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194 records · Page 11
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on Ba16Tb8Nb5(SnO16)3 by Materials Project

Ba16Tb8Nb5(SnO16)3 is (Cubic) Perovskite-derived structured and crystallizes in the tetragonal P4 space group. The structure is three-dimensional. there are eight inequivalent Ba2+ sites. In the first Ba2+ site, Ba2+ is bonded to twelve O2- atoms to form BaO12 cuboctahedra that share corners with twelve BaO12 cuboctahedra, faces with six BaO12 cuboctahedra, faces with two equivalent NbO6 octahedra, faces with two equivalent SnO6 octahedra, and faces with four TbO6 octahedra. There are a spread of Ba–O bond distances ranging from 2.98–3.12 Å. In the second Ba2+ site, Ba2+ is bonded to twelve O2- atoms to form BaO12 cuboctahedra that share corners with twelve BaO12 cuboctahedra, faces with six BaO12 cuboctahedra, faces with four TbO6 octahedra, and faces with four NbO6 octahedra. There are a spread of Ba–O bond distances ranging from 2.98–3.10 Å. In the third Ba2+ site, Ba2+ is bonded to twelve O2- atoms to form BaO12 cuboctahedra that share corners with twelve BaO12 cuboctahedra, faces with six BaO12 cuboctahedra, faces with four TbO6 octahedra, and faces with four NbO6 octahedra. There are a spread of Ba–O bond distances ranging from 2.97–3.12 Å. In the fourth Ba2+ site, Ba2+ is bonded to twelve O2- atoms to form BaO12 cuboctahedra that share corners with twelve BaO12 cuboctahedra, faces with six BaO12 cuboctahedra, faces with two equivalent NbO6 octahedra, faces with two equivalent SnO6 octahedra, and faces with four TbO6 octahedra. There are a spread of Ba–O bond distances ranging from 2.97–3.15 Å. In the fifth Ba2+ site, Ba2+ is bonded to twelve O2- atoms to form BaO12 cuboctahedra that share corners with twelve BaO12 cuboctahedra, faces with six BaO12 cuboctahedra, faces with two equivalent NbO6 octahedra, faces with two equivalent SnO6 octahedra, and faces with four TbO6 octahedra. There are a spread of Ba–O bond distances ranging from 2.97–3.13 Å. In the sixth Ba2+ site, Ba2+ is bonded to twelve O2- atoms to form BaO12 cuboctahedra that share corners with twelve BaO12 cuboctahedra, faces with six BaO12 cuboctahedra, faces with two equivalent NbO6 octahedra, faces with two equivalent SnO6 octahedra, and faces with four TbO6 octahedra. There are a spread of Ba–O bond distances ranging from 2.99–3.11 Å. In the seventh Ba2+ site, Ba2+ is bonded to twelve O2- atoms to form BaO12 cuboctahedra that share corners with twelve BaO12 cuboctahedra, faces with six BaO12 cuboctahedra, faces with two equivalent NbO6 octahedra, faces with two equivalent SnO6 octahedra, and faces with four TbO6 octahedra. There are a spread of Ba–O bond distances ranging from 2.98–3.11 Å. In the eighth Ba2+ site, Ba2+ is bonded to twelve O2- atoms to form BaO12 cuboctahedra that share corners with twelve BaO12 cuboctahedra, faces with six BaO12 cuboctahedra, faces with two equivalent NbO6 octahedra, faces with two equivalent SnO6 octahedra, and faces with four TbO6 octahedra. There are a spread of Ba–O bond distances ranging from 3.00–3.12 Å. There are eight inequivalent Tb+3.38+ sites. In the first Tb+3.38+ site, Tb+3.38+ is bonded to six O2- atoms to form TbO6 octahedra that share a cornercorner with one TbO6 octahedra, corners with five NbO6 octahedra, and faces with eight BaO12 cuboctahedra. The corner-sharing octahedra tilt angles range from 0–4°. There are one shorter (2.17 Å) and five longer (2.28 Å) Tb–O bond lengths. In the second Tb+3.38+ site, Tb+3.38+ is bonded to six O2- atoms to form TbO6 octahedra that share corners with six NbO6 octahedra and faces with eight BaO12 cuboctahedra. The corner-sharing octahedra tilt angles range from 0–4°. There are a spread of Tb–O bond distances ranging from 2.26–2.29 Å. In the third Tb+3.38+ site, Tb+3.38+ is bonded to six O2- atoms to form TbO6 octahedra that share a cornercorner with one SnO6 octahedra, corners with five NbO6 octahedra, and faces with eight BaO12 cuboctahedra. The corner-sharing octahedra tilt angles range from 0–4°. There are a spread of Tb–O bond distances ranging from 2.20–2.29 Å. In the fourth Tb+3.38+ site, Tb+3.38+ is bonded to six O2- atoms to form TbO6 octahedra that share corners with two NbO6 octahedra, corners with four equivalent SnO6 octahedra, and faces with eight BaO12 cuboctahedra. The corner-sharing octahedra tilt angles range from 0–4°. There are a spread of Tb–O bond distances ranging from 2.23–2.30 Å. In the fifth Tb+3.38+ site, Tb+3.38+ is bonded to six O2- atoms to form TbO6 octahedra that share corners with two SnO6 octahedra, corners with four equivalent NbO6 octahedra, and faces with eight BaO12 cuboctahedra. The corner-sharing octahedra tilt angles range from 0–4°. There are a spread of Tb–O bond distances ranging from 2.21–2.28 Å. In the sixth Tb+3.38+ site, Tb+3.38+ is bonded to six O2- atoms to form TbO6 octahedra that share a cornercorner with one TbO6 octahedra, a cornercorner with one NbO6 octahedra, corners with four equivalent SnO6 octahedra, and faces with eight BaO12 cuboctahedra. The corner-sharing octahedra tilt angles range from 0–4°. There are a spread of Tb–O bond distances ranging from 2.18–2.29 Å. In the seventh Tb+3.38+ site, Tb+3.38+ is bonded to six O2- atoms to form TbO6 octahedra that share a cornercorner with one TbO6 octahedra, a cornercorner with one SnO6 octahedra, corners with four equivalent NbO6 octahedra, and faces with eight BaO12 cuboctahedra. The corner-sharing octahedra tilt angles range from 0–4°. There are a spread of Tb–O bond distances ranging from 2.20–2.28 Å. In the eighth Tb+3.38+ site, Tb+3.38+ is bonded to six O2- atoms to form TbO6 octahedra that share a cornercorner with one TbO6 octahedra, a cornercorner with one NbO6 octahedra, corners with four equivalent SnO6 octahedra, and faces with eight BaO12 cuboctahedra. The corner-sharing octahedra tilt angles range from 0–4°. There are a spread of Tb–O bond distances ranging from 2.19–2.33 Å. There are five inequivalent Nb5+ sites. In the first Nb5+ site, Nb5+ is bonded to six O2- atoms to form NbO6 octahedra that share a cornercorner with one SnO6 octahedra, corners with five TbO6 octahedra, and faces with eight BaO12 cuboctahedra. The corner-sharing octahedra tilt angles range from 0–4°. There are a spread of Nb–O bond distances ranging from 2.02–2.07 Å. In the second Nb5+ site, Nb5+ is bonded to six O2- atoms to form NbO6 octahedra that share corners with six TbO6 octahedra and faces with eight BaO12 cuboctahedra. The corner-sharing octahedra tilt angles range from 0–4°. All Nb–O bond lengths are 2.03 Å. In the third Nb5+ site, Nb5+ is bonded to six O2- atoms to form NbO6 octahedra that share corners with six TbO6 octahedra and faces with eight BaO12 cuboctahedra. The corner-sharing octahedra tilt angles range from 0–4°. There are a spread of Nb–O bond distances ranging from 2.01–2.06 Å. In the fourth Nb5+ site, Nb5+ is bonded to six O2- atoms to form NbO6 octahedra that share corners with six TbO6 octahedra and faces with eight BaO12 cuboctahedra. The corner-sharing octahedra tilt angles range from 0–4°. There are one shorter (2.02 Å) and five longer (2.03 Å) Nb–O bond lengths. In the fifth Nb5+ site, Nb5+ is bonded to six O2- atoms to form NbO6 octahedra that share a cornercorner with one SnO6 octahedra, corners with five TbO6 octahedra, and faces with eight BaO12 cuboctahedra. The corner-sharing octahedra tilt angles range from 0–4°. There are a spread of Nb–O bond distances ranging from 2.00–2.07 Å. There are three inequivalent Sn4+ sites. In the first Sn4+ site, Sn4+ is bonded to six O2- atoms to form SnO6 octahedra that share corners with six TbO6 octahedra and faces with eight BaO12 cuboctahedra. The corner-sharing octahedra tilt angles range from 0–4°. There are a spread of Sn–O bond distances ranging from 2.08–2.10 Å. In the second Sn4+ site, Sn4+ is bonded to six O2- atoms to form SnO6 octahedra that share a cornercorner with one NbO6 octahedra, corners with five TbO6 octahedra, and faces with eight BaO12 cuboctahedra. The corner-sharing octahedra tilt angles range from 0–4°. There are a spread of Sn–O bond distances ranging from 2.06–2.22 Å. In the third Sn4+ site, Sn4+ is bonded to six O2- atoms to form SnO6 octahedra that share a cornercorner with one NbO6 octahedra, corners with five TbO6 octahedra, and faces with eight BaO12 cuboctahedra. The corner-sharing octahedra tilt angles range from 0–4°. There are a spread of Sn–O bond distances ranging from 2.07–2.22 Å. There are twenty-four inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted linear geometry to four equivalent Ba2+ and two Tb+3.38+ atoms. In the second O2- site, O2- is bonded in a distorted linear geometry to four Ba2+, one Tb+3.38+, and one Nb5+ atom. In the third O2- site, O2- is bonded in a distorted linear geometry to four equivalent Ba2+, one Tb+3.38+, and one Nb5+ atom. In the fourth O2- site, O2- is bonded in a distorted linear geometry to four equivalent Ba2+, one Nb5+, and one Sn4+ atom. In the fifth O2- site, O2- is bonded in a distorted linear geometry to four Ba2+, one Tb+3.38+, and one Nb5+ atom. In the sixth O2- site, O2- is bonded in a distorted linear geometry to four equivalent Ba2+, one Tb+3.38+, and one Nb5+ atom. In the seventh O2- site, O2- is bonded in a distorted linear geometry to four equivalent Ba2+, one Tb+3.38+, and one Nb5+ atom. In the eighth O2- site, O2- is bonded in a distorted linear geometry to four Ba2+, one Tb+3.38+, and one Nb5+ atom. In the ninth O2- site, O2- is bonded in a distorted linear geometry to four equivalent Ba2+, one Tb+3.38+, and one Nb5+ atom. In the tenth O2- site, O2- is bonded in a distorted linear geometry to four equivalent Ba2+, one Tb+3.38+, and one Nb5+ atom. In the eleventh O2- site, O2- is bonded in a distorted linear geometry to four Ba2+, one Tb+3.38+, and one Sn4+ atom. In the twelfth O2- site, O2- is bonded in a distorted linear geometry to four equivalent Ba2+, one Tb+3.38+, and one Sn4+ atom. In the thirteenth O2- site, O2- is bonded in a distorted linear geometry to four equivalent Ba2+, one Tb+3.38+, and one Sn4+ atom. In the fourteenth O2- site, O2- is bonded in a distorted linear geometry to four Ba2+, one Tb+3.38+, and one Nb5+ atom. In the fifteenth O2- site, O2- is bonded in a distorted linear geometry to four equivalent Ba2+, one Tb+3.38+, and one Nb5+ atom. In the sixteenth O2- site, O2- is bonded in a distorted linear geometry to four equivalent Ba2+, one Tb+3.38+, and one Nb5+ atom. In the seventeenth O2- site, O2- is bonded in a distorted linear geometry to four Ba2+, one Tb+3.38+, and one Sn4+ atom. In the eighteenth O2- site, O2- is bonded in a distorted linear geometry to four equivalent Ba2+, one Nb5+, and one Sn4+ atom. In the nineteenth O2- site, O2- is bonded in a distorted linear geometry to four equivalent Ba2+, one Tb+3.38+, and one Sn4+ atom. In the twentieth O2- site, O2- is bonded in a distorted linear geometry to four Ba2+, one Tb+3.38+, and one Nb5+ atom. In the twenty-first O2- site, O2- is bonded in a distorted linear geometry to four equivalent Ba2+, one Tb+3.38+, and one Sn4+ atom. In the twenty-second O2- site, O2- is bonded in a distorted linear geometry to four equivalent Ba2+ and two Tb+3.38+ atoms. In the twenty-third O2- site, O2- is bonded in a distorted linear geometry to four Ba2+, one Tb+3.38+, and one Sn4+ atom. In the twenty-fourth O2- site, O2- is bonded in a distorted linear geometry to four equivalent Ba2+, one Tb+3.38+, and one Nb5+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Stability Frontiers in the AM 6 X 6 Kagome Metals: The Ln Nb 6 Sn 6 ( Ln :Ce–Lu,Y) Family and Density-Wave Transition in LuNb 6 Sn 6

