Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “Ta”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 685 records · Page 38
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on Ta2FeO6 by Materials Project

FeTa2O6 is zeta iron carbide-derived structured and crystallizes in the monoclinic P2 space group. The structure is three-dimensional. there are eight inequivalent Ta5+ sites. In the first Ta5+ site, Ta5+ is bonded to six O2- atoms to form TaO6 octahedra that share corners with two equivalent FeO6 octahedra, corners with six TaO6 octahedra, an edgeedge with one TaO6 octahedra, and an edgeedge with one FeO6 octahedra. The corner-sharing octahedra tilt angles range from 36–54°. There are a spread of Ta–O bond distances ranging from 1.95–2.10 Å. In the second Ta5+ site, Ta5+ is bonded to six O2- atoms to form TaO6 octahedra that share corners with four TaO6 octahedra, corners with four FeO6 octahedra, an edgeedge with one TaO6 octahedra, and an edgeedge with one FeO6 octahedra. The corner-sharing octahedra tilt angles range from 36–59°. There are a spread of Ta–O bond distances ranging from 1.87–2.14 Å. In the third Ta5+ site, Ta5+ is bonded to six O2- atoms to form TaO6 octahedra that share corners with four equivalent TaO6 octahedra, corners with four equivalent FeO6 octahedra, an edgeedge with one TaO6 octahedra, and an edgeedge with one FeO6 octahedra. The corner-sharing octahedra tilt angles range from 40–55°. There are two shorter (1.99 Å) and four longer (2.01 Å) Ta–O bond lengths. In the fourth Ta5+ site, Ta5+ is bonded to six O2- atoms to form TaO6 octahedra that share corners with four equivalent TaO6 octahedra, corners with four equivalent FeO6 octahedra, an edgeedge with one TaO6 octahedra, and an edgeedge with one FeO6 octahedra. The corner-sharing octahedra tilt angles range from 40–52°. There are a spread of Ta–O bond distances ranging from 1.95–2.06 Å. In the fifth Ta5+ site, Ta5+ is bonded to six O2- atoms to form TaO6 octahedra that share corners with four equivalent TaO6 octahedra, corners with four equivalent FeO6 octahedra, an edgeedge with one TaO6 octahedra, and an edgeedge with one FeO6 octahedra. The corner-sharing octahedra tilt angles range from 41–55°. There are two shorter (1.99 Å) and four longer (2.01 Å) Ta–O bond lengths. In the sixth Ta5+ site, Ta5+ is bonded to six O2- atoms to form TaO6 octahedra that share corners with four TaO6 octahedra, corners with four FeO6 octahedra, an edgeedge with one TaO6 octahedra, and an edgeedge with one FeO6 octahedra. The corner-sharing octahedra tilt angles range from 36–59°. There are a spread of Ta–O bond distances ranging from 1.87–2.13 Å. In the seventh Ta5+ site, Ta5+ is bonded to six O2- atoms to form TaO6 octahedra that share corners with two equivalent FeO6 octahedra, corners with six TaO6 octahedra, an edgeedge with one TaO6 octahedra, and an edgeedge with one FeO6 octahedra. The corner-sharing octahedra tilt angles range from 36–54°. There are a spread of Ta–O bond distances ranging from 1.95–2.11 Å. In the eighth Ta5+ site, Ta5+ is bonded to six O2- atoms to form TaO6 octahedra that share corners with four equivalent TaO6 octahedra, corners with four equivalent FeO6 octahedra, an edgeedge with one TaO6 octahedra, and an edgeedge with one FeO6 octahedra. The corner-sharing octahedra tilt angles range from 40–52°. There are a spread of Ta–O bond distances ranging from 1.95–2.07 Å. There are four inequivalent Fe2+ sites. In the first Fe2+ site, Fe2+ is bonded to six O2- atoms to form FeO6 octahedra that share corners with two equivalent FeO6 octahedra, corners with six TaO6 octahedra, and edges with two TaO6 octahedra. The corner-sharing octahedra tilt angles range from 40–59°. There are a spread of Fe–O bond distances ranging from 2.05–2.23 Å. In the second Fe2+ site, Fe2+ is bonded to six O2- atoms to form FeO6 octahedra that share corners with eight TaO6 octahedra and edges with two TaO6 octahedra. The corner-sharing octahedra tilt angles range from 50–54°. There are a spread of Fe–O bond distances ranging from 2.16–2.19 Å. In the third Fe2+ site, Fe2+ is bonded to six O2- atoms to form FeO6 octahedra that share corners with two equivalent FeO6 octahedra, corners with six TaO6 octahedra, and edges with two TaO6 octahedra. The corner-sharing octahedra tilt angles range from 40–59°. There are a spread of Fe–O bond distances ranging from 2.05–2.24 Å. In the fourth Fe2+ site, Fe2+ is bonded to six O2- atoms to form FeO6 octahedra that share corners with eight TaO6 octahedra and edges with two TaO6 octahedra. The corner-sharing octahedra tilt angles range from 50–54°. There are a spread of Fe–O bond distances ranging from 2.16–2.19 Å. There are eighteen inequivalent O2- sites. In the first O2- site, O2- is bonded in a 3-coordinate geometry to two Ta5+ and one Fe2+ atom. In the second O2- site, O2- is bonded in a distorted trigonal planar geometry to two Ta5+ and one Fe2+ atom. In the third O2- site, O2- is bonded in a 3-coordinate geometry to one Ta5+ and two Fe2+ atoms. In the fourth O2- site, O2- is bonded in a distorted trigonal planar geometry to two Ta5+ and one Fe2+ atom. In the fifth O2- site, O2- is bonded in a 3-coordinate geometry to two Ta5+ and one Fe2+ atom. In the sixth O2- site, O2- is bonded in a distorted trigonal planar geometry to three Ta5+ atoms. In the seventh O2- site, O2- is bonded in a 3-coordinate geometry to two Ta5+ and one Fe2+ atom. In the eighth O2- site, O2- is bonded in a 3-coordinate geometry to two Ta5+ and one Fe2+ atom. In the ninth O2- site, O2- is bonded in a 3-coordinate geometry to two Ta5+ and one Fe2+ atom. In the tenth O2- site, O2- is bonded in a distorted trigonal planar geometry to two Ta5+ and one Fe2+ atom. In the eleventh O2- site, O2- is bonded in a 3-coordinate geometry to two Ta5+ and one Fe2+ atom. In the twelfth O2- site, O2- is bonded in a 3-coordinate geometry to one Ta5+ and two Fe2+ atoms. In the thirteenth O2- site, O2- is bonded in a 3-coordinate geometry to two Ta5+ and one Fe2+ atom. In the fourteenth O2- site, O2- is bonded in a 3-coordinate geometry to two Ta5+ and one Fe2+ atom. In the fifteenth O2- site, O2- is bonded in a 3-coordinate geometry to two Ta5+ and one Fe2+ atom. In the sixteenth O2- site, O2- is bonded in a 3-coordinate geometry to two Ta5+ and one Fe2+ atom. In the seventeenth O2- site, O2- is bonded in a distorted trigonal planar geometry to three Ta5+ atoms. In the eighteenth O2- site, O2- is bonded in a distorted trigonal planar geometry to two Ta5+ and one Fe2+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Sr3NdTaAl3O12 by Materials Project

