Structure of new metastable cubic TbO2−x

Ahmadpour, Faraz; Mozharivskyj, Yurij

doi:10.1016/j.jallcom.2006.11.018

Cited by 5 publications

(3 citation statements)

References 13 publications

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“…Such a filled bixbyite structure type was already reported for e.g. Ce x RE 2– x O 3+ x /2 , − Tb 2 O 3+ x (16 c partially occupied), or as antitype in Li 3 ScN 2 and Li 3 AlN 2 (fully occupied 16 c ). , The compound did not decompose upon exposure in air for 2 days (Figure S1). Sodium fluoride, NaF, could be completely removed by washing in methanol.…”

Section: Resultssupporting

confidence: 77%

“…They may be described as stuffed variants of the bixbyite type, where the crystallographic position 16c is additionally occupied. In the UN 1.6 type it is partially occupied, e.g., in superstoichiometric lanthanide oxides like Tb 2 O 3+x 48,49 and in uranium nitrides U 2 N 3−x . 58 In SmH 0.782 (11) OF 0.218 (11) the 16c position is completely filled.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

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From SmOF to SmH_0.78OF_0.22: H/F Substitution in Oxide Fluorides as a Synthesis Route to Heteroanionic Compounds

2021

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Mixed anionic hydrides of the rare earths are a fascinating class of compounds as potential functional materials, especially in luminescence, as photochromic thin films and for ion conduction. For exploratory studies, the effectiveness of various synthesis methods must be investigated, which is done here for metathesis reactions. The reaction of Sm2O3 with PTFE yields SmOF (P21/c, a = 5.60133(19) Å, b = 5.65567(19) Å, c = 5.6282(2) Å, β = 90.169(5)°, V = 178.295(11) Å3, and Z = 4) in a new, probably metastable, polymorph of the baddeleyite-type structure. Metathesis reactions of SmOF with LiH, NaH, or CaH2 led to a samarium hydride oxide fluoride, SmH x OF1–x ; i.e., incomplete H/F exchange occurs. X-ray diffraction and neutron diffraction on a compound with x = 0.78 obtained via NaH reveal hydride, oxide, and fluoride ions to be partially ordered. SmH0.78OF0.22 (Ia3̅, a = 10.947(2) Å, V = 1311.7(4) Å3, Z = 32) crystallizes in an anti-Li3AlN2-type structure with distorted cubic anion coordination for samarium atoms (site symmetry 3̅ and 2) and distorted tetrahedral arrangement of samarium atoms around the anions (site symmetry 1 and 3). It is a fully structurally characterized hydride oxide fluoride and shows a rare crystal chemical featurethe occupation of a crystallographic site by three different anions (0.188 H + 0.667 O + 0.145 F). Interatomic distances between samarium and hydrogen and samarium and the mixed hydrogen/oxygen/fluorine site range from 2.45 to 2.48 Å and 2.29 to 2.42 Å, respectively, and are similar to those in samarium hydride, samarium oxide, and samarium fluoride. Fluoride extraction by reaction with alkali and alkaline earth hydrides has thus proven to be a useful synthesis route to hydride oxides and also hydride oxide halogenides, which might be further exploited in exploratory research on heteroanionic metal hydrides.

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Section: Resultssupporting

confidence: 77%

Section: ■ Results and Discussionmentioning

confidence: 99%

From SmOF to SmH_0.78OF_0.22: H/F Substitution in Oxide Fluorides as a Synthesis Route to Heteroanionic Compounds

2021

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“…As known, TbO 2 (the limiting case of Ce1-cTbcO 2 for c=1) could be non-stoichiometric on oxygen sub-lattice which leads to symmetry reduction and, very much likely, two types of Tb ions, in both oxidation states 3+ and 4+ [31,32]. We do not consider nonstoichiometric TbO 2 in the present study, focusing on the oxidation state 4+ used in our thermodynamic analysis.…”

