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At least 235 records · Page 13
All sourcesNASA NTRSDOE OSTI
NASA NTRS1990

Yttrium enrichment and improved magnetic properties in partially melted Y-Ba-Cu-O materials

The yttrium-rich compositions in the Y-Ba-Cu-O system were mapped out in a systematic manner to quantify their magnetic properties and to correlate them with the microstructure and phase composition as determined by scanning electron microscopy and X-ray diffraction analysis. It is found that the microstructure of Y-Ba-Cu-O compositions is a sensitive function of both their composition and processing conditions. Measurements of magnetic susceptibility and maximum (low-field) and remanent magnetization for the system Y:Ba:Cu = x:2:3 show highest values for x = 2. The corresponding structures involve numerous small crystals of Y2BaCuO5 (211) embedded in highly ordered assemblages of continous YBa2Cu3O(7-y) (123) layers.

Alterescu, Sidney↗
NASA NTRS1995

On Ba(+) production in the CRIT 2 experiment

Analysis of partical data from the CRIT 2 experiment, studying Alfven's critical ionization velocity (CIV) effect, shows that the density of newly created ions (presumably Ba(+) from the shaped-charge beam) is consistent with the increase in total plasma density measured by the independent RF plasma probe on board (Swenson et al., 1990) at the most active time period. We model this ion production using the measured electron flux data and the neutral barium model of Stenbaek-Nielsen et al. (1990a). To identify the main source mechanisms which may contribute most to the barium ionization, a simple model for the barium ion density at the payload location is developed based on Liouvilles theorem. We estimate that the electron impact ionization is responsible for 90% of the barium ion production observed by CRIT 2 in the first release and up to 45% in the second release. By employing a two-state approximation calculation (Rapp and Francis, 1962), the Ba-O(+) charge exchange cross section is found to range from about 2.0 X 10(exp -17) sq cm at a velocity of 4 km/s to 2.0 X 10(exp -15) sq cm at a velocity of 20 km/s. This result suggests that the Ba-O(+) charge exchange is probably dominant among all the non-CIV ionization processes. By considering the charge exchange process in our density model, the barrium ion densities are calculated for the two releases on CRIT II. The comparison between the model results and the observed data is found to be resonably consistent if the cross sections, as calculated above, are multiplied by 0.3 for the first release and 1.0 for the second release. Our result suggests that the charge exchange process could be the most important non-CIV ionization mechanism in the CRIT II experiment and it should be considered carefully case by case in CIV experiments.

Liou, K.↗
NASA NTRS2002

A Statistical Analysis of Laser Ablated Ba(Sub 0.50)Sr(Sub 0.50)TiO(Sub 3)/LaAlO(Sub 3) Films for Microwave Applications

The NASA Glenn Research Center is constructing a 616 element scanning phased array antenna using thin film Ba(sub x)Sr(sub 1-x)TiO(sub 3) based phase shifters. A critical milestone is the production of 616 identical phase shifters at 19 GHz with [asymptotically equal to]4 dB insertion loss and at least 337.5 deg phase shift with 3 percent bandwidth. It is well known that there is a direct relationship between dielectric tuning and loss due to the Kramers-Kronig relationship and that film crystallinity and strain, affected by the substrate template, play an important role. Ba(sub 0.50)Sr(sub 0.50)TiO (sub 3) films, nominally 400 nm thick, were deposited on 48 0.25 mm thick, 5 cm diameter LaAlO(sub 3) wafers. Although previous results suggested that Mn-doped films on MgO were intrinsically superior in terms of phase shift per unit loss, for this application phase shift per unit length was more important. The composition was selected as a compromise between tuning and loss for room temperature operation (e.g. crystallinity progressively degrades for Ba concentrations in excess of 30 percent). As a prelude to fabricating the array, it was necessary to process, screen, and inventory a large number of samples. Variable angle ellipsometry was used to characterize refractive index and film thickness across each wafer. Microstructural properties of the thin films were characterized using high resolution X-ray diffractometry. Finally, prototype phase shifters and resonators were patterned on each wafer and RE probed to measure tuning as a function of dc bias voltage as well as peak (0 field) permittivity and unloaded Q. The relationship among film quality and uniformity and performance is analyzed. This work presents the first statistically relevant study of film quality and microwave performance and represents a milestone towards commercialization of thin ferroelectric films for microwave applications.