Sr3NdTaAl3O12 crystallizes in the monoclinic C2 space group. The structure is three-dimensional. there are four inequivalent Sr sites. In the first Sr site, Sr is bonded to twelve O atoms to form distorted SrO12 cuboctahedra that share corners with four equivalent SrO12 cuboctahedra, a faceface with one NdO12 cuboctahedra, faces with five SrO12 cuboctahedra, faces with two equivalent TaO6 octahedra, and faces with six AlO6 octahedra. There are a spread of Sr–O bond distances ranging from 2.56–3.06 Å. In the second Sr site, Sr is bonded in a 12-coordinate geometry to eleven O atoms. There are a spread of Sr–O bond distances ranging from 2.56–2.83 Å. In the third Sr site, Sr is bonded to twelve O atoms to form distorted SrO12 cuboctahedra that share corners with four equivalent NdO12 cuboctahedra, corners with eight SrO12 cuboctahedra, faces with four equivalent SrO12 cuboctahedra, faces with two equivalent TaO6 octahedra, and faces with six AlO6 octahedra. There are a spread of Sr–O bond distances ranging from 2.59–2.99 Å. In the fourth Sr site, Sr is bonded to twelve O atoms to form distorted SrO12 cuboctahedra that share corners with two equivalent NdO12 cuboctahedra, corners with ten SrO12 cuboctahedra, faces with two equivalent SrO12 cuboctahedra, and faces with eight AlO6 octahedra. There are a spread of Sr–O bond distances ranging from 2.62–3.05 Å. There are two inequivalent Nd sites. In the first Nd site, Nd is bonded in a 12-coordinate geometry to twelve O atoms. There are a spread of Nd–O bond distances ranging from 2.46–3.05 Å. In the second Nd site, Nd is bonded to twelve O atoms to form distorted NdO12 cuboctahedra that share corners with two equivalent NdO12 cuboctahedra, corners with ten SrO12 cuboctahedra, faces with two equivalent SrO12 cuboctahedra, faces with four equivalent TaO6 octahedra, and faces with four AlO6 octahedra. There are a spread of Nd–O bond distances ranging from 2.45–2.90 Å. Ta is bonded to six O atoms to form TaO6 octahedra that share a cornercorner with one TaO6 octahedra, corners with five AlO6 octahedra, faces with two equivalent NdO12 cuboctahedra, and faces with four SrO12 cuboctahedra. The corner-sharing octahedra tilt angles range from 8–17°. There are a spread of Ta–O bond distances ranging from 1.94–2.04 Å. There are three inequivalent Al sites. In the first Al site, Al is bonded to six O atoms to form AlO6 octahedra that share corners with two equivalent TaO6 octahedra, corners with four AlO6 octahedra, a faceface with one NdO12 cuboctahedra, and faces with five SrO12 cuboctahedra. The corner-sharing octahedra tilt angles range from 3–16°. There are a spread of Al–O bond distances ranging from 1.92–1.98 Å. In the second Al site, Al is bonded to six O atoms to form AlO6 octahedra that share corners with two equivalent TaO6 octahedra, corners with four AlO6 octahedra, a faceface with one NdO12 cuboctahedra, and faces with five SrO12 cuboctahedra. The corner-sharing octahedra tilt angles range from 8–18°. There are a spread of Al–O bond distances ranging from 1.90–1.98 Å. In the third Al site, Al is bonded to six O atoms to form AlO6 octahedra that share a cornercorner with one TaO6 octahedra, corners with five AlO6 octahedra, and faces with six SrO12 cuboctahedra. The corner-sharing octahedra tilt angles range from 2–11°. There are a spread of Al–O bond distances ranging from 1.89–1.96 Å. There are fourteen inequivalent O sites. In the first O site, O is bonded in a 2-coordinate geometry to two Sr, two Nd, one Ta, and one Al atom. In the second O site, O is bonded in a 2-coordinate geometry to three Sr, one Nd, one Ta, and one Al atom. In the third O site, O is bonded in a 6-coordinate geometry to three Sr, one Nd, and two Al atoms. In the fourth O site, O is bonded to four Sr and two Al atoms to form distorted OSr4Al2 octahedra that share corners with three OSr4Al2 octahedra and a faceface with one OSr3NdAl2 octahedra. The corner-sharing octahedra tilt angles range from 55–61°. In the fifth O site, O is bonded in a 5-coordinate geometry to three Nd and two equivalent Ta atoms. In the sixth O site, O is bonded in a 2-coordinate geometry to four Sr and two Al atoms. In the seventh O site, O is bonded to three Sr, one Nd, and two equivalent Al atoms to form a mixture of distorted corner and face-sharing OSr3NdAl2 octahedra. The corner-sharing octahedra tilt angles range from 0–61°. In the eighth O site, O is bonded in a 6-coordinate geometry to three Sr, one Nd, one Ta, and one Al atom. In the ninth O site, O is bonded in a distorted linear geometry to four Sr and two Al atoms. In the tenth O site, O is bonded in a 2-coordinate geometry to two Sr, two Nd, one Ta, and one Al atom. In the eleventh O site, O is bonded in a 2-coordinate geometry to three Sr, one Nd, and two Al atoms. In the twelfth O site, O is bonded in a 2-coordinate geometry to four Sr, one Ta, and one Al atom. In the thirteenth O site, O is bonded in a distorted linear geometry to three Sr, one Nd, and two equivalent Al atoms. In the fourteenth O site, O is bonded in a 3-coordinate geometry to one Sr, three Nd, and two equivalent Al atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ta3MnS6 by Materials Project