The kagome motif is a versatile platform for condensed matter physics, hosting rich interactions between magnetic, electronic, and structural degrees of freedom. In recent years, the discovery of a charge density wave (CDW) in the AV 3 Sb 5 superconductors and structurally-derived bond density waves (BDW) in FeGe and ScV 6 Sn 6 have stoked the search for new kagome platforms broadly exhibiting density wave (DW) transitions. Here, in this work, we evaluate the known AM 6 X 6 chemistries and construct a stability diagram that summarizes the structural relationships among the >125 member family. Subsequently, we introduce our discovery of the broader LnNb 6 Sn 6 (Ln:Ce–Nd,Sm,Gd–Tm,Lu,Y) family of kagome metals and an analogous DW transition in LuNb 6 Sn 6 . Our X-ray scattering measurements clearly indicate a (1/3, 1/3, 1/3) ordering wave vector (√$\bar{3}$ x √$\bar{3}$ x $3$ superlattice) and diffuse scattering on half-integer L-planes. Our analysis of the structural data supports the “rattling mode” DW model proposed for ScV 6 Sn 6 and paints a detailed picture of the steric interactions between the rare-earth filler element and the host Nb–Sn kagome scaffolding. We also provide a broad survey of the magnetic properties within the HfFe 6 Ge 6 -type LnNb 6 Sn 6 members, revealing a number of complex antiferromagnetic and metamagnetic transitions throughout the family. This work integrates our new LnNb 6 Sn 6 series of compounds into the broader AM 6 X 6 family, providing new material platforms and forging a new route forward at the frontier of kagome metal research.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Materials Data on Nb2SnO6 by Materials Project

