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At least 379 records · Page 21
All sourcesNASA NTRSDOE OSTI
NASA NTRS1999

Epitaxial Ferroelectric Ba(0.5)Sr(0.5)TiO3 Thin Films for Room-Temperature High-Frequency Tunable Element Applications

Perovskite Ba(0.5)SR(0.5)TiO3 thin films have been synthesized on (001) LaAl03 substrates by pulsed laser ablation. Extensive X-ray diffraction, rocking curve, and pole-figure studies suggest that the films are c-axis oriented and exhibit good in-plane relationship of <100>(sub BSTO)//<100>(sub LAO). Rutherford Backscattering Spectrometry studies indicate that the epitaxial films have excellent crystalline quality with an ion beam minimum yield chi(sub min) Of only 2.6 %. The dielectric property measurements by the interdigital technique at 1 MHz show room temperature values of the relative dielectric constant, epsilon(sub r), and loss tangent, tan(sub delta), of 1430 and 0.007 with no bias, and 960 and 0.001 with 35 V bias, respectively. The obtained data suggest that the as-grown Ba(0.5)SR(0.5)TiO3 films can be used for development of room-temperature high-frequency tunable elements.

Chen, C. L.↗
NASA NTRS2000

Current Status of Thin Film (Ba,Sr)TiO3 Tunable Microwave Components for RF Communications

The performance of proof-of-concept ferroelectric microwave devices has been moving steadily closer to the level needed for satellite and other rf communications applications. This paper will review recent progress at NASA Glenn in developing thin film Ba(x)Sr(1-x)TiO3 tunable micro-wave components for these applications. Phase shifters for phased array antennas, tunable filters and tunable oscillators employing microstrip and coupled microstrip configurations will be presented. Tunabilities, maximum dielectric constants, and phase shifter parameters will be discussed (e.g., coupled microstrip phase shifters with phase shift over 200 deg at 18 GHz and a figure of merit of 74.3 deg/dB). Issues of post-annealing, Mn-doping and Ba(x)Sr(1-x) TiO3 growth on sapphire and alumina substrates will be covered. The challenges of incorporating these devices into larger systems, such as yield, variability in phase shift and insertion loss, and protective coatings will also be addressed.

VanKeuls, F. W.↗
NASA NTRS2000

Current Status of Thin Film (Ba,Sr) TiO3 Tunable Microwave Components for RF Communications

The performance of proof-of-concept ferroelectric microwave devices has been moving steadily closer to the level needed for satellite and other rf communications applications. This paper will review recent progress at NASA Glenn in developing thin film Ba(x)Sr(1-x)TiO3 tunable microwave components for these applications. Phase shifters for phased array antennas, tunable filters and tunable oscillators employing microstrip and coupled microstrip configurations will be presented. Tunabilities, maximum dielectric constants, and phase shifter parameters will be discussed (e.g., coupled microstrip phase shifters with phase shift over 200 deg. at 18 GHz and a figure of merit of 74.3 deg./dB). Issues of postannealing, Mn-doping and Ba(x)Sr(1-x)TiO3 growth on sapphire and alumina substrates will be covered. The challenges of incorporating these devices into larger systems, such as yield, variability in phase shift and insertion loss, and protective coatings will also be addressed.

VanKeuls, F. W.↗
NASA NTRS2008

The 2008 Passage of Jupiter's Great Red Spot and Oval BA as Observed from Hubble/WFPC2

Hubble Space Telescope data of the passage of Jupiter's Great Red Spot (GRS) and Oval BA were acquired on May 15, June 28 (near closest approach), and July 8. Wind fields were measured from Wide Field Planetary Camera 2 (WFPC2) data with 10-hour separations before and after closest approach, and within the GRS with 40-minute separations on all three dates. Color information was also derived using 8 narrowband WFPC2 filters from 343 to 673-nm on all three dates. We will present the results of principal components and wind analyses and discuss unique features seen in this data set. In addition, we will highlight any changes observed in the GRS, Oval BA and their surroundings as a result of the passage, including the movement of a smaller red anticyclone from west of the GRS, around its southern periphery, and to the east of the GRS.