Ta3MnS6 is Ilmenite-like structured and crystallizes in the hexagonal P6_322 space group. The structure is three-dimensional. there are two inequivalent Ta+3.33+ sites. In the first Ta+3.33+ site, Ta+3.33+ is bonded to six equivalent S2- atoms to form distorted TaS6 pentagonal pyramids that share corners with six equivalent MnS6 octahedra and edges with six equivalent TaS6 pentagonal pyramids. The corner-sharing octahedral tilt angles are 46°. All Ta–S bond lengths are 2.49 Å. In the second Ta+3.33+ site, Ta+3.33+ is bonded to six equivalent S2- atoms to form distorted TaS6 pentagonal pyramids that share corners with three equivalent MnS6 octahedra, edges with six TaS6 pentagonal pyramids, and a faceface with one MnS6 octahedra. The corner-sharing octahedral tilt angles are 47°. There are three shorter (2.47 Å) and three longer (2.51 Å) Ta–S bond lengths. Mn2+ is bonded to six equivalent S2- atoms to form MnS6 octahedra that share corners with twelve TaS6 pentagonal pyramids and faces with two equivalent TaS6 pentagonal pyramids. All Mn–S bond lengths are 2.35 Å. S2- is bonded to three Ta+3.33+ and one Mn2+ atom to form a mixture of distorted edge, face, and corner-sharing STa3Mn trigonal pyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ta2FeO6 by Materials Project

