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At least 415 records · Page 23
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on Ho5Ti5O17 by Materials Project

Ho5Ti5O17 crystallizes in the orthorhombic Pmn2_1 space group. The structure is three-dimensional. there are five inequivalent Ho3+ sites. In the first Ho3+ site, Ho3+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of Ho–O bond distances ranging from 2.24–2.88 Å. In the second Ho3+ site, Ho3+ is bonded in a 9-coordinate geometry to eight O2- atoms. There are a spread of Ho–O bond distances ranging from 2.29–2.73 Å. In the third Ho3+ site, Ho3+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of Ho–O bond distances ranging from 2.28–2.51 Å. In the fourth Ho3+ site, Ho3+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of Ho–O bond distances ranging from 2.21–2.84 Å. In the fifth Ho3+ site, Ho3+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Ho–O bond distances ranging from 2.32–2.54 Å. There are five inequivalent Ti+3.80+ sites. In the first Ti+3.80+ site, Ti+3.80+ is bonded to six O2- atoms to form distorted corner-sharing TiO6 octahedra. The corner-sharing octahedra tilt angles range from 14–38°. There are a spread of Ti–O bond distances ranging from 1.80–2.26 Å. In the second Ti+3.80+ site, Ti+3.80+ is bonded to six O2- atoms to form corner-sharing TiO6 octahedra. The corner-sharing octahedra tilt angles range from 16–40°. There are a spread of Ti–O bond distances ranging from 1.87–2.09 Å. In the third Ti+3.80+ site, Ti+3.80+ is bonded to six O2- atoms to form distorted corner-sharing TiO6 octahedra. The corner-sharing octahedra tilt angles range from 11–40°. There are a spread of Ti–O bond distances ranging from 1.88–2.17 Å. In the fourth Ti+3.80+ site, Ti+3.80+ is bonded to six O2- atoms to form corner-sharing TiO6 octahedra. The corner-sharing octahedra tilt angles range from 11–30°. There are a spread of Ti–O bond distances ranging from 1.91–2.09 Å. In the fifth Ti+3.80+ site, Ti+3.80+ is bonded to six O2- atoms to form corner-sharing TiO6 octahedra. The corner-sharing octahedra tilt angles range from 14–38°. There are a spread of Ti–O bond distances ranging from 1.88–2.19 Å. There are seventeen inequivalent O2- sites. In the first O2- site, O2- is bonded in a 2-coordinate geometry to two Ho3+ and two equivalent Ti+3.80+ atoms. In the second O2- site, O2- is bonded in a distorted T-shaped geometry to one Ho3+ and two equivalent Ti+3.80+ atoms. In the third O2- site, O2- is bonded in a 4-coordinate geometry to two Ho3+ and two equivalent Ti+3.80+ atoms. In the fourth O2- site, O2- is bonded to three Ho3+ and one Ti+3.80+ atom to form corner-sharing OHo3Ti tetrahedra. In the fifth O2- site, O2- is bonded in a 4-coordinate geometry to three Ho3+ and one Ti+3.80+ atom. In the sixth O2- site, O2- is bonded in a 3-coordinate geometry to two Ho3+ and two equivalent Ti+3.80+ atoms. In the seventh O2- site, O2- is bonded in a 2-coordinate geometry to two equivalent Ho3+ and two Ti+3.80+ atoms. In the eighth O2- site, O2- is bonded to two equivalent Ho3+ and two Ti+3.80+ atoms to form distorted corner-sharing OHo2Ti2 tetrahedra. In the ninth O2- site, O2- is bonded in a 4-coordinate geometry to two equivalent Ho3+ and two Ti+3.80+ atoms. In the tenth O2- site, O2- is bonded in a 4-coordinate geometry to two equivalent Ho3+ and two Ti+3.80+ atoms. In the eleventh O2- site, O2- is bonded in a 4-coordinate geometry to two equivalent Ho3+ and two Ti+3.80+ atoms. In the twelfth O2- site, O2- is bonded to two equivalent Ho3+ and two Ti+3.80+ atoms to form distorted corner-sharing OHo2Ti2 tetrahedra. In the thirteenth O2- site, O2- is bonded in a 4-coordinate geometry to three Ho3+ and one Ti+3.80+ atom. In the fourteenth O2- site, O2- is bonded to three Ho3+ and one Ti+3.80+ atom to form corner-sharing OHo3Ti tetrahedra. In the fifteenth O2- site, O2- is bonded in a 4-coordinate geometry to two equivalent Ho3+ and two Ti+3.80+ atoms. In the sixteenth O2- site, O2- is bonded in a 4-coordinate geometry to two equivalent Ho3+ and two Ti+3.80+ atoms. In the seventeenth O2- site, O2- is bonded in a 3-coordinate geometry to two Ho3+ and two equivalent Ti+3.80+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Flame dynamics and kinetic coupling of ammonia and dimethyl-ether in non-premixed cool and warm flames at elevated pressure