Simon-Miller, Amy A.↗
DOE OSTI2024

Ba₁₋ₓSrₓFeO₃₋ᵧ as an Improved Oxygen Carrier for Chemical Looping Air Separation: A Computational and Experimental Study

Chemical looping air separation (CLAS) is a promising method to generate pure carbon-dioxide from fuel combustion with a pure oxygen stream, which is produced through the capture, and targeted release, of oxygen from the atmosphere using a solid oxide carrier. The performance of this process depends on the redox characteristics of the oxide carrier. Using experimental oxygen-temperature-programmed desorption (TPD) and thermogravimetric analysis (TGA), the study shows that Ba₀․₇₅Sr₀․₂₅FeO₃ has improved oxygen storage capacity (OSC), oxidation, and reduction kinetics over pristine SrFeO₃ at temperatures ranging from 300-500 °C. The redox energetics computed by using first-principles density functional theory (DFT) calculations also depict the measured trend establishing it as an important descriptor of the measured performance. The Ba₁₋ₓSrₓFeO₃₋ᵧ depicts a Sr-substitution and oxygen stoichiometry induced structural phase transition from hexagonal at low temperatures to pseudo-cubic phase with higher OSC up to T=400 °C. Also, the mechanism leading to this structural phase transition is identified by performing electronic and vibrational structural calculations. This presentation was given on March 8, 2024 at the APS March Meeting in Minneapolis, MN.

Acharya, Shree Ram↗
DOE OSTI2020

Materials Data on Ba(CuSe)2 by Materials Project

BaCu2Se2 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 Se2- atoms. All Ba–Se bond lengths are 3.40 Å. Cu1+ is bonded to four equivalent Se2- atoms to form a mixture of edge and corner-sharing CuSe4 tetrahedra. All Cu–Se bond lengths are 2.52 Å. Se2- is bonded in a 8-coordinate geometry to four equivalent Ba2+ and four equivalent Cu1+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ba(AlSi)2 by Materials Project

BaAl2Si2 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 Si4- atoms. All Ba–Si bond lengths are 3.47 Å. Al3+ is bonded to four equivalent Si4- atoms to form a mixture of corner and edge-sharing AlSi4 tetrahedra. All Al–Si bond lengths are 2.56 Å. Si4- is bonded in a 8-coordinate geometry to four equivalent Ba2+ and four equivalent Al3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ba(ZnSb)2 by Materials Project

BaZn2Sb2 crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. Ba2+ is bonded in a 7-coordinate geometry to seven Sb3- atoms. There are a spread of Ba–Sb bond distances ranging from 3.53–3.78 Å. There are two inequivalent Zn2+ sites. In the first Zn2+ site, Zn2+ is bonded to four Sb3- atoms to form a mixture of edge and corner-sharing ZnSb4 tetrahedra. There are a spread of Zn–Sb bond distances ranging from 2.71–2.80 Å. In the second Zn2+ site, Zn2+ is bonded to four Sb3- atoms to form a mixture of edge and corner-sharing ZnSb4 tetrahedra. There are a spread of Zn–Sb bond distances ranging from 2.69–2.85 Å. There are two inequivalent Sb3- sites. In the first Sb3- site, Sb3- is bonded in a 7-coordinate geometry to three equivalent Ba2+ and four Zn2+ atoms. In the second Sb3- site, Sb3- is bonded in a 4-coordinate geometry to four equivalent Ba2+ and four Zn2+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ba(MnAs)2 by Materials Project

BaMn2As2 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 3.39 Å. Mn2+ is bonded to four equivalent As3- atoms to form a mixture of edge and corner-sharing MnAs4 tetrahedra. All Mn–As bond lengths are 2.42 Å. As3- is bonded in a 8-coordinate geometry to four equivalent Ba2+ and four equivalent Mn2+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ba(ScTe2)2 by Materials Project

