometry to four Ba2+ and one W6+ atom. In the tenth O2- site, O2- is bonded in a 4-coordinate geometry to three Ba2+ and one W6+ atom. In the eleventh O2- site, O2- is bonded in a 4-coordinate geometry to three Ba2+ and one W6+ atom. In the twelfth O2- site, O2- is bonded to three Ba2+ and one W6+ atom to form distorted corner-sharing OBa3W tetrahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ba2WO6 by Materials Project

Ba2WO6 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. there are two inequivalent Ba sites. In the first Ba site, Ba is bonded in a 9-coordinate geometry to nine O atoms. There are a spread of Ba–O bond distances ranging from 2.65–3.08 Å. In the second Ba site, Ba is bonded in a 8-coordinate geometry to eight O atoms. There are a spread of Ba–O bond distances ranging from 2.62–2.94 Å. W is bonded to six O atoms to form distorted edge-sharing WO6 octahedra. There are a spread of W–O bond distances ranging from 1.86–2.14 Å. There are six inequivalent O sites. In the first O site, O is bonded in a 3-coordinate geometry to three Ba atoms. In the second O site, O is bonded in a 4-coordinate geometry to two Ba and two equivalent W atoms. In the third O site, O is bonded in a 4-coordinate geometry to three Ba and one W atom. In the fourth O site, O is bonded in a 4-coordinate geometry to three Ba and one W atom. In the fifth O site, O is bonded in a 4-coordinate geometry to three Ba and one W atom. In the sixth O site, O is bonded in a distorted single-bond geometry to three Ba and one W atom.

36 MATERIALS SCIENCE↗