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At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

On the Sintering Behavior of Nb2O5 and Ta2O5 Mixed Oxide Powders

A mixed oxide system consisting of Nb2O5 and Ta2O5, was subjected to annealing in air/hydrogen up to 950 °C for 1–4 h to study its sintering behavior. The thermogravimetric–differential scanning calorimetry (TGA–DSC) thermograms indicated the formation of multiple endothermic peaks at temperatures higher than 925 °C. Subsequently, a 30% Ta2O5 and 70% Nb2O5 (mol%) pellet resulted in good sintering behavior at both 900 and 950 °C. The scanning electron microscope (SEM) images corroborated these observations with necking and particle coarsening. The sintered pellets contained a 20.4 and 20.8% mixed oxide (Nb4Ta2O15) phase, along with Ta2O5 and Nb2O5, at both 900 and 950 °C, indicating the possibility of the formation of a solid solution phase. In situ high-temperature X-ray diffraction (XRD) scans also confirmed the formation of the ternary oxide phase at 6 and 19.8% at 890 and 950 °C, respectively. The Hume–Rothery rules could explain the good sintering behavior of the Ta2O5 and Nb2O5 mixed oxides. An oxide composition of 30% Ta2O5 and 70% Nb2O5 (mol%) and a sintering temperature of 950 °C appeared adequate for fabricating well-sintered oxide precursors for subsequent electrochemical polarization studies in fused salts.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ta2O5 by Materials Project

Ta2O5 crystallizes in the monoclinic Cm space group. The structure is two-dimensional and consists of two Ta2O5 sheets oriented in the (1, 0, 0) direction. there are two inequivalent Ta5+ sites. In the first Ta5+ site, Ta5+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Ta–O bond distances ranging from 1.73–2.15 Å. In the second Ta5+ site, Ta5+ is bonded to six O2- atoms to form edge-sharing TaO6 octahedra. There are a spread of Ta–O bond distances ranging from 1.96–2.08 Å. There are five inequivalent O2- sites. In the first O2- site, O2- is bonded in a 3-coordinate geometry to three Ta5+ atoms. In the second O2- site, O2- is bonded in a trigonal non-coplanar geometry to three Ta5+ atoms. In the third O2- site, O2- is bonded in a water-like geometry to two equivalent Ta5+ atoms. In the fourth O2- site, O2- is bonded in a trigonal non-coplanar geometry to three Ta5+ atoms. In the fifth O2- site, O2- is bonded in a single-bond geometry to one Ta5+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ta2O5 by Materials Project

Ta2O5 crystallizes in the monoclinic C2/c space group. The structure is three-dimensional. Ta5+ is bonded to six O2- atoms to form a mixture of edge and corner-sharing TaO6 octahedra. The corner-sharing octahedra tilt angles range from 27–55°. There are a spread of Ta–O bond distances ranging from 1.85–2.17 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted trigonal planar geometry to three equivalent Ta5+ atoms. In the second O2- site, O2- is bonded in a bent 150 degrees geometry to two equivalent Ta5+ atoms. In the third O2- site, O2- is bonded in a bent 150 degrees geometry to two equivalent Ta5+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ta2O5 by Materials Project

Ta2O5 crystallizes in the orthorhombic Pmmm space group. The structure is three-dimensional. there are two inequivalent Ta5+ sites. In the first Ta5+ site, Ta5+ is bonded to six O2- atoms to form a mixture of edge and corner-sharing TaO6 octahedra. The corner-sharing octahedra tilt angles range from 0–58°. There are two shorter (1.95 Å) and four longer (2.19 Å) Ta–O bond lengths. In the second Ta5+ site, Ta5+ is bonded to six O2- atoms to form corner-sharing TaO6 octahedra. The corner-sharing octahedra tilt angles range from 0–58°. There are a spread of Ta–O bond distances ranging from 1.85–2.09 Å. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a linear geometry to two equivalent Ta5+ atoms. In the second O2- site, O2- is bonded in a trigonal planar geometry to three Ta5+ atoms. In the third O2- site, O2- is bonded in a linear geometry to two equivalent Ta5+ atoms. In the fourth O2- site, O2- is bonded in a linear geometry to two equivalent Ta5+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ta2O5 by Materials Project