SnNb2O6 crystallizes in the monoclinic C2/c space group. The structure is three-dimensional. Nb5+ is bonded to six O2- atoms to form a mixture of distorted edge and corner-sharing NbO6 octahedra. The corner-sharing octahedra tilt angles range from 29–56°. There are a spread of Nb–O bond distances ranging from 1.86–2.25 Å. Sn2+ is bonded in a distorted rectangular see-saw-like geometry to four equivalent O2- atoms. There are two shorter (2.20 Å) and two longer (2.40 Å) Sn–O bond lengths. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted trigonal planar geometry to three equivalent Nb5+ atoms. In the second O2- site, O2- is bonded in a bent 150 degrees geometry to two equivalent Nb5+ atoms. In the third O2- site, O2- is bonded in a 3-coordinate geometry to one Nb5+ and two equivalent Sn2+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Co‐Doping Approach for Enhanced Electron Extraction to TiO 2 for Stable Inorganic Perovskite Solar Cells

Inorganic perovskite CsPbI 3 solar cells hold great potential for improving the operational stability of perovskite photovoltaics. However, electron extraction is limited by the low conductivity of TiO 2 , representing a bottleneck for achieving stable performance. In this study, a co‐doping strategy for TiO 2 using Nb(V) and Sn(IV), which reduces the material's work function by 80 meV compared to Nb(V) mono‐doped TiO 2 , is introduced. To gain fundamental understanding of the processes at the interfaces between the perovskite and charge‐selective layer, transient surface photovoltage measurements are applied, revealing the beneficial effect of the energetic and structural modification on electron extraction across the CsPbI 3 /TiO 2 interface. Using 2D drift‐diffusion simulations, it is found that co‐doping reduces the interface hole recombination velocity by two orders of magnitude, increasing the concentration of extracted electrons by 20%. When integrated into n–i–p solar cells, co‐doped TiO 2 enhances the projected T S80 lifetimes under continuous AM1.5G illumination by a factor of 25 compared to mono‐doped TiO 2 . This study provides fundamental insights into interfacial charge extraction and its correlation with operational stability of perovskite solar cells, offering potential applications for other charge‐selective contacts.

14 SOLAR ENERGY↗
DOE OSTI2022

Fabrication of Nb3Sn by Magnetron Sputtering for Superconducting Radiofrequency Application

Particle accelerators are considered as an important device that has wide applications in cancer treatment, sterilizing waste, preserving foods, ion implantation in semiconductor industry, and in production of isotopes for medical applications. Superconducting radiofrequency (SRF) cavities are the building blocks of a linear particle accelerator. Current particle accelerators use niobium (Nb) superconductors as the sheet material to fabricate a single SRF cavity for particle acceleration. With better superconducting properties (critical temperature Tc ~ 18.3 K, superheating field Hsh~ 400 mT), Nb3Sn is considered a potential candidate in SRF technology. Magnetron sputtering is a promising deposition method to fabricate Nb3Sn thin films inside SRF cavities. Superconducting Nb3Sn films were fabricated on Nb and sapphire substrates by magnetron sputtering from a single stoichiometric Nb3Sn target, by multilayer sputtering of Nb and Sn followed by annealing, and by co-sputtering of Nb and Sn followed by annealing. The variation of morphological and superconducting properties was investigated for different substrate temperatures, annealing temperatures, annealing durations, and thicknesses. The film properties were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), and energy dispersive X-ray spectroscopy (EDS). The films had crystalline Nb3Sn structure without any presence of poor superconducting Nb6Sn5 and NbSn2 phases. The highest Tc of the films fabricated from the stoichiometric target, multilayer sputtering and co-sputtering were 17.44, 17.93, and 17.66 K respectively. Finally, a cylindrical sputter coater with two identical magnetrons was designed and commissioned to fabricate Nb3Sn films inside a 2.6 GHz SRF cavity. The magnetrons were installed facing opposite to each other in a custom designed vacuum chamber and multilayers of Nb and Sn films on 1 cm2 Nb substrates replicating the beam tubes and equator locations of the cavity and the coated multilayered films were annealed at 950 °C for 3 h. The XRD of the as?deposited and annealed films confirmed the formation of Nb3Sn after the annealing. The dissertation discusses the fabrication process, characterized results of the fabricated films, the design of the cylindrical sputter coater and the preliminary data obtained from the sputter coater.

Sayeed, Md Nizam↗
DOE OSTI2020

Determining Multi-Component Phase Diagrams with Desired Characteristics Using Active Learning

Herein, we demonstrate how to predict and experimentally validate phase diagrams for multi-component systems from a high-dimensional virtual space of all possible phase diagrams involving several elements based on small existing experimental data. The experimental data for bulk phases for known systems represents a sampling from this space, and screening the space allows multi-component phase diagrams with given design criteria to be built. This approach uses machine learning methods to predict phase diagrams and Bayesian experimental design to minimize experiments for refinement and validation, all within an active learning loop. The approach is proven by predicting and synthesizing the ferroelectric ceramic system (1-ω)(Ba 0.61 Ca 0.28 Sr 0.11 TiO 3 )-ω(BaTi 0.888 Zr 0.0616 Sn 0.0028 Hf 0.0476 O 3 ) with a relatively high transition temperature and triple point, as well as the NiTi-based pseudo-binary phase diagram (1-ω)(Ti 0.309 Ni 0.485 Hf 0.20 Zr 0.006 )-ω(Ti 0.309 Ni 0.485 Hf 0.07 Zr 0.068 Nb 0.068 ) designed for high transition temperature (ω ≤ 1). Each phase diagram is validated and optimized through only three new experiments. The complexity of these compounds is beyond the reach of today’s computational methods.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Unveiling the nucleation and growth of Zr oxide precipitates in internally oxidized Nb3Sn superconductors