FeTa2O6 is zeta iron carbide-derived structured and crystallizes in the monoclinic P2 space group. The structure is three-dimensional. there are eight inequivalent Ta5+ sites. In the first Ta5+ site, Ta5+ is bonded to six O2- atoms to form TaO6 octahedra that share corners with eight TaO6 octahedra, an edgeedge with one TaO6 octahedra, and an edgeedge with one FeO6 octahedra. The corner-sharing octahedra tilt angles range from 36–52°. There are a spread of Ta–O bond distances ranging from 1.94–2.05 Å. In the second Ta5+ site, Ta5+ is bonded to six O2- atoms to form TaO6 octahedra that share corners with four TaO6 octahedra, corners with four FeO6 octahedra, an edgeedge with one TaO6 octahedra, and an edgeedge with one FeO6 octahedra. The corner-sharing octahedra tilt angles range from 39–53°. There are a spread of Ta–O bond distances ranging from 1.97–2.04 Å. In the third Ta5+ site, Ta5+ is bonded to six O2- atoms to form TaO6 octahedra that share corners with two equivalent FeO6 octahedra, corners with six TaO6 octahedra, an edgeedge with one TaO6 octahedra, and an edgeedge with one FeO6 octahedra. The corner-sharing octahedra tilt angles range from 32–56°. There are a spread of Ta–O bond distances ranging from 1.94–2.11 Å. In the fourth Ta5+ site, Ta5+ is bonded to six O2- atoms to form TaO6 octahedra that share corners with four equivalent TaO6 octahedra, corners with four equivalent FeO6 octahedra, an edgeedge with one TaO6 octahedra, and an edgeedge with one FeO6 octahedra. The corner-sharing octahedra tilt angles range from 41–54°. There are four shorter (2.00 Å) and two longer (2.02 Å) Ta–O bond lengths. In the fifth Ta5+ site, Ta5+ is bonded to six O2- atoms to form TaO6 octahedra that share corners with four TaO6 octahedra, corners with four FeO6 octahedra, an edgeedge with one TaO6 octahedra, and an edgeedge with one FeO6 octahedra. The corner-sharing octahedra tilt angles range from 36–59°. There are a spread of Ta–O bond distances ranging from 1.87–2.12 Å. In the sixth Ta5+ site, Ta5+ is bonded to six O2- atoms to form TaO6 octahedra that share corners with four equivalent TaO6 octahedra, corners with four equivalent FeO6 octahedra, an edgeedge with one TaO6 octahedra, and an edgeedge with one FeO6 octahedra. The corner-sharing octahedra tilt angles range from 41–54°. There are a spread of Ta–O bond distances ranging from 1.99–2.03 Å. In the seventh Ta5+ site, Ta5+ is bonded to six O2- atoms to form TaO6 octahedra that share corners with four TaO6 octahedra, corners with four FeO6 octahedra, an edgeedge with one TaO6 octahedra, and an edgeedge with one FeO6 octahedra. The corner-sharing octahedra tilt angles range from 41–53°. There are a spread of Ta–O bond distances ranging from 1.98–2.03 Å. In the eighth Ta5+ site, Ta5+ is bonded to six O2- atoms to form distorted TaO6 octahedra that share corners with four equivalent TaO6 octahedra, corners with four equivalent FeO6 octahedra, an edgeedge with one TaO6 octahedra, and an edgeedge with one FeO6 octahedra. The corner-sharing octahedra tilt angles range from 32–62°. There are a spread of Ta–O bond distances ranging from 1.86–2.22 Å. There are four inequivalent Fe2+ sites. In the first Fe2+ site, Fe2+ is bonded to six O2- atoms to form FeO6 octahedra that share corners with four equivalent TaO6 octahedra, corners with four equivalent FeO6 octahedra, and edges with two TaO6 octahedra. The corner-sharing octahedra tilt angles range from 40–59°. There are a spread of Fe–O bond distances ranging from 2.04–2.24 Å. In the second Fe2+ site, Fe2+ is bonded to six O2- atoms to form FeO6 octahedra that share corners with eight TaO6 octahedra and edges with two TaO6 octahedra. The corner-sharing octahedra tilt angles range from 50–54°. There are a spread of Fe–O bond distances ranging from 2.12–2.21 Å. In the third Fe2+ site, Fe2+ is bonded to six O2- atoms to form FeO6 octahedra that share corners with two equivalent FeO6 octahedra, corners with six TaO6 octahedra, and edges with two TaO6 octahedra. The corner-sharing octahedra tilt angles range from 38–62°. There are a spread of Fe–O bond distances ranging from 2.03–2.24 Å. In the fourth Fe2+ site, Fe2+ is bonded to six O2- atoms to form FeO6 octahedra that share corners with eight TaO6 octahedra and edges with two TaO6 octahedra. The corner-sharing octahedra tilt angles range from 51–53°. There are two shorter (2.14 Å) and four longer (2.19 Å) Fe–O bond lengths. There are eighteen inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted trigonal planar geometry to two Ta5+ and one Fe2+ atom. In the second O2- site, O2- is bonded in a distorted trigonal planar geometry to two Ta5+ and one Fe2+ atom. In the third O2- site, O2- is bonded in a 3-coordinate geometry to one Ta5+ and two Fe2+ atoms. In the fourth O2- site, O2- is bonded in a 3-coordinate geometry to two Ta5+ and one Fe2+ atom. In the fifth O2- site, O2- is bonded in a 3-coordinate geometry to two Ta5+ and one Fe2+ atom. In the sixth O2- site, O2- is bonded in a 3-coordinate geometry to two Ta5+ and one Fe2+ atom. In the seventh O2- site, O2- is bonded in a 3-coordinate geometry to two Ta5+ and one Fe2+ atom. In the eighth O2- site, O2- is bonded in a 3-coordinate geometry to two Ta5+ and one Fe2+ atom. In the ninth O2- site, O2- is bonded in a distorted trigonal planar geometry to three Ta5+ atoms. In the tenth O2- site, O2- is bonded in a 3-coordinate geometry to one Ta5+ and two Fe2+ atoms. In the eleventh O2- site, O2- is bonded in a 3-coordinate geometry to two Ta5+ and one Fe2+ atom. In the twelfth O2- site, O2- is bonded in a 3-coordinate geometry to two Ta5+ and one Fe2+ atom. In the thirteenth O2- site, O2- is bonded in a distorted trigonal planar geometry to three Ta5+ atoms. In the fourteenth O2- site, O2- is bonded in a 3-coordinate geometry to two Ta5+ and one Fe2+ atom. In the fifteenth O2- site, O2- is bonded in a distorted trigonal planar geometry to two Ta5+ and one Fe2+ atom. In the sixteenth O2- site, O2- is bonded in a trigonal planar geometry to two Ta5+ and one Fe2+ atom. In the seventeenth O2- site, O2- is bonded in a 3-coordinate geometry to two Ta5+ and one Fe2+ atom. In the eighteenth O2- site, O2- is bonded in a 3-coordinate geometry to two Ta5+ and one Fe2+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ta2GaNi3 by Materials Project