Ta2O5 crystallizes in the monoclinic C2 space group. The structure is three-dimensional. Ta5+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of Ta–O bond distances ranging from 1.90–2.40 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a 2-coordinate geometry to three equivalent Ta5+ atoms. In the second O2- site, O2- is bonded in a water-like geometry to two equivalent Ta5+ atoms. In the third O2- site, O2- is bonded in a 4-coordinate geometry to four equivalent Ta5+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ta2O5 by Materials Project

Ta2O5 crystallizes in the orthorhombic Pbam space group. The structure is three-dimensional. Ta5+ is bonded to five O2- atoms to form distorted corner-sharing TaO5 trigonal bipyramids. There are a spread of Ta–O bond distances ranging from 1.83–2.08 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a bent 150 degrees geometry to two equivalent Ta5+ atoms. In the second O2- site, O2- is bonded in a bent 150 degrees geometry to two equivalent Ta5+ atoms. In the third O2- site, O2- is bonded in a linear geometry to two equivalent Ta5+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ta2O5 by Materials Project

Ta2O5 crystallizes in the orthorhombic Pmmn space group. The structure is three-dimensional. Ta5+ is bonded to six O2- atoms to form a mixture of corner and edge-sharing TaO6 octahedra. The corner-sharing octahedra tilt angles range from 1–29°. There are a spread of Ta–O bond distances ranging from 1.86–2.22 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a linear geometry to two equivalent Ta5+ atoms. In the second O2- site, O2- is bonded in a linear geometry to two equivalent Ta5+ atoms. In the third O2- site, O2- is bonded in a 3-coordinate geometry to three equivalent Ta5+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ta2O5 by Materials Project

Ta2O5 crystallizes in the monoclinic C2 space group. The structure is three-dimensional. Ta5+ is bonded to five O2- atoms to form a mixture of edge and corner-sharing TaO5 trigonal bipyramids. There are a spread of Ta–O bond distances ranging from 1.87–2.08 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a linear geometry to two equivalent Ta5+ atoms. In the second O2- site, O2- is bonded in a linear geometry to two equivalent Ta5+ atoms. In the third O2- site, O2- is bonded in a water-like geometry to two equivalent Ta5+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ta2O5 by Materials Project

Ta2O5 crystallizes in the monoclinic C2/m space group. The structure is three-dimensional. there are three inequivalent Ta5+ sites. In the first Ta5+ site, Ta5+ is bonded to six O2- atoms to form a mixture of edge and corner-sharing TaO6 octahedra. The corner-sharing octahedra tilt angles range from 0–35°. There are a spread of Ta–O bond distances ranging from 1.92–2.23 Å. In the second Ta5+ site, Ta5+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of Ta–O bond distances ranging from 1.91–2.56 Å. In the third Ta5+ site, Ta5+ is bonded to six O2- atoms to form a mixture of distorted edge and corner-sharing TaO6 octahedra. The corner-sharing octahedra tilt angles range from 13–32°. There are a spread of Ta–O bond distances ranging from 1.93–2.17 Å. There are eight inequivalent O2- sites. In the first O2- site, O2- is bonded in a linear geometry to two equivalent Ta5+ atoms. In the second O2- site, O2- is bonded in a bent 150 degrees geometry to two equivalent Ta5+ atoms. In the third O2- site, O2- is bonded in a 3-coordinate geometry to three Ta5+ atoms. In the fourth O2- site, O2- is bonded in a trigonal planar geometry to three Ta5+ atoms. In the fifth O2- site, O2- is bonded in a 3-coordinate geometry to three Ta5+ atoms. In the sixth O2- site, O2- is bonded in a distorted linear geometry to three Ta5+ atoms. In the seventh O2- site, O2- is bonded in a linear geometry to two equivalent Ta5+ atoms. In the eighth O2- site, O2- is bonded in a linear geometry to two equivalent Ta5+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ta2O5 by Materials Project

Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ta2Bi2O9 by Materials Project