We report on atomic-scale analyses of nucleation and growth of Zr oxide precipitates and the microstructural evolution of internally oxidized Nb3Sn wires for high-field superconducting magnet applications, utilizing atom probe tomography (APT), transmission electron microscopy (TEM), and first-principles calculations. APT analyses reveal that oxygen and zirconium are already segregated at grain boundaries (GBs) in the unreacted Nb-1Zr-4Ta (at%) alloy prior to forming Nb3Sn through reacting the Nb alloy with Sn and SnO2. After forming Nb3Sn, Zr oxide precipitates nucleate both at the Nb3Sn/Nb heterophase interfaces and in the Nb3Sn grains, driven by the small solubilities of Zr and O in Nb3Sn compared to their value in Nb. A high number density (Nv) of Zr oxide nanoprecipitates is observed in the Nb3Sn layers, ∼10 23 m −3 , with a mean diameter <10 nm for a heat treatment at 625 °C. Quantitative APT and TEM analyses of the Zr oxide precipitates in the reacted Nb3Sn layers elucidate details of the nucleation, growth, and coarsening processes of the Zr oxide precipitates in Nb3Sn. First-principles calculations and classical nucleation theory are employed to study the nucleation of Zr oxide precipitates in Nb3Sn and to estimate the maximum energy barrier and critical radius for nucleation. Our research unveils the kinetic pathways for nucleation and growth of Zr oxide precipitates and the microstructural evolution of Nb3Sn layers, which helps to understand and improve the superconducting properties of internally oxidized Nb3Sn wires for use in high-field superconducting magnets. •We investigated the nucleation and growth of Zr oxide nanoprecipitates in Nb3Sn superconductors for magnet applications.•APT and TEM analyses reveals the nucleation and growth process of Zr oxide precipitates in Nb3Sn layers.•Classical nucleation theory with DFT is employed to describe the nucleation process of Zr oxide precipitates in Nb3Sn.•We find that the interfacial reactions at Nb/Nb3Sn interface play a critical role in the nucleation of Zr oxide precipitates.•Current study provides a pathway to improve the properties of internally oxidized Nb3Sn superconducting wires.

43 PARTICLE ACCELERATORS↗
DOE OSTI2020

Materials Data on Mg30NbSnO32 by Materials Project

Mg30NbSnO32 is alpha Po-derived structured and crystallizes in the tetragonal P4/mmm space group. The structure is three-dimensional. there are eight inequivalent Mg2+ sites. In the first Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with two equivalent MgO6 octahedra, corners with two equivalent NbO6 octahedra, corners with two equivalent SnO6 octahedra, and edges with twelve MgO6 octahedra. The corner-sharing octahedral tilt angles are 0°. There are a spread of Mg–O bond distances ranging from 2.00–2.19 Å. In the second Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with two equivalent SnO6 octahedra, corners with four equivalent MgO6 octahedra, and edges with twelve MgO6 octahedra. The corner-sharing octahedral tilt angles are 0°. There are two shorter (1.98 Å) and four longer (2.18 Å) Mg–O bond lengths. In the third Mg2+ site, Mg2+ is bonded to six O2- atoms to form a mixture of edge and corner-sharing MgO6 octahedra. The corner-sharing octahedral tilt angles are 0°. There are a spread of Mg–O bond distances ranging from 2.12–2.15 Å. In the fourth Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with two equivalent NbO6 octahedra, corners with four equivalent MgO6 octahedra, and edges with twelve MgO6 octahedra. The corner-sharing octahedral tilt angles are 0°. There are two shorter (2.05 Å) and four longer (2.16 Å) Mg–O bond lengths. In the fifth Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with six MgO6 octahedra, an edgeedge with one NbO6 octahedra, an edgeedge with one SnO6 octahedra, and edges with ten MgO6 octahedra. The corner-sharing octahedra tilt angles range from 1–8°. There are a spread of Mg–O bond distances ranging from 2.14–2.18 Å. In the sixth Mg2+ site, Mg2+ is bonded to six O2- atoms to form a mixture of edge and corner-sharing MgO6 octahedra. The corner-sharing octahedra tilt angles range from 0–1°. All Mg–O bond lengths are 2.16 Å. In the seventh Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with six MgO6 octahedra, an edgeedge with one SnO6 octahedra, and edges with eleven MgO6 octahedra. The corner-sharing octahedra tilt angles range from 0–7°. There are a spread of Mg–O bond distances ranging from 2.12–2.20 Å. In the eighth Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with six MgO6 octahedra, an edgeedge with one NbO6 octahedra, and edges with eleven MgO6 octahedra. The corner-sharing octahedra tilt angles range from 0–5°. There are a spread of Mg–O bond distances ranging from 2.14–2.17 Å. Nb2+ is bonded to six O2- atoms to form NbO6 octahedra that share corners with six MgO6 octahedra and edges with twelve MgO6 octahedra. The corner-sharing octahedral tilt angles are 0°. There are four shorter (2.24 Å) and two longer (2.26 Å) Nb–O bond lengths. Sn2+ is bonded to six O2- atoms to form SnO6 octahedra that share corners with six MgO6 octahedra and edges with twelve MgO6 octahedra. The corner-sharing octahedral tilt angles are 0°. There are four shorter (2.32 Å) and two longer (2.33 Å) Sn–O bond lengths. There are twelve inequivalent O2- sites. In the first O2- site, O2- is bonded to five Mg2+ and one Sn2+ atom to form OMg5Sn octahedra that share corners with six OMg5Sn octahedra and edges with twelve OMg6 octahedra. The corner-sharing octahedra tilt angles range from 0–4°. In the second O2- site, O2- is bonded to six Mg2+ atoms to form OMg6 octahedra that share corners with six OMg5Sn octahedra and edges with twelve OMg6 octahedra. The corner-sharing octahedra tilt angles range from 0–4°. In the third O2- site, O2- is bonded to five Mg2+ and one Nb2+ atom to form a mixture of edge and corner-sharing OMg5Nb octahedra. The corner-sharing octahedra tilt angles range from 0–3°. In the fourth O2- site, O2- is bonded to six Mg2+ atoms to form OMg6 octahedra that share corners with six equivalent OMg6 octahedra and edges with twelve OMg5Sn octahedra. The corner-sharing octahedra tilt angles range from 0–3°. In the fifth O2- site, O2- is bonded to five Mg2+ and one Sn2+ atom to form a mixture of edge and corner-sharing OMg5Sn octahedra. The corner-sharing octahedra tilt angles range from 0–3°. In the sixth O2- site, O2- is bonded to five Mg2+ and one Sn2+ atom to form a mixture of edge and corner-sharing OMg5Sn octahedra. The corner-sharing octahedra tilt angles range from 0–3°. There are two shorter (2.18 Å) and two longer (2.19 Å) O–Mg bond lengths. In the seventh O2- site, O2- is bonded to five Mg2+ and one Nb2+ atom to form OMg5Nb octahedra that share corners with six OMg5Sn octahedra and edges with twelve OMg6 octahedra. The corner-sharing octahedra tilt angles range from 0–2°. The O–Mg bond length is 2.07 Å. In the eighth O2- site, O2- is bonded to five Mg2+ and one Nb2+ atom to form OMg5Nb octahedra that share corners with six OMg5Sn octahedra and edges with twelve OMg6 octahedra. The corner-sharing octahedra tilt angles range from 0–2°. There are a spread of O–Mg bond distances ranging from 2.07–2.17 Å. In the ninth O2- site, O2- is bonded to six Mg2+ atoms to form a mixture of edge and corner-sharing OMg6 octahedra. The corner-sharing octahedra tilt angles range from 0–3°. In the tenth O2- site, O2- is bonded to six Mg2+ atoms to form OMg6 octahedra that share corners with six OMg5Nb octahedra and edges with twelve OMg6 octahedra. The corner-sharing octahedra tilt angles range from 0–2°. In the eleventh O2- site, O2- is bonded to five Mg2+ and one Nb2+ atom to form OMg5Nb octahedra that share corners with six OMg5Sn octahedra and edges with twelve OMg6 octahedra. The corner-sharing octahedra tilt angles range from 0–2°. Both O–Mg bond lengths are 2.17 Å. In the twelfth O2- site, O2- is bonded to five Mg2+ and one Nb2+ atom to form OMg5Nb octahedra that share corners with six OMg5Sn octahedra and edges with twelve OMg6 octahedra. The corner-sharing octahedra tilt angles range from 0–2°. There are two shorter (2.14 Å) and two longer (2.17 Å) O–Mg bond lengths.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on LiNbSn3(PO4)6 by Materials Project