Ferroelectric thin films↗
NASA NTRS2010

Analysis of Jupiter's Oval BA: A Streamlined Approach

We present a novel method of constructing streamlines to derive wind speeds within jovian vortices and demonstrate its application to Oval BA for 2001 pre-reddened Cassini flyby data, 2007 post-reddened New Horizons flyby data, and 1998 Galileo data of precursor Oval DE. Our method, while automated, attempts to combine the advantages of both automated and manual cloud tracking methods. The southern maximum wind speed of Oval BA does not show significant changes between these data sets to within our measurement uncertainty. The northern maximum dries appear to have increased in strength during this time interval, tvhich likely correlates with the oval's return to a symmetric shape. We demonstrate how the use of closed streamlines can provide measurements of vorticity averaged over the encircled area with no a priori assumptions concerning oval shape. We find increased averaged interior vorticity between pre- and post-reddened Oval BA, with the precursor Oval DE occupying a middle value of vorticity between these two.

Sussman, Michael G.↗
DOE OSTI2020

Materials Data on Ba(POs)2 by Materials Project

Ba(OsP)2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Ba2+ is bonded in a 8-coordinate geometry to eight equivalent Os2- atoms. All Ba–Os bond lengths are 3.69 Å. Os2- is bonded to four equivalent Ba2+ and four equivalent P1+ atoms to form a mixture of distorted corner, edge, and face-sharing OsBa4P4 tetrahedra. All Os–P bond lengths are 2.35 Å. P1+ is bonded in a 4-coordinate geometry to four equivalent Os2- atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ba(BeN)2 by Materials Project

Ba(BeN)2 crystallizes in the tetragonal I4/mcm space group. The structure is three-dimensional. Ba2+ is bonded in a 8-coordinate geometry to eight equivalent N3- atoms. All Ba–N bond lengths are 3.00 Å. Be2+ is bonded in a trigonal planar geometry to three equivalent N3- atoms. There is one shorter (1.65 Å) and two longer (1.69 Å) Be–N bond length. N3- is bonded in a 3-coordinate geometry to four equivalent Ba2+ and three equivalent Be2+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ba(AlS2)2 by Materials Project

BaAl2S4 crystallizes in the cubic Pa-3 space group. The structure is three-dimensional. there are two inequivalent Ba2+ sites. In the first Ba2+ site, Ba2+ is bonded in a 6-coordinate geometry to six S2- atoms. There are three shorter (3.22 Å) and three longer (3.30 Å) Ba–S bond lengths. In the second Ba2+ site, Ba2+ is bonded to twelve S2- atoms to form BaS12 cuboctahedra that share corners with twelve equivalent AlS4 tetrahedra and edges with six equivalent AlS4 tetrahedra. There are six shorter (3.62 Å) and six longer (3.64 Å) Ba–S bond lengths. Al3+ is bonded to four S2- atoms to form AlS4 tetrahedra that share corners with two equivalent BaS12 cuboctahedra, corners with four equivalent AlS4 tetrahedra, and an edgeedge with one BaS12 cuboctahedra. There are a spread of Al–S bond distances ranging from 2.25–2.28 Å. There are two inequivalent S2- sites. In the first S2- site, S2- is bonded in a 2-coordinate geometry to two Ba2+ and two equivalent Al3+ atoms. In the second S2- site, S2- is bonded in a 2-coordinate geometry to two Ba2+ and two equivalent Al3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ba(As3Pt2)2 by Materials Project

Ba(Pt2As3)2 crystallizes in the monoclinic C2/c space group. The structure is three-dimensional. Ba2+ is bonded to six Pt2- atoms to form distorted corner-sharing BaPt6 pentagonal pyramids. There are a spread of Ba–Pt bond distances ranging from 3.01–3.23 Å. There are three inequivalent Pt2- sites. In the first Pt2- site, Pt2- is bonded to six As1+ atoms to form corner-sharing PtAs6 octahedra. The corner-sharing octahedra tilt angles range from 59–65°. There are four shorter (2.54 Å) and two longer (2.56 Å) Pt–As bond lengths. In the second Pt2- site, Pt2- is bonded to two equivalent Ba2+ and four As1+ atoms to form PtBa2As4 octahedra that share corners with ten PtAs6 octahedra and edges with four PtBa2As4 octahedra. The corner-sharing octahedra tilt angles range from 22–109°. There are a spread of Pt–As bond distances ranging from 2.49–2.56 Å. In the third Pt2- site, Pt2- is bonded to two equivalent Ba2+ and four As1+ atoms to form PtBa2As4 octahedra that share corners with ten PtAs6 octahedra and edges with four equivalent PtBa2As4 octahedra. The corner-sharing octahedra tilt angles range from 33–82°. There are two shorter (2.48 Å) and two longer (2.54 Å) Pt–As bond lengths. There are three inequivalent As1+ sites. In the first As1+ site, As1+ is bonded in a trigonal non-coplanar geometry to three Pt2- atoms. In the second As1+ site, As1+ is bonded in a trigonal planar geometry to three Pt2- atoms. In the third As1+ site, As1+ is bonded in a trigonal non-coplanar geometry to three Pt2- atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ba(SiIr)2 by Materials Project