Ta2Ni3Ga crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. Ta is bonded in a 12-coordinate geometry to four equivalent Ta, nine equivalent Ni, and three equivalent Ga atoms. There are one shorter (2.96 Å) and three longer (2.98 Å) Ta–Ta bond lengths. There are three shorter (2.77 Å) and six longer (2.87 Å) Ta–Ni bond lengths. All Ta–Ga bond lengths are 2.87 Å. Ni is bonded to six equivalent Ta, four equivalent Ni, and two equivalent Ga atoms to form NiTa6Ga2Ni4 cuboctahedra that share corners with four equivalent GaTa6Ni6 cuboctahedra, corners with fourteen equivalent NiTa6Ga2Ni4 cuboctahedra, edges with six equivalent NiTa6Ga2Ni4 cuboctahedra, faces with six equivalent GaTa6Ni6 cuboctahedra, and faces with twelve equivalent NiTa6Ga2Ni4 cuboctahedra. There are two shorter (2.38 Å) and two longer (2.53 Å) Ni–Ni bond lengths. Both Ni–Ga bond lengths are 2.43 Å. Ga is bonded to six equivalent Ta and six equivalent Ni atoms to form GaTa6Ni6 cuboctahedra that share corners with twelve equivalent NiTa6Ga2Ni4 cuboctahedra, edges with six equivalent GaTa6Ni6 cuboctahedra, faces with two equivalent GaTa6Ni6 cuboctahedra, and faces with eighteen equivalent NiTa6Ga2Ni4 cuboctahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Two-Dimensional Tantalum Carbo-Selenide for Hydrogen Evolution

Herein, we report the synthesis of two-dimensional Ta 2 Se 2 C (2D-Ta 2 Se 2 C) nanosheets using electrochemical lithiation in multilayer Ta 2 Se 2 C followed by sonication in deionized water. Multilayer Ta 2 Se 2 C was obtained via solid-state synthesis of Fe x Ta 2 Se 2 C followed by chemical etching of Fe. 2D-Ta 2 Se 2 C exhibited promising electrocatalytic activity for the hydrogen evolution reaction from water compared to multilayer Ta 2 Se 2 C and 2D-TaSe 2 . 2D-Ta 2 Se 2 C showed an overpotential at 10 mA·cm -2 (η 10 ) of 264 mV, a Tafel slope of 91 mV·dec -1 , and an electrochemically active surface area of 17.61 m ECSA 2 ·g catalyst -1 . The high performance could be attributed to the large surface area of single sheets which hence maximizes the number of exposed catalytic sites and increased density of vacancies, observed with transmission electron microscopy, during synthesis and processing.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Two-level systems in nucleated and non-nucleated epitaxial alpha-tantalum films

Building usefully coherent superconducting quantum processors depends on reducing losses in their constituent materials. Tantalum, like niobium, has proven utility as the primary superconducting layer within highly coherent qubits. However, unlike Nb, high temperatures are typically used to stabilize the desirable body-centered-cubic phase, α-Ta, during thin film deposition. It has long been known that a thin Nb layer permits the room-temperature nucleation of α-Ta, but here we observe the epitaxial process and present few-photon microwave loss measurements in Nb-nucleated Ta films. We compare resonators patterned from Ta films grown at high temperature (500 °C) and films nucleated at room temperature, in order to understand the impact of the crystalline order on quantum coherence. In both cases, films grew with Al 2 O 3 (001) ∥ Ta (110), indicating that the epitaxial orientation is independent of temperature and is preserved across the Nb/Ta interface. We use conventional low-power spectroscopy to measure two level system (TLS) loss as well as an electric-field bias technique to measure the effective dipole moments of TLS in the surfaces of resonators. In our measurements, Nb-nucleated Ta resonators had greater loss tangent (1.5 ± 0.1 × 10 -5 ) than non-nucleated (5 ± 1× 10 -6 ) in approximate proportion to defect densities as characterized by x-ray diffraction (0.27° vs 0.18° [110] reflection width) and electron microscopy (30 vs 70 nm domain size). Furthermore, the dependence of the loss tangent on domain size indicates that the development of more ordered Ta films is likely to lead to improvements in qubit coherence times. Moreover, low-temperature α-Ta epitaxy may enable the growth of microstate-free heterostructures, which would not withstand high temperature processing.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2025

Interface-sensitive microwave loss in superconducting tantalum films sputtered on c-plane sapphire