LiNbSn3(PO4)6 crystallizes in the trigonal R3 space group. The structure is three-dimensional. Li1+ is bonded in a distorted hexagonal planar geometry to six O2- atoms. There are three shorter (2.32 Å) and three longer (2.64 Å) Li–O bond lengths. Nb5+ is bonded to six O2- atoms to form NbO6 octahedra that share corners with six PO4 tetrahedra. There are three shorter (1.99 Å) and three longer (2.01 Å) Nb–O bond lengths. There are three inequivalent Sn4+ sites. In the first Sn4+ site, Sn4+ is bonded to six O2- atoms to form SnO6 octahedra that share corners with six PO4 tetrahedra. There are three shorter (2.02 Å) and three longer (2.07 Å) Sn–O bond lengths. In the second Sn4+ site, Sn4+ is bonded to six O2- atoms to form SnO6 octahedra that share corners with six PO4 tetrahedra. There are three shorter (2.05 Å) and three longer (2.06 Å) Sn–O bond lengths. In the third Sn4+ site, Sn4+ is bonded to six O2- atoms to form SnO6 octahedra that share corners with six PO4 tetrahedra. There are three shorter (2.02 Å) and three longer (2.04 Å) Sn–O bond lengths. There are two inequivalent P5+ sites. In the first P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share a cornercorner with one NbO6 octahedra and corners with three SnO6 octahedra. The corner-sharing octahedra tilt angles range from 20–39°. There are a spread of P–O bond distances ranging from 1.53–1.57 Å. In the second P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share a cornercorner with one NbO6 octahedra and corners with three SnO6 octahedra. The corner-sharing octahedra tilt angles range from 28–34°. There are a spread of P–O bond distances ranging from 1.52–1.58 Å. There are eight inequivalent O2- sites. In the first O2- site, O2- is bonded in a bent 150 degrees geometry to one Sn4+ and one P5+ atom. In the second O2- site, O2- is bonded in a 3-coordinate geometry to one Li1+, one Sn4+, and one P5+ atom. In the third O2- site, O2- is bonded in a bent 150 degrees geometry to one Sn4+ and one P5+ atom. In the fourth O2- site, O2- is bonded in a bent 150 degrees geometry to one Nb5+ and one P5+ atom. In the fifth O2- site, O2- is bonded in a bent 150 degrees geometry to one Sn4+ and one P5+ atom. In the sixth O2- site, O2- is bonded in a 2-coordinate geometry to one Li1+, one Nb5+, and one P5+ atom. In the seventh O2- site, O2- is bonded in a bent 150 degrees geometry to one Sn4+ and one P5+ atom. In the eighth O2- site, O2- is bonded in a bent 150 degrees geometry to one Sn4+ and one P5+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on K8NbSnAs5 by Materials Project

K8NbSnAs5 crystallizes in the monoclinic C2/c space group. The structure is three-dimensional. there are eight inequivalent K1+ sites. In the first K1+ site, K1+ is bonded in a 4-coordinate geometry to four As3- atoms. There are a spread of K–As bond distances ranging from 3.33–3.74 Å. In the second K1+ site, K1+ is bonded in a 3-coordinate geometry to one K1+ and five As3- atoms. The K–K bond length is 3.57 Å. There are a spread of K–As bond distances ranging from 3.38–3.95 Å. In the third K1+ site, K1+ is bonded in a 4-coordinate geometry to four As3- atoms. There are a spread of K–As bond distances ranging from 3.32–3.69 Å. In the fourth K1+ site, K1+ is bonded in a 5-coordinate geometry to five As3- atoms. There are a spread of K–As bond distances ranging from 3.47–3.82 Å. In the fifth K1+ site, K1+ is bonded to four As3- atoms to form distorted KAs4 tetrahedra that share an edgeedge with one KAs4 tetrahedra and an edgeedge with one NbAs4 tetrahedra. There are a spread of K–As bond distances ranging from 3.37–3.43 Å. In the sixth K1+ site, K1+ is bonded in a 4-coordinate geometry to four As3- atoms. There are a spread of K–As bond distances ranging from 3.36–3.66 Å. In the seventh K1+ site, K1+ is bonded in a 3-coordinate geometry to three As3- atoms. There are a spread of K–As bond distances ranging from 3.36–3.56 Å. In the eighth K1+ site, K1+ is bonded in a 5-coordinate geometry to one K1+ and five As3- atoms. There are a spread of K–As bond distances ranging from 3.27–3.64 Å. Nb5+ is bonded to four As3- atoms to form NbAs4 tetrahedra that share an edgeedge with one KAs4 tetrahedra. There are a spread of Nb–As bond distances ranging from 2.49–2.58 Å. Sn2+ is bonded in a trigonal non-coplanar geometry to three As3- atoms. There are a spread of Sn–As bond distances ranging from 2.67–2.79 Å. There are five inequivalent As3- sites. In the first As3- site, As3- is bonded in a 1-coordinate geometry to five K1+, one Nb5+, and one Sn2+ atom. In the second As3- site, As3- is bonded in a 1-coordinate geometry to eight K1+ and one Nb5+ atom. In the third As3- site, As3- is bonded in a 8-coordinate geometry to seven K1+ and one Sn2+ atom. In the fourth As3- site, As3- is bonded in a 1-coordinate geometry to seven K1+, one Nb5+, and one Sn2+ atom. In the fifth As3- site, As3- is bonded in a 1-coordinate geometry to seven K1+ and one Nb5+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Mg30NbSnO32 by Materials Project