Ba(IrSi)2 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. Ba2+ is bonded in a 6-coordinate geometry to six Si4- atoms. There are a spread of Ba–Si bond distances ranging from 3.38–3.53 Å. There are two inequivalent Ir3+ sites. In the first Ir3+ site, Ir3+ is bonded to four Si4- atoms to form a mixture of corner and edge-sharing IrSi4 tetrahedra. There are a spread of Ir–Si bond distances ranging from 2.34–2.44 Å. In the second Ir3+ site, Ir3+ is bonded to four Si4- atoms to form a mixture of distorted corner and edge-sharing IrSi4 tetrahedra. There are three shorter (2.39 Å) and one longer (2.44 Å) Ir–Si bond lengths. There are two inequivalent Si4- sites. In the first Si4- site, Si4- is bonded in a 4-coordinate geometry to three equivalent Ba2+ and four Ir3+ atoms. In the second Si4- site, Si4- is bonded in a 4-coordinate geometry to three equivalent Ba2+ and four Ir3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ba(Ni5P3)2 by Materials Project

Ba(Ni5P3)2 crystallizes in the orthorhombic Cmce space group. The structure is three-dimensional. Ba2+ is bonded in a 12-coordinate geometry to twelve P3- atoms. There are a spread of Ba–P bond distances ranging from 3.25–3.70 Å. There are four inequivalent Ni+1.60+ sites. In the first Ni+1.60+ site, Ni+1.60+ is bonded to four P3- atoms to form a mixture of distorted corner and edge-sharing NiP4 trigonal pyramids. There are a spread of Ni–P bond distances ranging from 2.31–2.47 Å. In the second Ni+1.60+ site, Ni+1.60+ is bonded to four P3- atoms to form a mixture of distorted corner and edge-sharing NiP4 tetrahedra. There are two shorter (2.26 Å) and two longer (2.35 Å) Ni–P bond lengths. In the third Ni+1.60+ site, Ni+1.60+ is bonded to four P3- atoms to form a mixture of corner and edge-sharing NiP4 tetrahedra. There are a spread of Ni–P bond distances ranging from 2.19–2.27 Å. In the fourth Ni+1.60+ site, Ni+1.60+ is bonded to four P3- atoms to form a mixture of corner and edge-sharing NiP4 tetrahedra. There are a spread of Ni–P bond distances ranging from 2.21–2.33 Å. There are three inequivalent P3- sites. In the first P3- site, P3- is bonded in a 6-coordinate geometry to two equivalent Ba2+ and six Ni+1.60+ atoms. In the second P3- site, P3- is bonded in a 6-coordinate geometry to three equivalent Ba2+ and six Ni+1.60+ atoms. In the third P3- site, P3- is bonded in a 9-coordinate geometry to one Ba2+ and eight Ni+1.60+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ba(Cu2P)4 by Materials Project

Ba(Cu2P)4 crystallizes in the tetragonal I4/m space group. The structure is three-dimensional. Ba2+ is bonded in a body-centered cubic geometry to eight equivalent P3- atoms. All Ba–P bond lengths are 3.42 Å. There are two inequivalent Cu+1.25+ sites. In the first Cu+1.25+ site, Cu+1.25+ is bonded in a 4-coordinate geometry to four equivalent P3- atoms. There are a spread of Cu–P bond distances ranging from 2.27–2.60 Å. In the second Cu+1.25+ site, Cu+1.25+ is bonded in a distorted trigonal planar geometry to three equivalent P3- atoms. There are one shorter (2.32 Å) and two longer (2.36 Å) Cu–P bond lengths. P3- is bonded in a 9-coordinate geometry to two equivalent Ba2+ and seven Cu+1.25+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ba(Cu2As)4 by Materials Project