Section: Computational Methods and Basic Properties Of Cementioning

confidence: 99%

Dopant solubility in ceria: alloy thermodynamics combined with the DFT+U calculations

et al. 2018

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Tb-doped CeO 2 (ceria) is a promising mixed conductor for oxygen permeation membranes and reversible oxygen sorbents. To predict solubility of Tb ions in ceria for a wide range of concentrations, density functional theory (DFT+U) calculations with two different values of Hubbard U-parameter on Tb and Ce ions were combined with alloy thermodynamics and the Concentration Wave approach. It is shown that, to predict properties of disordered solid solutions at finite temperatures, the energy parameters in the mixing energies can be extracted from the DFT+U calculations performed at T=0 K for two ordered configurations of the dopant in the supercells. The unlimited solubility of Tb 4+ in CeO 2 in the quasi-binary cross-section CeO 2-TbO 2 is predicted in the temperature range where both stoichiometric TbO 2 and CeO 2 reveal fluoride structures (above 700 o C).

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The High‐Pressure Oxide Tb₃O₅ and its Non‐Centrosymmetric Low‐Temperature Polymorph–A Comprehensive Study

Glätzle

Janka

Svitlyk

et al. 2018

Chemistry A European J

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In this article, the first thoroughly characterized mixed‐valent binary rare earth oxide synthesized under high‐pressure/high‐temperature conditions, and its low‐temperature polymorph are reported. Crystalline HT‐HP‐Tb3O5 has been prepared from an equimolar mixture of Tb4O7 and Tb2O3 under reaction conditions of 8 GPa and 1323 K. Single‐crystal X‐ray structure determination showed that HT‐HP‐Tb3O5 crystallizes in the orthorhombic space group Pnma, isopointal to the β‐Yb5Sb3‐type structure. Temperature‐dependent measurements of the magnetic susceptibility showed that HT‐HP‐Tb3O5 is a Curie–Weiss paramagnet. The observed effective magnetic moment of μ eff=9.21(2) μ B per formula unit fits well to the calculated moment of μ calc=9.17 μ B. Low‐field measurements revealed antiferromagnetic ordering at T N=3.6(1) K. Heat capacity measurements indicated an intrinsic structural phase transition of HT‐HP‐Tb3O5 at low temperature, which was confirmed by synchrotron X‐ray powder diffraction data recorded at 2 K. The metastable high‐pressure modification HT‐HP‐Tb3O5 undergoes a translationengleiche transition from space group Pnma to Pn21 a (non‐standard setting of Pna21), leading to the low‐temperature polymorph LT‐HP‐Tb3O5 by loss of a mirror plane (displacive phase transition).

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Structure of new metastable cubic TbO2−x

Cited by 5 publications

References 13 publications

From SmOF to SmH_0.78OF_0.22: H/F Substitution in Oxide Fluorides as a Synthesis Route to Heteroanionic Compounds

From SmOF to SmH_0.78OF_0.22: H/F Substitution in Oxide Fluorides as a Synthesis Route to Heteroanionic Compounds

Dopant solubility in ceria: alloy thermodynamics combined with the DFT+U calculations

The High‐Pressure Oxide Tb₃O₅ and its Non‐Centrosymmetric Low‐Temperature Polymorph–A Comprehensive Study

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Structure of new metastable cubic TbO2−x

Cited by 5 publications

References 13 publications

From SmOF to SmH0.78OF0.22: H/F Substitution in Oxide Fluorides as a Synthesis Route to Heteroanionic Compounds

From SmOF to SmH0.78OF0.22: H/F Substitution in Oxide Fluorides as a Synthesis Route to Heteroanionic Compounds

Dopant solubility in ceria: alloy thermodynamics combined with the DFT+U calculations

The High‐Pressure Oxide Tb3O5 and its Non‐Centrosymmetric Low‐Temperature Polymorph–A Comprehensive Study

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From SmOF to SmH_0.78OF_0.22: H/F Substitution in Oxide Fluorides as a Synthesis Route to Heteroanionic Compounds

From SmOF to SmH_0.78OF_0.22: H/F Substitution in Oxide Fluorides as a Synthesis Route to Heteroanionic Compounds

The High‐Pressure Oxide Tb₃O₅ and its Non‐Centrosymmetric Low‐Temperature Polymorph–A Comprehensive Study