Mg30NbSnO32 is alpha Po-derived structured and crystallizes in the tetragonal P4/mmm space group. The structure is three-dimensional. there are eight inequivalent Mg2+ sites. In the first Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with two equivalent SnO6 octahedra, corners with four MgO6 octahedra, and edges with twelve MgO6 octahedra. The corner-sharing octahedral tilt angles are 0°. There are a spread of Mg–O bond distances ranging from 1.97–2.19 Å. In the second Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with two equivalent NbO6 octahedra, corners with four MgO6 octahedra, and edges with twelve MgO6 octahedra. The corner-sharing octahedral tilt angles are 0°. There are a spread of Mg–O bond distances ranging from 2.04–2.17 Å. In the third Mg2+ site, Mg2+ is bonded to six O2- atoms to form a mixture of edge and corner-sharing MgO6 octahedra. The corner-sharing octahedral tilt angles are 0°. There are four shorter (2.13 Å) and two longer (2.17 Å) Mg–O bond lengths. In the fourth Mg2+ site, Mg2+ is bonded to six O2- atoms to form a mixture of edge and corner-sharing MgO6 octahedra. The corner-sharing octahedral tilt angles are 0°. There are four shorter (2.14 Å) and two longer (2.17 Å) Mg–O bond lengths. In the fifth Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with six MgO6 octahedra, an edgeedge with one NbO6 octahedra, an edgeedge with one SnO6 octahedra, and edges with ten MgO6 octahedra. The corner-sharing octahedra tilt angles range from 0–7°. There are a spread of Mg–O bond distances ranging from 2.10–2.21 Å. In the sixth Mg2+ site, Mg2+ is bonded to six O2- atoms to form a mixture of edge and corner-sharing MgO6 octahedra. The corner-sharing octahedra tilt angles range from 0–2°. There are a spread of Mg–O bond distances ranging from 2.15–2.17 Å. In the seventh Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with six MgO6 octahedra, an edgeedge with one SnO6 octahedra, and edges with eleven MgO6 octahedra. The corner-sharing octahedra tilt angles range from 0–8°. There are a spread of Mg–O bond distances ranging from 2.12–2.19 Å. In the eighth Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with six MgO6 octahedra, an edgeedge with one NbO6 octahedra, and edges with eleven MgO6 octahedra. The corner-sharing octahedra tilt angles range from 0–5°. There are two shorter (2.14 Å) and four longer (2.17 Å) Mg–O bond lengths. Nb2+ is bonded to six O2- atoms to form NbO6 octahedra that share corners with two equivalent SnO6 octahedra, corners with four equivalent MgO6 octahedra, and edges with twelve MgO6 octahedra. The corner-sharing octahedral tilt angles are 0°. There are two shorter (2.13 Å) and four longer (2.26 Å) Nb–O bond lengths. Sn2+ is bonded to six O2- atoms to form SnO6 octahedra that share corners with two equivalent NbO6 octahedra, corners with four equivalent MgO6 octahedra, and edges with twelve MgO6 octahedra. The corner-sharing octahedral tilt angles are 0°. There are two shorter (2.21 Å) and four longer (2.34 Å) Sn–O bond lengths. There are eleven inequivalent O2- sites. In the first O2- site, O2- is bonded to five Mg2+ and one Sn2+ atom to form OMg5Sn octahedra that share corners with six OMg5Nb octahedra and edges with twelve OMg5Sn octahedra. The corner-sharing octahedra tilt angles range from 0–5°. In the second O2- site, O2- is bonded to five Mg2+ and one Nb2+ atom to form OMg5Nb octahedra that share corners with six OMg5Sn octahedra and edges with twelve OMg5Nb octahedra. The corner-sharing octahedra tilt angles range from 0–5°. In the third O2- site, O2- is bonded to six Mg2+ atoms to form a mixture of edge and corner-sharing OMg6 octahedra. The corner-sharing octahedra tilt angles range from 0–4°. Both O–Mg bond lengths are 2.17 Å. In the fourth O2- site, O2- is bonded to six Mg2+ atoms to form a mixture of edge and corner-sharing OMg6 octahedra. The corner-sharing octahedra tilt angles range from 0–2°. In the fifth O2- site, O2- is bonded to five Mg2+ and one Sn2+ atom to form a mixture of edge and corner-sharing OMg5Sn octahedra. The corner-sharing octahedra tilt angles range from 0–5°. There are one shorter (1.97 Å) and four longer (2.19 Å) O–Mg bond lengths. In the sixth O2- site, O2- is bonded to five Mg2+ and one Nb2+ atom to form a mixture of edge and corner-sharing OMg5Nb octahedra. The corner-sharing octahedra tilt angles range from 0–5°. There are two shorter (2.16 Å) and two longer (2.17 Å) O–Mg bond lengths. In the seventh O2- site, O2- is bonded to six Mg2+ atoms to form OMg6 octahedra that share corners with six OMg6 octahedra and edges with twelve OMg5Sn octahedra. The corner-sharing octahedra tilt angles range from 0–4°. In the eighth O2- site, O2- is bonded to six Mg2+ atoms to form OMg6 octahedra that share corners with six equivalent OMg6 octahedra and edges with twelve OMg5Sn octahedra. The corner-sharing octahedra tilt angles range from 0–3°. In the ninth O2- site, O2- is bonded to four equivalent Mg2+, one Nb2+, and one Sn2+ atom to form OMg4NbSn octahedra that share corners with six OMg4NbSn octahedra and edges with twelve OMg5Sn octahedra. The corner-sharing octahedra tilt angles range from 0–1°. In the tenth O2- site, O2- is bonded to six Mg2+ atoms to form OMg6 octahedra that share corners with six OMg4NbSn octahedra and edges with twelve OMg5Sn octahedra. The corner-sharing octahedra tilt angles range from 0–1°. In the eleventh O2- site, O2- is bonded to six Mg2+ atoms to form a mixture of edge and corner-sharing OMg6 octahedra. The corner-sharing octahedra tilt angles range from 0–1°.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on LiNbSn3(PO4)6 by Materials Project