Quantum coherence in superconducting circuits has increased steadily over the last decades because of a growing understanding of the various loss mechanisms. Recently, tantalum (Ta) emerged as a promising material to address microscopic sources of loss found on niobium (Nb) or aluminum (Al) surfaces. However, the effects of film and interface microstructure on low-temperature microwave loss are still not well understood. Here, in this study, we present a systematic study of the structural and electrical properties of Ta and Nb films sputtered on c-plane sapphire at varying growth temperatures. As growth temperature was increased, our results show that the onset of epitaxial growth of α -phase Ta correlates with lower Ta surface roughness, higher critical temperature, and higher residual resistivity ratio, but surprisingly also correlates with a significant increase in loss at microwave frequency. Notably, this high level of loss is not observed in Nb films prepared in the same way and having very similar structure. By experimentally controlling the surface on which the Ta film is nucleated, we determine that the source of loss was only present in samples having an epitaxial Ta/sapphire interface and show that it was apparently mitigated by either growing a thin, epitaxial Nb interlayer between the Ta film and the substrate or by intentionally treating, and effectively damaging, the sapphire surface with an in situ argon plasma before Ta growth. In addition to elucidating this interfacial microwave loss, this work provides adequate process details to aid reproducible growth of low-loss Ta films across fabrication facilities.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2023

2022 Results for Avian Monitoring of Inorganic Elements and Organic Chemical Concentrations in Passerine Eggs and Nestlings Collected from Technical Area 16 Burn Grounds, Technical Area 36 Minie, and Technical Area 39 Point 6 at Los Alamos National Laboratory

In 2022, nonviable avian eggs and one nestling were opportunistically collected at Los Alamos National Laboratory (LANL) near open detonation sites located at Technical Area (TA) 16 burn grounds, TA-36 Minie, and TA-39 Point 6. Samples were evaluated for inorganic elements (mostly metals) or per- and polyfluoroalkyl substances (PFAS). Three western bluebird (Sialia mexicana) egg samples were collected from TA-16 burn grounds. One deceased mountain bluebird (Sialia currucoides) nestling sample was collected from TA-36 Minie. One ash-throated flycatcher (Myiarchus cinerascens) egg sample was collected from TA-39 Point 6. Concentrations of inorganic elements (i.e., mostly metals) observed in this study were compared with the regional statistical reference level (RSRL), which is the upper-level bounds of background concentrations (mean + three standard deviations = 99% confidence interval). Several inorganic elements were not detected in avian eggs. All of the inorganic elements that were detected were below the RSRL and the lowest observable adverse effect level (LOAEL), when available. No PFAS compounds were detected in the mountain bluebird nestling sample collected from TA-36, and the majority of PFAS compounds were not detected in the western bluebird egg sample from TA-16. These data suggest that inorganic element and PFAS concentrations in eggs and nestlings are not of ecological concern. More data are needed to make a robust assessment and to evaluate trends over time.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2025

2024 Results for Avian Monitoring at the Technical Area 36 Minie Site, Technical Area 39 Point 6, Technical Area 16 Burn Ground, and DARHT at Los Alamos National Laboratory

Los Alamos National Laboratory (LANL) biological subject matter experts in the Environmental Protection and Compliance Division initiated a multi-year program in 2013 to monitor avifauna (birds) at two open detonation sites and one open burn site on LANL property. Additional monitoring began in 2017 at a third firing site, the Dual-Axis Radiographic Hydrodynamic Test (DARHT) Facility. In this annual report, we compare monitoring results from these efforts among years to identify and evaluate firing and open burn site impacts on the local bird community. The objectives of this study are • to determine whether LANL operations impact bird abundance, species richness, or diversity; • to examine occupancy and nest success of secondary-cavity nesting birds that use nest boxes; and • to examine chemical concentrations (such as radionuclides, inorganic elements, and/or organic compounds) in nonviable eggs and deceased nestlings that are collected opportunistically with the upper-level bounds of background concentrations, when available. During May through July 2024, LANL biologists completed multiple avian point count surveys at each of the following treatment sites: • Technical Area (TA) 36 Minie Site, • TA-39 Point 6, • TA-16 Burn Ground, and • DARHT. We recorded a total of 1,088 birds that represented 65 species at the four treatment sites and compared these results with data from their associated control sites. In 2024, abundance and species richness at treatment and control sites continued to trend similarly from year to year, with minor random deviations expected from bird communities. Species richness at firing sites differed little from the previous year’s values. Two new bird species were observed at the firing sites—cedar waxwing (Bombycilla cedrorum) and pinyon jay (Gymnorhinus cyanocephalus). Shannon diversity values at TA-36 Minie Site, TA-39, and DARHT were statistically higher than one or more of their associated controls. Annual species diversity at treatment sites was high in 2024 across all firing sites relative to similar habitat control sites. We also monitored avian nest boxes to compare occupancy and nest success data from nest boxes at treatment sites with the overall avian nest box monitoring network and against a subset of relevant control sites. Nest box success has decreased at both treatment and control sites since monitoring began, suggesting that overlapping climatic factors are responsible for patterns of declining nest success. In 2024, nonviable avian eggs and one nestling were opportunistically collected at Bandelier National Monument, TA-16 Burn Ground, TA-36 Minie, TA-39 Point 6, and DARHT. All egg samples and the one nestling sample were evaluated for per- and polyfluoroalkyl substances, which were detected from all locations, including the control site at Bandelier National Monument. Overall results from 2024 continue to suggest that operations at the four treatment sites are not negatively impacting bird populations. This long-term project will continue to monitor for any changes over time.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2023