Ba(Cu2As)4 crystallizes in the tetragonal I4/m 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 3.43 Å. There are two inequivalent Cu+1.25+ sites. In the first Cu+1.25+ site, Cu+1.25+ is bonded in a 3-coordinate geometry to three equivalent As3- atoms. There are one shorter (2.44 Å) and two longer (2.51 Å) Cu–As bond lengths. In the second Cu+1.25+ site, Cu+1.25+ is bonded in a 4-coordinate geometry to four equivalent As3- atoms. There are a spread of Cu–As bond distances ranging from 2.43–2.60 Å. As3- is bonded in a 9-coordinate geometry to two equivalent Ba2+ and seven Cu+1.25+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ba(Cu2As)2 by Materials Project

Ba(Cu2As)2 crystallizes in the trigonal R-3m space group. The structure is three-dimensional. Ba2+ is bonded to six equivalent As3- atoms to form edge-sharing BaAs6 octahedra. All Ba–As bond lengths are 3.30 Å. There are two inequivalent Cu1+ sites. In the first Cu1+ site, Cu1+ is bonded in a distorted trigonal planar geometry to three equivalent As3- atoms. All Cu–As bond lengths are 2.49 Å. In the second Cu1+ site, Cu1+ is bonded in a 1-coordinate geometry to four equivalent As3- atoms. There are one shorter (2.46 Å) and three longer (2.79 Å) Cu–As bond lengths. As3- is bonded in a 10-coordinate geometry to three equivalent Ba2+ and seven Cu1+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ba(TbTe2)2 by Materials Project

Ba(TbTe2)2 crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. Ba2+ is bonded in a 8-coordinate geometry to eight Te2- atoms. There are a spread of Ba–Te bond distances ranging from 3.57–3.76 Å. There are two inequivalent Tb3+ sites. In the first Tb3+ site, Tb3+ is bonded to six Te2- atoms to form a mixture of edge and corner-sharing TbTe6 octahedra. The corner-sharing octahedra tilt angles range from 47–59°. There are a spread of Tb–Te bond distances ranging from 3.07–3.15 Å. In the second Tb3+ site, Tb3+ is bonded to six Te2- atoms to form a mixture of edge and corner-sharing TbTe6 octahedra. The corner-sharing octahedra tilt angles range from 47–59°. There are a spread of Tb–Te bond distances ranging from 3.08–3.14 Å. There are four inequivalent Te2- sites. In the first Te2- site, Te2- is bonded to two equivalent Ba2+ and three Tb3+ atoms to form a mixture of distorted edge and corner-sharing TeBa2Tb3 trigonal bipyramids. In the second Te2- site, Te2- is bonded to two equivalent Ba2+ and three equivalent Tb3+ atoms to form a mixture of distorted edge and corner-sharing TeBa2Tb3 square pyramids. In the third Te2- site, Te2- is bonded in a 5-coordinate geometry to two equivalent Ba2+ and three Tb3+ atoms. In the fourth Te2- site, Te2- is bonded in a 5-coordinate geometry to two equivalent Ba2+ and three equivalent Tb3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ba(Ni2B)6 by Materials Project

Ba(Ni2B)6 crystallizes in the trigonal R-3m space group. The structure is three-dimensional. Ba2+ is bonded in a hexagonal planar geometry to six equivalent B3- atoms. All Ba–B bond lengths are 3.26 Å. There are two inequivalent Ni+1.33+ sites. In the first Ni+1.33+ site, Ni+1.33+ is bonded to four equivalent B3- atoms to form a mixture of distorted corner and edge-sharing NiB4 tetrahedra. There are two shorter (2.04 Å) and two longer (2.16 Å) Ni–B bond lengths. In the second Ni+1.33+ site, Ni+1.33+ is bonded in a T-shaped geometry to three equivalent B3- atoms. There are two shorter (2.06 Å) and one longer (2.07 Å) Ni–B bond lengths. B3- is bonded in a 7-coordinate geometry to one Ba2+ and seven Ni+1.33+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ba(HoTe2)2 by Materials Project