LiNbSn3(PO4)6 crystallizes in the triclinic P1 space group. The structure is three-dimensional. Li1+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Li–O bond distances ranging from 2.06–2.78 Å. Nb5+ is bonded to six O2- atoms to form NbO6 octahedra that share corners with six PO4 tetrahedra. There are a spread of Nb–O bond distances ranging from 1.96–2.04 Å. There are three inequivalent Sn4+ sites. In the first Sn4+ site, Sn4+ is bonded to six O2- atoms to form SnO6 octahedra that share corners with six PO4 tetrahedra. There are a spread of Sn–O bond distances ranging from 2.02–2.05 Å. In the second Sn4+ site, Sn4+ is bonded to six O2- atoms to form SnO6 octahedra that share corners with six PO4 tetrahedra. There are a spread of Sn–O bond distances ranging from 2.04–2.08 Å. In the third Sn4+ site, Sn4+ is bonded to six O2- atoms to form SnO6 octahedra that share corners with six PO4 tetrahedra. There are a spread of Sn–O bond distances ranging from 2.01–2.11 Å. There are six inequivalent P5+ sites. In the first P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share a cornercorner with one NbO6 octahedra and corners with three SnO6 octahedra. The corner-sharing octahedra tilt angles range from 17–38°. There are a spread of P–O bond distances ranging from 1.53–1.58 Å. In the second P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share a cornercorner with one NbO6 octahedra and corners with three SnO6 octahedra. The corner-sharing octahedra tilt angles range from 14–41°. There are a spread of P–O bond distances ranging from 1.53–1.57 Å. In the third P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share a cornercorner with one NbO6 octahedra and corners with three SnO6 octahedra. The corner-sharing octahedra tilt angles range from 21–42°. There are a spread of P–O bond distances ranging from 1.53–1.58 Å. In the fourth P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share a cornercorner with one NbO6 octahedra and corners with three SnO6 octahedra. The corner-sharing octahedra tilt angles range from 24–41°. There are a spread of P–O bond distances ranging from 1.53–1.57 Å. In the fifth P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share a cornercorner with one NbO6 octahedra and corners with three SnO6 octahedra. The corner-sharing octahedra tilt angles range from 18–37°. There are a spread of P–O bond distances ranging from 1.52–1.58 Å. In the sixth P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share a cornercorner with one NbO6 octahedra and corners with three SnO6 octahedra. The corner-sharing octahedra tilt angles range from 23–37°. There are a spread of P–O bond distances ranging from 1.52–1.56 Å. There are twenty-four inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Sn4+ and one P5+ atom. In the second O2- site, O2- is bonded in a bent 150 degrees geometry to one Sn4+ and one P5+ atom. In the third O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Sn4+ and one P5+ atom. In the fourth O2- site, O2- is bonded in a bent 150 degrees geometry to one Sn4+ and one P5+ atom. In the fifth O2- site, O2- is bonded in a bent 150 degrees geometry to one Sn4+ and one P5+ atom. In the sixth O2- site, O2- is bonded in a bent 150 degrees geometry to one Sn4+ and one P5+ atom. In the seventh O2- site, O2- is bonded in a bent 150 degrees geometry to one Sn4+ and one P5+ atom. In the eighth O2- site, O2- is bonded in a bent 150 degrees geometry to one Sn4+ and one P5+ atom. In the ninth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Li1+, one Nb5+, and one P5+ atom. In the tenth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Sn4+ and one P5+ atom. In the eleventh O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Sn4+ and one P5+ atom. In the twelfth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Sn4+ and one P5+ atom. In the thirteenth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Sn4+ and one P5+ atom. In the fourteenth O2- site, O2- is bonded in a distorted T-shaped geometry to one Li1+, one Sn4+, and one P5+ atom. In the fifteenth O2- site, O2- is bonded in a bent 150 degrees geometry to one Sn4+ and one P5+ atom. In the sixteenth O2- site, O2- is bonded in a distorted T-shaped geometry to one Li1+, one Nb5+, and one P5+ atom. In the seventeenth O2- site, O2- is bonded in a 3-coordinate geometry to one Li1+, one Sn4+, and one P5+ atom. In the eighteenth O2- site, O2- is bonded in a bent 150 degrees geometry to one Sn4+ and one P5+ atom. In the nineteenth O2- site, O2- is bonded in a bent 150 degrees geometry to one Nb5+ and one P5+ atom. In the twentieth O2- site, O2- is bonded in a bent 150 degrees geometry to one Sn4+ and one P5+ atom. In the twenty-first O2- site, O2- is bonded in a linear geometry to one Nb5+ and one P5+ atom. In the twenty-second O2- site, O2- is bonded in a 2-coordinate geometry to one Li1+, one Sn4+, and one P5+ atom. In the twenty-third O2- site, O2- is bonded in a 2-coordinate geometry to one Li1+, one Nb5+, and one P5+ atom. In the twenty-fourth O2- site, O2- is bonded in a distorted linear geometry to one Nb5+ and one P5+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Assessment of Impurities in Neptunium Metal Using Double-Focusing SF-ICP-MS