Developing advanced low-temperature combustion engines with ammonia-biofuel blends requires a comprehensive understanding of low-temperature flame dynamics and kinetic interactions between ammonia and oxygenated fuels at elevated pressures. This work aims to study the dynamics and kinetics of non-premixed Dimethyl Ether (DME)/Ammonia (NH 3 ) cool and warm flames, and their reignition to hot flames. A counterflow burner is employed to establish DME/NH 3 cool/warm flames at pressures up to 5 atm. The extinction limits of cool flame and the reignition limits of warm flame to hot flame are measured by varying NH 3 concentrations and compared to simulations to quantitatively examine the effects on DME/NH 3 flames. It is found that NH 3 inhibits low-temperature DME oxidation and results in lower cool flame extinction limits. Warm flames in the presence of NH 3 are observed for the first time, revealing a non-monotonic effect of NH 3 addition: a small amount of NH 3 presence enhances warm flame chemistry and promotes reignition to hot flames, while a high NH 3 concentration weakens the warm flame. This trend is further explained by 0-D PSR kinetic simulations and 1-D S-curve flame dynamic calculations. Three flame transition regimes between cool flames (CF), warm flames (WF), and hot flames (HF) by different levels of NH 3 additions at a specific strain rate are identified, namely WFHF reignition, WF-CF transition, and WF extinction. Reaction sensitivity analyses of OH at low temperatures show that NH3 inhibits DME oxidation through OH consumption via H-abstraction and the kinetic couplings of RO 2 /NH 2 , RO 2 /NO x , R/NO x , and O 2 QOOH/NO x further suppress the low-temperature branching. At intermediate-temperatures, NH 2 /NO x /HO 2 coupling promotes warm flames via the pathway NH 2 → H 2 NO → HNO → NO by converting O 2 → HO 2 → OH. At even higher NH₃ concentrations, radical termination reactions of NH 2 + NO/NO 2 and excessive OH consumption via H-abstraction inhibit the flame. The insights into the kinetic coupling between NH 3 and low-temperature chemistry at elevated pressure and its impact on the dynamics of cool-warm-hot flame transitions will contribute to advancing combustion technologies with reduced emissions and improved energy-efficiency.

42 ENGINEERING↗
DOE OSTI2020

Materials Data on CsHoSiS4 by Materials Project

CsHoSiS4 crystallizes in the orthorhombic P2_12_12_1 space group. The structure is three-dimensional. Cs1+ is bonded in a 8-coordinate geometry to eight S2- atoms. There are a spread of Cs–S bond distances ranging from 3.45–3.87 Å. Ho3+ is bonded to seven S2- atoms to form distorted HoS7 pentagonal bipyramids that share corners with two equivalent HoS7 pentagonal bipyramids, a cornercorner with one SiS4 tetrahedra, edges with two equivalent HoS7 pentagonal bipyramids, and edges with three equivalent SiS4 tetrahedra. There are a spread of Ho–S bond distances ranging from 2.78–2.98 Å. Si4+ is bonded to four S2- atoms to form SiS4 tetrahedra that share a cornercorner with one HoS7 pentagonal bipyramid and edges with three equivalent HoS7 pentagonal bipyramids. There are a spread of Si–S bond distances ranging from 2.12–2.15 Å. There are four inequivalent S2- sites. In the first S2- site, S2- is bonded in a 5-coordinate geometry to three equivalent Cs1+, one Ho3+, and one Si4+ atom. In the second S2- site, S2- is bonded in a 4-coordinate geometry to one Cs1+, two equivalent Ho3+, and one Si4+ atom. In the third S2- site, S2- is bonded in a 1-coordinate geometry to two equivalent Cs1+, two equivalent Ho3+, and one Si4+ atom. In the fourth S2- site, S2- is bonded in a 3-coordinate geometry to two equivalent Cs1+, two equivalent Ho3+, and one Si4+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ho3CuSiS7 by Materials Project