Experiments to Measure the Effect of Tantalum on Critical Systems

Sandia National Laboratories (SNL) and Oak Ridge National Laboratory (ORNL) collaborated to develop a capability to test the epithermal/intermediate cross sections of materials at the SNL critical experiment facility using the Seven Percent Critical Experiment (7uPCX) fuel. As a result, a new set of critical experiments has been designed to target the epithermal cross sections of tantalum (Ta) and is scheduled to be performed at SNL in 2023. These critical experiments will be evaluated for inclusion in the 2024 edition of the International Criticality Safety Benchmark Evaluation Project (ICSBEP) Handbook. The focus of these critical experiments is to measure the effects of Ta on the critical array size. The critical array size will be determined by an approach-to-critical experiment with the number of fuel rods in the array as a free parameter. The core configurations are designed to optimize the reactivity worth of Ta and the overall percentage of Ta absorption rates in the epithermal/intermediate energy range (0.625 eV – 100 keV). The baseline core configuration includes 7uPCX fuel rods set at a triangular pitch of 1.016 cm and a central dry test region that utilizes a cadmium liner for filtering out thermal neutrons. The central test region has locations for 85 Ta rods set at a triangular pitch of 0.813 cm. The Ta reactivity worth for the case with 85 Ta rods is approximately 2.55%, with the percentage of Ta absorption rates within the intermediate energy range at nearly 90%.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2020

Materials Data on TaBe12 by Materials Project

Be12Ta crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. there are three inequivalent Be sites. In the first Be site, Be is bonded in a 10-coordinate geometry to nine Be and one Ta atom. There are a spread of Be–Be bond distances ranging from 2.15–2.34 Å. The Be–Ta bond length is 2.57 Å. In the second Be site, Be is bonded to ten Be and two equivalent Ta atoms to form a mixture of distorted corner, edge, and face-sharing BeTa2Be10 cuboctahedra. There are two shorter (2.11 Å) and four longer (2.12 Å) Be–Be bond lengths. Both Be–Ta bond lengths are 2.79 Å. In the third Be site, Be is bonded in a distorted q6 geometry to ten Be and two equivalent Ta atoms. Both Be–Be bond lengths are 2.23 Å. Both Be–Ta bond lengths are 2.63 Å. Ta is bonded in a 12-coordinate geometry to twenty Be atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on TaMn2 by Materials Project

TaMn2 is Hexagonal Laves structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. Ta is bonded in a 12-coordinate geometry to four equivalent Ta and twelve Mn atoms. All Ta–Ta bond lengths are 2.95 Å. All Ta–Mn bond lengths are 2.82 Å. There are two inequivalent Mn sites. In the first Mn site, Mn is bonded to six equivalent Ta and six equivalent Mn atoms to form a mixture of corner, edge, and face-sharing MnTa6Mn6 cuboctahedra. All Mn–Mn bond lengths are 2.44 Å. In the second Mn site, Mn is bonded to six equivalent Ta and six Mn atoms to form a mixture of corner, edge, and face-sharing MnTa6Mn6 cuboctahedra. There are two shorter (2.33 Å) and two longer (2.48 Å) Mn–Mn bond lengths.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ta3Al2CoC by Materials Project

Ta3Al2CoC crystallizes in the cubic Fd-3m space group. The structure is three-dimensional. Ta is bonded in a distorted bent 150 degrees geometry to two equivalent Co, four equivalent Al, and two equivalent C atoms. Both Ta–Co bond lengths are 2.98 Å. There are two shorter (2.77 Å) and two longer (2.98 Å) Ta–Al bond lengths. Both Ta–C bond lengths are 2.18 Å. Co is bonded to six equivalent Ta and six equivalent Al atoms to form CoTa6Al6 cuboctahedra that share edges with six equivalent CTa6 octahedra and faces with six equivalent CoTa6Al6 cuboctahedra. All Co–Al bond lengths are 2.50 Å. Al is bonded in a 12-coordinate geometry to six equivalent Ta, three equivalent Co, and three equivalent Al atoms. All Al–Al bond lengths are 2.69 Å. C is bonded to six equivalent Ta atoms to form CTa6 octahedra that share corners with six equivalent CTa6 octahedra and edges with six equivalent CoTa6Al6 cuboctahedra. The corner-sharing octahedral tilt angles are 40°.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on TaSe2 by Materials Project