In the transmutation process, minor actinides such as neptunium, americium and curium obtained from spent nuclear fuel are incorporated into new fuel that can be placed into a fast reactor, where these elements fission into products with shorter half-lives which reduces the health and safety hazards. In order to better understand the all the involved processes, fundamental physical properties of actinides should be investigated, and for that reason, high-purity materials need to be produced. One of the main challenges in characterizing these materials is the lack of pure metal available for study, and lack of analytical methods to determine the purity. Trans-uranic elements are challenging to study because of the need to be handled in specialized facilities, safeguards concerns and they are not easily purchased and/or produced. High-purity Np metal is being produced at the Materials and Fuels Complex (MFC) of Idaho National Laboratory (INL), in a process of direct oxide reduction developed by Squires and Lessing, with a target purity of 99.999%. The goal of this research is to develop methods to determine the impurities in the Np metal, with detection limits low enough to achieve this purity level. In this work, we have used several ICP-MS and ICP OES techniques, but the focus was the method development using a recently acquired Double-Focusing Sector Field Inductively Coupled Plasma Mass Spectrometer (SF-ICP-MS). To produce the Np metal, approximately 20 g of the neptunium oxide powder was calcined at 800 oC for 6 h in a magnesium oxide crucible, which is placed inside a stainless steel crucible, that goes into the Hot Uniaxial Press (HUP) furnace insert. After the calcining step, the Np oxide was mixed with approximately 9 g of calcium metal and 100 g of ultra-dry calcium chloride. The HUP furnace was heated in a ramp rate of 50 oC min -1 up to 1000 oC. When the reaction mixture reached 850 oC, a tantalum stirrer was activated at 100 rpm. After the tantalum stirrer was removed and the mixture cooled overnight, the MgO crucible was opened with a hammer and chisel to retrieve the Np metal button at the bottom of the reaction mixture. Prior to the dissolution process, the surface contaminants of the sample were removed. The Np button was washed in 10 mL of ultra-pure water for 1 min, with a faint reaction observed on the surface, indicating the presence of Ca metal. The water-washed sample was placed in a tube with 2 M HCl for only 3 s, as a vigorous reaction in the button surface was observed. The leachates were saved for further analysis. The sample was then rinsed with ultra-pure water and air-dried prior to dissolution. The cleaned sample was placed in a PTFE beaker and 25 mL of 6 M HCl and 150 µL of 24 M HF were added. After 10 minutes of reaction, the beaker was placed on a hot plate for 1 h and 30 min, followed by the addition of 1 mL of 16 M HNO3 and allowed to react for a further 1 h and 20 min. The sample was removed from heat and 10 mL of HNO3 16 M was added to react with the HCl. The beaker was covered and left for overnight reaction, producing a solution with approximately 20 mL of final volume. A Quadrupole Inductively Coupled Plasma Mass Spectrometer (Q-ICP-MS, Perkin Elmer ELAN DRC II Q-ICP-MS) was used to obtain qualitative mass spectra for the dissolution blank, each of the leachates and the dissolved sample. In the water leachate spectrum mainly Ca and Mg were observed, while the acid wash had a similar peak pattern to the one observed for the Np metal sample, indicating that the process not only removed surface contamination, but also reacted with the sample itself. In the Np material spectrum, Ta and actinides were identified as candidates for major contaminants, as the most intense peaks corresponded to the mass-to-charge ratios of these elements. Minor contaminants included Al, Au, Ca, Cr, Fe, I, Na, Nb, Pb, Sn, Ti, Tl, V, Y. The presence of impurities in the material could have originated from several sources, such as the materials used for the casting process, the use of impure NpO2 or contamination of reagents and materials used for the analysis. Some of the isotopes listed as potential contaminants are susceptible to spectral interferences, so Double-Focusing SF-ICP-MS (Nu Instruments Attom ES HR-ICP-MS) was used for the quantitative analysis. For each isotope determined, several items were evaluated: raw signal of a blank solution, sensitivity and determination coefficient of calibration curves, possibility of interferences and comparison of results obtained for at least two resolving powers (RP): 300 and 4000. The evaluation of the signal in a blank solution can indicate if a spectral interference from the plasma gas and/or the solvent was successfully resolved (commonly observed for 52Cr+/40Ar12C+, for example). It is important to highlight that a signal reduction is expected when a higher RP is used, as the ion beam transmission is decreased by the use of narrower slits

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Synthesis and Single Crystals of Refractory Oxides of Lanthanides and Thorium

At the completion of this program, we can report that we developed a considerable degree of technical improvements in our ability to perform hydrothermal reactions at high temperatures and pressures. We can now routinely perform reactions at 700-750°C and 200 MPa. Currently we are in the process of exploiting this new technology synthesizing a range of exotic new materials investigating relatively poorly understood materials. Our initial efforts focused on the chemistry of rare earth oxides with tetravalent and pentavalent oxides. We recently published a study of the lanthanides with Nb 5+ and Ta 5+ ions, where we grew oxides such as RENdO 4 and RETaO 4 as high quality single crystals. These compounds were targeted as potential hosts for luminescent and scintillation materials, particularly given that they are among the densest oxide hosts and hence have good potential as absorbers for high energy radiation like X-rays and gamma rays. We also isolated a range of unusual new rare earth tantalates with very complex structures. indicating that the chemistry is very sensitive to conditions. We performed some fairly comprehensive examinations of the solid-state chemistry of rare earth ions with various tetravalent metal ions especially Si 4+ , Ge 4+ , Sn 4+ and Ti 4+ . Given the potential role of rare earth silicates in immobilizing radioactive waste elements in long-term storage, and the similarity of our hydrothermal fluids with known geological conditions, this chemistry continues to be relevant. We prepared an extensive series of new lanthanide germanates (e.g. RE 13 Ge 6 O 31 (OH), BaRE 10 (GeO 4 ) 4 O 8 ). and found that there is there is almost no overlap between the chemistry of the rare earth silicates. Stannic oxide (SnO 2 ) is much more refractory and requires higher temperatures and of mineralizer concentrations. One significant result is the growth of RE 2 Sn 2 O 7 pyrochlore single crystals. These are of interest because the rare earth stannate pyrochlores are known to display a wide range of magnetic frustration such as spin ice behavior. We grew high quality single crystals of rare earth germanate and stannate pyrochlores and this led to a collaboration with Professor Kate Ross at Colorado State. Preliminary measurements, indicate that the crystals contain no detectable defects or site disorder. Initial neutron diffraction on single crystals was performed at Oak Ridge, and more detailed experiments involving the Ross group are underway at both NIST and ORNL. This particular chemistry has turned out to be the most potentially significant work on this project and the collaborative effort with Prof. Ross is the topic of a DoE renewal project on quantum materials. Our initial foray into the hydrothermal chemistry of rare earth titanates has also been very promising and a range of cubic and polar ferroic phases of the light rare earths RE 2 Ti 2 O 7 (RE = La - Pr) in the P2 1 phase. We also discovered an interesting new phase Ce 2 Ti 4 O 11 that can have implications in heavy metal immobilization and storage. along with a series of new rare earth titanates (La 5 Ti 4 O 15 (OH) Sm 3 TiO 5 (OH) 3 and Lu 5 Ti 2 O 11 (OH) with exceptionally complex structures. One interesting sidelight has been high temperature hydrothermal chemistry terbium, including the growth of large crystals of TbO(OH). This is not a new compound but it is the first time it has been grown as large single crystals. The Tb atom density is almost as high as that in Tb 2 O 3 and has a very high Verdet constant (ca. 70), making it a very attractive candidate as a Faraday rotator. Unfortunately it is not in a cubic structure but he material is hard, stable, pure and inexpensive, so should still be an attractive Faraday oscillator. We recently received a patent on this material. We also synthesized K 2 Tb(Ge 2 O 7 ) containing stable octahedral Tb 4+ ions, which appears to be the first example of a well-characterized Tb 4+ complex. Given that Tb 4+ has been proposed as a benign surrogate for more treacherous tetravalent ions such as Cf 4+ and Bk 4+ , we think that Tb 4+ silicates can be a particularly useful study for actinide immobilization and related work. We also began reaction studies with rare earths and both ReO 2 and RuO 2 . These resulted in large single crystals of species like RE 5 Ru 2 O 12 , RE 4 Re 2 O 11 , REReO 4 and RE 2 ReO 5 . Several of these samples have already been sent to ORNL for magnetic and neutron diffraction studies.

36 MATERIALS SCIENCE↗