Bi2Ta2O9 crystallizes in the triclinic P-1 space group. The structure is two-dimensional and consists of one BiO2 sheet oriented in the (0, 0, 1) direction and one Ta2O5 sheet oriented in the (0, 0, 1) direction. In the BiO2 sheet, Bi4+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Bi–O bond distances ranging from 2.30–2.87 Å. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a 4-coordinate geometry to four equivalent Bi4+ atoms. In the second O2- site, O2- is bonded to four equivalent Bi4+ atoms to form a mixture of edge and corner-sharing OBi4 tetrahedra. In the Ta2O5 sheet, Ta5+ is bonded to five O2- atoms to form distorted corner-sharing TaO5 trigonal bipyramids. There is one shorter (1.90 Å) and four longer (1.94 Å) Ta–O bond length. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a linear geometry to two equivalent Ta5+ atoms. In the second O2- site, O2- is bonded in a bent 150 degrees geometry to two equivalent Ta5+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Photonic near infrared heater

A multilayer photonic stack comprising a lower plurality of alternating layers comprising at least A and B and an upper plurality of alternating layers comprising at least C and D, layer A comprises at least one of Al, Au, W, Ag, Ni, Ti, Pt, and Cr, layer B comprises at least one of Al2O3, AlN, MgO, SiO2, TiO2, Si3N4, MgF2, Ta2O5, SiC, Si, Ge, and Indium Tin Oxide (ITO), and layers C and D comprise at least one of Al2O3, AlN, MgO, SiO2, TiO2, Si3N4, MgF2, Ta2O5, SiC, Si, Ge, and Indium Tin Oxide (ITO).

Prasher, Ravi Shankar↗
DOE OSTI2025

Comparison of Nb and Ta Pentoxide Loss Tangents for Superconducting Quantum Devices

Superconducting transmon qubits are commonly made with thin-film Nb wiring, but recent studies have shown increased performance with Ta wiring. In this work, we compare the resonator-induced single photon, millikelvin dielectric loss for pentoxides of Nb (Nb2O5) and Ta (Ta2O5) in order to further understand limiting losses in qubits. Nb and Ta pentoxides of three thicknesses are deposited via pulsed laser deposition onto identical coplanar waveguide resonators. The two-level system (TLS) loss in Nb2O5 is determined to be about 30% higher than that of Ta2O5. This work indicates that qubits with Nb wiring are affected by higher loss arising from the native pentoxide itself, likely in addition to the presence of suboxides, which are largely absent in Ta.

Goronzy, D. P. [Northwestern U.]↗
DOE OSTI2023

Targeting Oxide Concentration in Tantalum Oxide-Fluoride Anions

The design of both molecular and non-molecular solid materials with specific properties fundamentally relies on the controlled synthesis of crystals with desired functional groups, bonding motifs, polarity, chirality, and more. To this end, fluoride and oxide-fluoride anions have been utilized as basic building units (BBUs) in the synthesis of noncentrosymmetric racemic materials for their ability to create polar axes that facilitate the breaking of an inversion center as demonstrated in a series of compounds with [MF6]2- anions (M = Ti, Zr, Hf). Targeting an analog with a [TaOF5]2- anion, the phase space of (CuO, Ta2O5)/bpy/HF(aq)/H2O (bpy = 2,2′-bipyridine) was investigated and three new compounds with Cu-bpy cations and Ta-fluoride or Ta-oxyfluoride anions were synthesized: [Cu(bpy)2][TaF6], [Cu(bpy)2][Ta2OF10], and [Cu(bpy)F(H2O)2]2[TaF7]∙H2O with the anions [TaF6]-, [Ta2OF10]2-, and [TaF7]2-, respectively. The formation of these anions was found to be a product of both the concentration of hydrofluoric acid in solution and the ratio of metal-oxide starting materials to ligand. This work contributes to the understanding of mixed anion formation in the solid state.