Ho3CuSiS7 crystallizes in the hexagonal P6_3 space group. The structure is three-dimensional. Ho3+ is bonded in a 8-coordinate geometry to eight S2- atoms. There are a spread of Ho–S bond distances ranging from 2.75–3.15 Å. Cu1+ is bonded in a trigonal planar geometry to three equivalent S2- atoms. All Cu–S bond lengths are 2.24 Å. Si4+ is bonded in a tetrahedral geometry to four S2- atoms. There are one shorter (2.11 Å) and three longer (2.15 Å) Si–S bond lengths. There are three inequivalent S2- sites. In the first S2- site, S2- is bonded in a 4-coordinate geometry to three equivalent Ho3+ and one Si4+ atom. In the second S2- site, S2- is bonded in a 5-coordinate geometry to four equivalent Ho3+ and one Cu1+ atom. In the third S2- site, S2- is bonded in a distorted tetrahedral geometry to three equivalent Ho3+ and one Si4+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ho3CuSnS7 by Materials Project

Ho3CuSnS7 crystallizes in the hexagonal P6_3 space group. The structure is three-dimensional. Ho3+ is bonded in a 7-coordinate geometry to seven S2- atoms. There are a spread of Ho–S bond distances ranging from 2.72–3.14 Å. Cu1+ is bonded in a trigonal planar geometry to three equivalent S2- atoms. All Cu–S bond lengths are 2.23 Å. Sn4+ is bonded in a tetrahedral geometry to four S2- atoms. There are one shorter (2.41 Å) and three longer (2.42 Å) Sn–S bond lengths. There are three inequivalent S2- sites. In the first S2- site, S2- is bonded in a distorted rectangular see-saw-like geometry to three equivalent Ho3+ and one Sn4+ atom. In the second S2- site, S2- is bonded in a 4-coordinate geometry to three equivalent Ho3+ and one Cu1+ atom. In the third S2- site, S2- is bonded in a tetrahedral geometry to three equivalent Ho3+ and one Sn4+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ho3CuGeS7 by Materials Project

Ho3CuGeS7 crystallizes in the hexagonal P6_3 space group. The structure is three-dimensional. Ho3+ is bonded in a 8-coordinate geometry to eight S2- atoms. There are a spread of Ho–S bond distances ranging from 2.73–3.30 Å. Cu1+ is bonded in a trigonal planar geometry to three equivalent S2- atoms. All Cu–S bond lengths are 2.23 Å. Ge4+ is bonded in a tetrahedral geometry to four S2- atoms. There are one shorter (2.21 Å) and three longer (2.24 Å) Ge–S bond lengths. There are three inequivalent S2- sites. In the first S2- site, S2- is bonded in a 5-coordinate geometry to four equivalent Ho3+ and one Cu1+ atom. In the second S2- site, S2- is bonded in a tetrahedral geometry to three equivalent Ho3+ and one Ge4+ atom. In the third S2- site, S2- is bonded in a distorted rectangular see-saw-like geometry to three equivalent Ho3+ and one Ge4+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ho3CuSiSe7 by Materials Project