Ba(HoTe2)2 crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. Ba2+ is bonded in a 8-coordinate geometry to eight Te2- atoms. There are a spread of Ba–Te bond distances ranging from 3.56–3.75 Å. There are two inequivalent Ho3+ sites. In the first Ho3+ site, Ho3+ is bonded to six Te2- atoms to form a mixture of edge and corner-sharing HoTe6 octahedra. The corner-sharing octahedra tilt angles range from 47–58°. There are a spread of Ho–Te bond distances ranging from 3.05–3.13 Å. In the second Ho3+ site, Ho3+ is bonded to six Te2- atoms to form a mixture of edge and corner-sharing HoTe6 octahedra. The corner-sharing octahedra tilt angles range from 47–58°. There are a spread of Ho–Te bond distances ranging from 3.05–3.12 Å. There are four inequivalent Te2- sites. In the first Te2- site, Te2- is bonded to two equivalent Ba2+ and three Ho3+ atoms to form a mixture of distorted edge and corner-sharing TeBa2Ho3 trigonal bipyramids. In the second Te2- site, Te2- is bonded to two equivalent Ba2+ and three equivalent Ho3+ atoms to form a mixture of distorted edge and corner-sharing TeBa2Ho3 square pyramids. In the third Te2- site, Te2- is bonded in a 5-coordinate geometry to two equivalent Ba2+ and three Ho3+ atoms. In the fourth Te2- site, Te2- is bonded in a 5-coordinate geometry to two equivalent Ba2+ and three equivalent Ho3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ba(DyTe2)2 by Materials Project

Ba(DyTe2)2 crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. Ba2+ is bonded in a 8-coordinate geometry to eight Te2- atoms. There are a spread of Ba–Te bond distances ranging from 3.56–3.75 Å. There are two inequivalent Dy3+ sites. In the first Dy3+ site, Dy3+ is bonded to six Te2- atoms to form a mixture of corner and edge-sharing DyTe6 octahedra. The corner-sharing octahedra tilt angles range from 47–59°. There are a spread of Dy–Te bond distances ranging from 3.06–3.14 Å. In the second Dy3+ site, Dy3+ is bonded to six Te2- atoms to form a mixture of corner and edge-sharing DyTe6 octahedra. The corner-sharing octahedra tilt angles range from 47–59°. There are a spread of Dy–Te bond distances ranging from 3.06–3.13 Å. There are four inequivalent Te2- sites. In the first Te2- site, Te2- is bonded to two equivalent Ba2+ and three Dy3+ atoms to form a mixture of distorted corner and edge-sharing TeBa2Dy3 trigonal bipyramids. In the second Te2- site, Te2- is bonded to two equivalent Ba2+ and three equivalent Dy3+ atoms to form a mixture of distorted corner and edge-sharing TeBa2Dy3 square pyramids. In the third Te2- site, Te2- is bonded in a 5-coordinate geometry to two equivalent Ba2+ and three Dy3+ atoms. In the fourth Te2- site, Te2- is bonded in a 5-coordinate geometry to two equivalent Ba2+ and three equivalent Dy3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ba(ErTe2)2 by Materials Project

Ba(ErTe2)2 crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. Ba2+ is bonded in a 8-coordinate geometry to eight Te2- atoms. There are a spread of Ba–Te bond distances ranging from 3.56–3.74 Å. There are two inequivalent Er3+ sites. In the first Er3+ site, Er3+ is bonded to six Te2- atoms to form a mixture of edge and corner-sharing ErTe6 octahedra. The corner-sharing octahedra tilt angles range from 47–58°. There are a spread of Er–Te bond distances ranging from 3.04–3.13 Å. In the second Er3+ site, Er3+ is bonded to six Te2- atoms to form a mixture of edge and corner-sharing ErTe6 octahedra. The corner-sharing octahedra tilt angles range from 47–58°. There are a spread of Er–Te bond distances ranging from 3.04–3.11 Å. There are four inequivalent Te2- sites. In the first Te2- site, Te2- is bonded to two equivalent Ba2+ and three Er3+ atoms to form a mixture of distorted edge and corner-sharing TeBa2Er3 trigonal bipyramids. In the second Te2- site, Te2- is bonded to two equivalent Ba2+ and three equivalent Er3+ atoms to form a mixture of distorted edge and corner-sharing TeBa2Er3 square pyramids. In the third Te2- site, Te2- is bonded in a 5-coordinate geometry to two equivalent Ba2+ and three Er3+ atoms. In the fourth Te2- site, Te2- is bonded in a 5-coordinate geometry to two equivalent Ba2+ and three equivalent Er3+ atoms.

36 MATERIALS SCIENCE↗