BaSc2Te4 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 3.52–3.65 Å. There are two inequivalent Sc3+ sites. In the first Sc3+ site, Sc3+ is bonded to six Te2- atoms to form a mixture of corner and edge-sharing ScTe6 octahedra. The corner-sharing octahedra tilt angles range from 47–55°. There are a spread of Sc–Te bond distances ranging from 2.91–2.99 Å. In the second Sc3+ site, Sc3+ is bonded to six Te2- atoms to form a mixture of corner and edge-sharing ScTe6 octahedra. The corner-sharing octahedra tilt angles range from 47–55°. There are a spread of Sc–Te bond distances ranging from 2.93–3.03 Å. There are four inequivalent Te2- sites. In the first Te2- site, Te2- is bonded to two equivalent Ba2+ and three Sc3+ atoms to form a mixture of distorted corner and edge-sharing TeBa2Sc3 trigonal bipyramids. In the second Te2- site, Te2- is bonded in a 5-coordinate geometry to two equivalent Ba2+ and three equivalent Sc3+ atoms. In the third Te2- site, Te2- is bonded in a 5-coordinate geometry to two equivalent Ba2+ and three Sc3+ atoms. In the fourth Te2- site, Te2- is bonded to two equivalent Ba2+ and three equivalent Sc3+ atoms to form a mixture of distorted corner and edge-sharing TeBa2Sc3 square pyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ba(SmTe2)2 by Materials Project

BaSm2Te4 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 3.58–3.79 Å. There are two inequivalent Sm3+ sites. In the first Sm3+ site, Sm3+ is bonded to six Te2- atoms to form a mixture of corner and edge-sharing SmTe6 octahedra. The corner-sharing octahedra tilt angles range from 47–62°. There are a spread of Sm–Te bond distances ranging from 3.11–3.19 Å. In the second Sm3+ site, Sm3+ is bonded to six Te2- atoms to form a mixture of corner and edge-sharing SmTe6 octahedra. The corner-sharing octahedra tilt angles range from 47–62°. There are a spread of Sm–Te bond distances ranging from 3.12–3.18 Å. There are four inequivalent Te2- sites. In the first Te2- site, Te2- is bonded to two equivalent Ba2+ and three Sm3+ atoms to form a mixture of distorted corner and edge-sharing TeBa2Sm3 trigonal bipyramids. In the second Te2- site, Te2- is bonded to two equivalent Ba2+ and three equivalent Sm3+ atoms to form a mixture of distorted corner and edge-sharing TeBa2Sm3 square pyramids. In the third Te2- site, Te2- is bonded in a 5-coordinate geometry to two equivalent Ba2+ and three Sm3+ atoms. In the fourth Te2- site, Te2- is bonded in a 5-coordinate geometry to two equivalent Ba2+ and three equivalent Sm3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ba(YTe2)2 by Materials Project

BaY2Te4 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 Y3+ sites. In the first Y3+ site, Y3+ is bonded to six Te2- atoms to form a mixture of edge and corner-sharing YTe6 octahedra. The corner-sharing octahedra tilt angles range from 47–59°. There are a spread of Y–Te bond distances ranging from 3.07–3.13 Å. In the second Y3+ site, Y3+ is bonded to six Te2- atoms to form a mixture of edge and corner-sharing YTe6 octahedra. The corner-sharing octahedra tilt angles range from 47–59°. There are a spread of Y–Te bond distances ranging from 3.07–3.15 Å. There are four inequivalent Te2- sites. In the first Te2- site, Te2- is bonded to two equivalent Ba2+ and three Y3+ atoms to form a mixture of distorted edge and corner-sharing TeBa2Y3 trigonal bipyramids. In the second Te2- site, Te2- is bonded in a 5-coordinate geometry to two equivalent Ba2+ and three equivalent Y3+ atoms. In the third Te2- site, Te2- is bonded in a 5-coordinate geometry to two equivalent Ba2+ and three Y3+ atoms. In the fourth Te2- site, Te2- is bonded to two equivalent Ba2+ and three equivalent Y3+ atoms to form a mixture of distorted edge and corner-sharing TeBa2Y3 square pyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ba(AgTe)2 by Materials Project

BaAg2Te2 crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. Ba2+ is bonded in a 7-coordinate geometry to seven Te2- atoms. There are a spread of Ba–Te bond distances ranging from 3.50–3.78 Å. There are two inequivalent Ag1+ sites. In the first Ag1+ site, Ag1+ is bonded in a 6-coordinate geometry to two equivalent Ag1+ and four Te2- atoms. Both Ag–Ag bond lengths are 2.94 Å. There are a spread of Ag–Te bond distances ranging from 2.87–2.95 Å. In the second Ag1+ site, Ag1+ is bonded to four Te2- atoms to form a mixture of corner and edge-sharing AgTe4 tetrahedra. There are a spread of Ag–Te bond distances ranging from 2.82–2.96 Å. There are two inequivalent Te2- sites. In the first Te2- site, Te2- is bonded to three equivalent Ba2+ and four Ag1+ atoms to form a mixture of distorted corner and edge-sharing TeBa3Ag4 pentagonal bipyramids. In the second Te2- site, Te2- is bonded in a 8-coordinate geometry to four equivalent Ba2+ and four Ag1+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ba(FeO2)2 by Materials Project