Ho3CuSiSe7 crystallizes in the hexagonal P6_3 space group. The structure is three-dimensional. Ho3+ is bonded in a 8-coordinate geometry to eight Se2- atoms. There are a spread of Ho–Se bond distances ranging from 2.87–3.34 Å. Cu1+ is bonded in a trigonal planar geometry to three equivalent Se2- atoms. All Cu–Se bond lengths are 2.36 Å. Si4+ is bonded in a tetrahedral geometry to four Se2- atoms. There are one shorter (2.28 Å) and three longer (2.31 Å) Si–Se bond lengths. There are three inequivalent Se2- sites. In the first Se2- site, Se2- is bonded in a 4-coordinate geometry to three equivalent Ho3+ and one Si4+ atom. In the second Se2- site, Se2- is bonded in a 5-coordinate geometry to four equivalent Ho3+ and one Cu1+ atom. In the third Se2- site, Se2- is bonded in a distorted tetrahedral geometry to three equivalent Ho3+ and one Si4+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on HoInGe2O7 by Materials Project

HoInGe2O7 crystallizes in the monoclinic C2 space group. The structure is three-dimensional. Ho3+ is bonded to six O2- atoms to form distorted HoO6 pentagonal pyramids that share corners with six GeO4 tetrahedra and edges with three equivalent InO6 pentagonal pyramids. There are a spread of Ho–O bond distances ranging from 2.22–2.38 Å. In3+ is bonded to six O2- atoms to form distorted InO6 pentagonal pyramids that share corners with six GeO4 tetrahedra and edges with three equivalent HoO6 pentagonal pyramids. There are a spread of In–O bond distances ranging from 2.18–2.26 Å. There are two inequivalent Ge4+ sites. In the first Ge4+ site, Ge4+ is bonded to four O2- atoms to form GeO4 tetrahedra that share corners with three equivalent HoO6 pentagonal pyramids, corners with three equivalent InO6 pentagonal pyramids, and a cornercorner with one GeO4 tetrahedra. There are a spread of Ge–O bond distances ranging from 1.76–1.78 Å. In the second Ge4+ site, Ge4+ is bonded to four O2- atoms to form GeO4 tetrahedra that share corners with three equivalent HoO6 pentagonal pyramids, corners with three equivalent InO6 pentagonal pyramids, and a cornercorner with one GeO4 tetrahedra. There is one shorter (1.77 Å) and three longer (1.78 Å) Ge–O bond length. There are eight inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted trigonal planar geometry to one Ho3+, one In3+, and one Ge4+ atom. In the second O2- site, O2- is bonded in a distorted trigonal planar geometry to one Ho3+, one In3+, and one Ge4+ atom. In the third O2- site, O2- is bonded in a linear geometry to two equivalent Ge4+ atoms. In the fourth O2- site, O2- is bonded in a bent 150 degrees geometry to two equivalent Ge4+ atoms. In the fifth O2- site, O2- is bonded in a distorted trigonal planar geometry to one Ho3+, one In3+, and one Ge4+ atom. In the sixth O2- site, O2- is bonded in a distorted trigonal planar geometry to one Ho3+, one In3+, and one Ge4+ atom. In the seventh O2- site, O2- is bonded in a distorted trigonal planar geometry to one Ho3+, one In3+, and one Ge4+ atom. In the eighth O2- site, O2- is bonded in a 3-coordinate geometry to one Ho3+, one In3+, and one Ge4+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on HoPS4 by Materials Project

HoPS4 is Zircon-like structured and crystallizes in the tetragonal I4_1/acd space group. The structure is three-dimensional. there are two inequivalent Ho3+ sites. In the first Ho3+ site, Ho3+ is bonded in a 8-coordinate geometry to eight S2- atoms. There are four shorter (2.82 Å) and four longer (2.99 Å) Ho–S bond lengths. In the second Ho3+ site, Ho3+ is bonded in a distorted body-centered cubic geometry to eight S2- atoms. All Ho–S bond lengths are 2.90 Å. P5+ is bonded in a tetrahedral geometry to four S2- atoms. There are two shorter (2.04 Å) and two longer (2.05 Å) P–S bond lengths. There are two inequivalent S2- sites. In the first S2- site, S2- is bonded in a 3-coordinate geometry to two Ho3+ and one P5+ atom. In the second S2- site, S2- is bonded in a distorted T-shaped geometry to two Ho3+ and one P5+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ho2WO6 by Materials Project