Kamp, Kendall R.↗
DOE OSTI2024

Trace Element Control in Master Alloys and Impact of Feedstock Purity on a Ta-containing Steel during Electroslag Remelting

Advanced materials design often leads to new complex compositions that can bring challenges to manufacturing processes. Melt processing of a novel alloy with a tight chemistry range revealed a 25% Ta loss after manufacturing. Vacuum induction melting (VIM) and electroslag remelting (ESR) were performed using industry practices at a laboratory scale and the loss occurred from the VIM electrode to the ESR ingot. Several tools were used for characterization, including combustion analysis, scanning electron microscopy, and electron probe microanalysis for observation of the precipitate and inclusion phases. Additionally, computational modeling of the ESR process was performed to predict macrosegregation and inclusion travel. It was found that a significant amount of Ta2O5 inclusions formed during VIM and were transferred to the slag during ESR. This led to a 95% decrease in density of inclusions explaining to Ta loss. Pathways to better control advanced alloy chemistries during melt processing will be discussed.

Detrois, Martin↗
DOE OSTI2025

Chemical Analysis of Tantalum Thin Films compared to Niobium Thin Films using SIMS and XPS

Superconducting qubits are a leading platform for quantum computation. These circuits are typically made from superconducting materials like aluminum or niobium. However, the amorphous niobium oxide and aluminum oxide on the surface of these circuits introduce considerable RF loss due to the presence of two-level systems (TLS), which limits the maximum coherence times T1 to ~100 μs. Capping the niobium qubits with a tantalum layer leads to a 3- 5x improvement [Bal et al., 2024]. But even in this case, tantalum forms an amorphous surface oxide that introduces loss. In an effort to devise strategies to eliminate the presence of this oxide, we present a comprehensive study on the nature of Ta oxide using x-ray photoemission spectroscopy (XPS) and secondary ion mass spectrometry (ToF-SIMS) as a function of heat treatment. The thin films were annealed in ultra-high vacuum conditions and analyzed in situ to characterize the composition and evolution of the native tantalum oxide layer and oxide-metal interface. Our analysis reveals two critical differences between tantalum and niobium oxides: Nb2O5 completely dissolves at 400°C, while Ta2O5 persists even at 800°C. Additionally, tantalum oxide contains only a single suboxide (TaO), in contrast to niobium's two suboxides (NbO and NbO2). The suboxide of tantalum contributes minimally to the total oxide content and shows a relative increase with temperature. Understanding the oxide’s behavior will open new pathways for optimizing coherence times in tantalum qubits.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2022

Synthesis and Ultrahigh Pressure Compression of High-Entropy Boride (Hf0.2Mo0.2Nb0.2Ta0.2Zr0.2)B2 to 220 GPa

The high-entropy boride (Hf0.2Mo0.2Nb0.2Ta0.2Zr0.2)B2 material was synthesized under high-pressures and high-temperatures in a large-volume Paris-Edinburgh (PE) press from a ball-milled powder mix of HfO2, MoO3, Nb2O5, Ta2O5, ZrO2, carbon black, and boron carbide. The transformation process was monitored in situ by energy-dispersive x-ray diffraction with conversion starting at 1100 °C and completed by 2000 °C with the formation of a single hexagonal AlB2-type phase. The synthesized sample was recovered, powdered, and mixed with platinum pressure marker and studied under high pressure by angle-dispersive x-ray diffraction in a diamond anvil cell. The hexagonal AlB2-type phase of (Hf0.2Mo0.2Nb0.2Ta0.2Zr0.2)B2 was found to be stable up to the highest pressure of 220 GPa reached in this study (volume compression V/V0 = 0.70). The third order Birch-Murnaghan equation of state fit to the high-pressure data up to 220 GPa results in an ambient pressure unit cell volume V0=28.16±0.04 Å3, bulk modulusKo = 407 ± 6 GPa, pressure derivative of bulk-modulus K0′ = 2.73 ± 0.045 GPa. Our study indicates that this high-entropy boride (Hf0.2Mo0.2Nb0.2Ta0.2Zr0.2)B2 material is stable to ultrahigh pressures and temperatures and exhibit high bulk modulus similar to other incompressible transition metal borides like ReB2 and Os2B3.

36 MATERIALS SCIENCE↗