BaFe2O4 crystallizes in the hexagonal P6_322 space group. The structure is three-dimensional. Ba2+ is bonded in a distorted q6 geometry to nine O2- atoms. There are six shorter (2.93 Å) and three longer (3.18 Å) Ba–O bond lengths. Fe3+ is bonded to four O2- atoms to form corner-sharing FeO4 tetrahedra. There is one shorter (1.87 Å) and three longer (1.90 Å) Fe–O bond length. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a linear geometry to three equivalent Ba2+ and two equivalent Fe3+ atoms. In the second O2- site, O2- is bonded in a distorted bent 120 degrees geometry to two equivalent Ba2+ and two equivalent Fe3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ba(MnP)2 by Materials Project

BaMn2P2 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 P3- atoms. All Ba–P bond lengths are 3.35 Å. Mn2+ is bonded to four equivalent P3- atoms to form a mixture of corner and edge-sharing MnP4 tetrahedra. All Mn–P bond lengths are 2.28 Å. P3- is bonded in a 4-coordinate geometry to four equivalent Ba2+ and four equivalent Mn2+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ba(CoAs)2 by Materials Project

BaCo2As2 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 3.43 Å. Co2+ is bonded to four equivalent As3- atoms to form a mixture of edge and corner-sharing CoAs4 tetrahedra. All Co–As bond lengths are 2.33 Å. As3- is bonded in a 8-coordinate geometry to four equivalent Ba2+ and four equivalent Co2+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ba(TeO3)2 by Materials Project

BaTe2O6 crystallizes in the orthorhombic Cmcm space group. The structure is three-dimensional. Ba2+ is bonded in a 10-coordinate geometry to ten O2- atoms. There are a spread of Ba–O bond distances ranging from 2.91–3.07 Å. There are two inequivalent Te5+ sites. In the first Te5+ site, Te5+ is bonded to six O2- atoms to form TeO6 octahedra that share corners with two equivalent TeO6 octahedra and corners with four equivalent TeO5 square pyramids. The corner-sharing octahedral tilt angles are 38°. There is four shorter (1.95 Å) and two longer (1.97 Å) Te–O bond length. In the second Te5+ site, Te5+ is bonded to five O2- atoms to form corner-sharing TeO5 square pyramids. The corner-sharing octahedral tilt angles are 59°. There are one shorter (1.85 Å) and four longer (2.15 Å) Te–O bond lengths. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a 2-coordinate geometry to two equivalent Ba2+ and two Te5+ atoms. In the second O2- site, O2- is bonded in a bent 150 degrees geometry to two equivalent Te5+ atoms. In the third O2- site, O2- is bonded in a distorted single-bond geometry to two equivalent Ba2+ and one Te5+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ba(FeS2)2 by Materials Project

BaFe2S4 crystallizes in the tetragonal I4/m space group. The structure is three-dimensional. Ba2+ is bonded to twelve equivalent S2- atoms to form BaS12 cuboctahedra that share corners with eight equivalent FeS4 tetrahedra, edges with eight equivalent BaS12 cuboctahedra, edges with eight equivalent FeS4 tetrahedra, and faces with two equivalent BaS12 cuboctahedra. There are four shorter (3.30 Å) and eight longer (3.57 Å) Ba–S bond lengths. Fe3+ is bonded to four equivalent S2- atoms to form FeS4 tetrahedra that share corners with four equivalent BaS12 cuboctahedra, edges with four equivalent BaS12 cuboctahedra, and edges with two equivalent FeS4 tetrahedra. All Fe–S bond lengths are 2.14 Å. S2- is bonded in a 2-coordinate geometry to three equivalent Ba2+ and two equivalent Fe3+ atoms.

36 MATERIALS SCIENCE↗