Ho2WO6 crystallizes in the monoclinic C2/c space group. The structure is three-dimensional. there are three inequivalent Ho3+ sites. In the first Ho3+ site, Ho3+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Ho–O bond distances ranging from 2.21–2.77 Å. In the second Ho3+ site, Ho3+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Ho–O bond distances ranging from 2.27–2.46 Å. In the third Ho3+ site, Ho3+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Ho–O bond distances ranging from 2.18–2.62 Å. W6+ is bonded in a distorted trigonal bipyramidal geometry to five O2- atoms. There are a spread of W–O bond distances ranging from 1.84–2.11 Å. There are six inequivalent O2- sites. In the first O2- site, O2- is bonded in a 3-coordinate geometry to two equivalent Ho3+ and one W6+ atom. In the second O2- site, O2- is bonded to four Ho3+ atoms to form a mixture of corner and edge-sharing OHo4 tetrahedra. In the third O2- site, O2- is bonded in a distorted trigonal non-coplanar geometry to two equivalent Ho3+ and one W6+ atom. In the fourth O2- site, O2- is bonded to three Ho3+ and one W6+ atom to form a mixture of corner and edge-sharing OHo3W tetrahedra. In the fifth O2- site, O2- is bonded in a 3-coordinate geometry to two equivalent Ho3+ and one W6+ atom. In the sixth O2- site, O2- is bonded in a 2-coordinate geometry to three Ho3+ and one W6+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on HoAsO4 by Materials Project

HoAsO4 is Zircon-like structured and crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. Ho3+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Ho–O bond distances ranging from 2.32–2.52 Å. As5+ is bonded in a tetrahedral geometry to four O2- atoms. There is three shorter (1.72 Å) and one longer (1.73 Å) As–O bond length. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a 3-coordinate geometry to two equivalent Ho3+ and one As5+ atom. In the second O2- site, O2- is bonded in a 3-coordinate geometry to two equivalent Ho3+ and one As5+ atom. In the third O2- site, O2- is bonded in a 3-coordinate geometry to two equivalent Ho3+ and one As5+ atom. In the fourth O2- site, O2- is bonded in a distorted trigonal planar geometry to two equivalent Ho3+ and one As5+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on HoFeGe2O7 by Materials Project

HoFeGe2O7 crystallizes in the monoclinic P2_1/m space group. The structure is three-dimensional. Ho3+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Ho–O bond distances ranging from 2.22–2.43 Å. Fe3+ is bonded to six O2- atoms to form distorted FeO6 octahedra that share corners with four GeO4 tetrahedra and an edgeedge with one FeO6 octahedra. There are a spread of Fe–O bond distances ranging from 1.99–2.16 Å. There are four inequivalent Ge4+ sites. In the first Ge4+ site, Ge4+ is bonded to four O2- atoms to form GeO4 tetrahedra that share corners with four equivalent FeO6 octahedra. The corner-sharing octahedra tilt angles range from 45–54°. There are a spread of Ge–O bond distances ranging from 1.78–1.80 Å. In the second Ge4+ site, Ge4+ is bonded in a 4-coordinate geometry to five O2- atoms. There are a spread of Ge–O bond distances ranging from 1.75–2.37 Å. In the third Ge4+ site, Ge4+ is bonded in a 4-coordinate geometry to five O2- atoms. There are a spread of Ge–O bond distances ranging from 1.75–2.40 Å. In the fourth Ge4+ site, Ge4+ is bonded to four O2- atoms to form GeO4 tetrahedra that share corners with four equivalent FeO6 octahedra. The corner-sharing octahedra tilt angles range from 45–54°. There are a spread of Ge–O bond distances ranging from 1.78–1.80 Å. There are ten inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted trigonal non-coplanar geometry to one Ho3+, one Fe3+, and one Ge4+ atom. In the second O2- site, O2- is bonded in a distorted trigonal non-coplanar geometry to one Ho3+, one Fe3+, and one Ge4+ atom. In the third O2- site, O2- is bonded in a 3-coordinate geometry to one Ho3+, one Fe3+, and one Ge4+ atom. In the fourth O2- site, O2- is bonded in a bent 150 degrees geometry to two Ge4+ atoms. In the fifth O2- site, O2- is bonded in a bent 150 degrees geometry to two Ge4+ atoms. In the sixth O2- site, O2- is bonded in a 4-coordinate geometry to two equivalent Fe3+ and two Ge4+ atoms. In the seventh O2- site, O2- is bonded in a distorted trigonal planar geometry to two equivalent Ho3+ and one Ge4+ atom. In the eighth O2- site, O2- is bonded in a distorted trigonal planar geometry to two equivalent Ho3+ and one Ge4+ atom. In the ninth O2- site, O2- is bonded in a 4-coordinate geometry to two equivalent Fe3+ and two Ge4+ atoms. In the tenth O2- site, O2- is bonded in a 3-coordinate geometry to one Ho3+, one Fe3+, and one Ge4+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on HoTaO4 by Materials Project