TaSe2 is trigonal omega-like structured and crystallizes in the triclinic P-1 space group. The structure is two-dimensional and consists of one TaSe2 sheet oriented in the (1, 1, 1) direction. there are seven inequivalent Ta4+ sites. In the first Ta4+ site, Ta4+ is bonded to six Se2- atoms to form edge-sharing TaSe6 octahedra. All Ta–Se bond lengths are 2.66 Å. In the second Ta4+ site, Ta4+ is bonded to six Se2- atoms to form edge-sharing TaSe6 octahedra. There are a spread of Ta–Se bond distances ranging from 2.56–2.73 Å. In the third Ta4+ site, Ta4+ is bonded to six Se2- atoms to form edge-sharing TaSe6 octahedra. There are a spread of Ta–Se bond distances ranging from 2.56–2.73 Å. In the fourth Ta4+ site, Ta4+ is bonded to six Se2- atoms to form edge-sharing TaSe6 octahedra. There are a spread of Ta–Se bond distances ranging from 2.56–2.73 Å. In the fifth Ta4+ site, Ta4+ is bonded to six Se2- atoms to form edge-sharing TaSe6 octahedra. There are a spread of Ta–Se bond distances ranging from 2.48–2.77 Å. In the sixth Ta4+ site, Ta4+ is bonded to six Se2- atoms to form edge-sharing TaSe6 octahedra. There are a spread of Ta–Se bond distances ranging from 2.48–2.76 Å. In the seventh Ta4+ site, Ta4+ is bonded to six Se2- atoms to form edge-sharing TaSe6 octahedra. There are a spread of Ta–Se bond distances ranging from 2.48–2.76 Å. There are thirteen inequivalent Se2- sites. In the first Se2- site, Se2- is bonded in a 3-coordinate geometry to three Ta4+ atoms. In the second Se2- site, Se2- is bonded in a 3-coordinate geometry to three Ta4+ atoms. In the third Se2- site, Se2- is bonded in a distorted T-shaped geometry to three Ta4+ atoms. In the fourth Se2- site, Se2- is bonded in a 3-coordinate geometry to three Ta4+ atoms. In the fifth Se2- site, Se2- is bonded in a 3-coordinate geometry to three Ta4+ atoms. In the sixth Se2- site, Se2- is bonded in a 3-coordinate geometry to three Ta4+ atoms. In the seventh Se2- site, Se2- is bonded in a 3-coordinate geometry to three Ta4+ atoms. In the eighth Se2- site, Se2- is bonded in a 3-coordinate geometry to three Ta4+ atoms. In the ninth Se2- site, Se2- is bonded in a 3-coordinate geometry to three Ta4+ atoms. In the tenth Se2- site, Se2- is bonded in a 3-coordinate geometry to three Ta4+ atoms. In the eleventh Se2- site, Se2- is bonded in a 3-coordinate geometry to three Ta4+ atoms. In the twelfth Se2- site, Se2- is bonded in a 3-coordinate geometry to three Ta4+ atoms. In the thirteenth Se2- site, Se2- is bonded in a 3-coordinate geometry to three Ta4+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on TaSn2 by Materials Project

TaSn2 is Khatyrkite-like structured and crystallizes in the orthorhombic Fddd space group. The structure is three-dimensional. Ta is bonded in a 10-coordinate geometry to two equivalent Ta and eight Sn atoms. Both Ta–Ta bond lengths are 2.86 Å. There are a spread of Ta–Sn bond distances ranging from 2.89–2.99 Å. There are two inequivalent Sn sites. In the first Sn site, Sn is bonded in a 4-coordinate geometry to four equivalent Ta atoms. In the second Sn site, Sn is bonded in a 4-coordinate geometry to four equivalent Ta atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on TaFe2 by Materials Project

TaFe2 is Hexagonal Laves structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. Ta is bonded in a 12-coordinate geometry to four equivalent Ta and twelve Fe atoms. There are one shorter (2.91 Å) and three longer (2.95 Å) Ta–Ta bond lengths. There are a spread of Ta–Fe bond distances ranging from 2.80–2.84 Å. There are two inequivalent Fe sites. In the first Fe site, Fe is bonded to six equivalent Ta and six equivalent Fe atoms to form a mixture of edge, face, and corner-sharing FeTa6Fe6 cuboctahedra. All Fe–Fe bond lengths are 2.42 Å. In the second Fe site, Fe is bonded to six equivalent Ta and six Fe atoms to form a mixture of edge, face, and corner-sharing FeTa6Fe6 cuboctahedra. There are two shorter (2.37 Å) and two longer (2.41 Å) Fe–Fe bond lengths.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on TaCo2 by Materials Project

Co2Ta is Hexagonal Laves structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. Ta is bonded in a 12-coordinate geometry to four equivalent Ta and twelve Co atoms. There are one shorter (2.87 Å) and three longer (2.93 Å) Ta–Ta bond lengths. There are a spread of Ta–Co bond distances ranging from 2.78–2.80 Å. There are two inequivalent Co sites. In the first Co site, Co is bonded to six equivalent Ta and six equivalent Co atoms to form a mixture of corner, edge, and face-sharing CoTa6Co6 cuboctahedra. All Co–Co bond lengths are 2.38 Å. In the second Co site, Co is bonded to six equivalent Ta and six Co atoms to form a mixture of corner, edge, and face-sharing CoTa6Co6 cuboctahedra. There are two shorter (2.36 Å) and two longer (2.41 Å) Co–Co bond lengths.

36 MATERIALS SCIENCE↗