HoTaO4 crystallizes in the monoclinic P2/c space group. The structure is three-dimensional. Ho3+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Ho–O bond distances ranging from 2.28–2.56 Å. Ta5+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Ta–O bond distances ranging from 1.89–2.22 Å. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a 3-coordinate geometry to two equivalent Ho3+ and one Ta5+ atom. In the second O2- site, O2- is bonded in a 4-coordinate geometry to two equivalent Ho3+ and two equivalent Ta5+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on HoSeClO3 by Materials Project

HoSeO3Cl crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. Ho3+ is bonded to five O2- and two equivalent Cl1- atoms to form a mixture of distorted corner and edge-sharing HoCl2O5 pentagonal bipyramids. There are a spread of Ho–O bond distances ranging from 2.20–2.37 Å. There are one shorter (2.74 Å) and one longer (2.76 Å) Ho–Cl bond lengths. Se4+ is bonded in a distorted trigonal non-coplanar geometry to three O2- atoms. There is one shorter (1.70 Å) and two longer (1.75 Å) Se–O bond length. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a bent 150 degrees geometry to one Ho3+ and one Se4+ atom. In the second O2- site, O2- is bonded in a 3-coordinate geometry to two equivalent Ho3+ and one Se4+ atom. Cl1- is bonded in a bent 150 degrees geometry to two equivalent Ho3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Thermal Stability and Decomposition Products of P-Doped Ferrihydrite

This work aimed to determine the effect of various amounts of P admixtures in synthetic ferrihydrite on its thermal stability, transformation processes, and the properties of the products, at a broad range of temperatures up to 1000 °C. A detailed study was conducted using a series of synthetic ferrihydrites Fe 5 HO 8 ·4H 2 O doped with phosphates at P/Fe molar ratios of 0.2, 0.5, and 1.0. Ferrihydrite was synthesized by a reaction of Fe 2 (SO 4 ) 3 with 1 M KOH at room temperature in the presence of K 2 HPO 4 at pH 8.2. The products of the synthesis and the products of heating were characterized at various stages of transformation by using differential thermal analysis accompanied with X-ray diffraction, Fourier transform infrared spectroscopy, and scanning electron microscopy-energy dispersive X-ray spectroscopy. Coprecipitation of P with ferrihydrite results in the formation of P-doped 2-line ferrihydrite. A high P content reduces crystallinity. Phosphate significantly inhibits the thermal transformation processes. The temperature of thermal transformation increases from below 550 to 710–750 °C. Formation of intermediate maghemite and Fe-phosphates, is observed. The product of heating up to 1000 °C contains hematite associated with rodolicoite FePO 4 and grattarolaite Fe 3 PO 7 . Higher P content greatly increases the thermal stability and transformation temperature of rodolicoite as well.

thermal transformations↗
DOE OSTI2020

Materials Data on HoNbO4 by Materials Project

HoNbO4 crystallizes in the monoclinic C2/c space group. The structure is three-dimensional. Ho3+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Ho–O bond distances ranging from 2.32–2.41 Å. Nb5+ is bonded to six O2- atoms to form distorted edge-sharing NbO6 tetrahedra. There are a spread of Nb–O bond distances ranging from 1.88–2.50 Å. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a 3-coordinate geometry to two equivalent Ho3+ and one Nb5+ atom. In the second O2- site, O2- is bonded in a 4-coordinate geometry to two equivalent Ho3+ and two equivalent Nb5+ atoms.

36 MATERIALS SCIENCE↗