Browsing by Author "Locke, Ralf J. C."

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Open Access
Ba7C2Al2O9 : a barium oxide carbide oxoaluminate with the structured formula Ba7O[C2][AlO4]2
(2025) Reckeweg, Olaf; Lissner, Falk; Locke, Ralf J. C.; Schleid, Thomas
The mixed‐anionic barium compound Ba7O[C2][AlO4]2 is obtained by serendipity via a high‐temperature synthesis route designed to yield “Ba5[AlC2]2”. Its new crystal structure is determined from X‐ray diffraction data of selected single crystals exhibiting the orthorhombic space group Pnma with the lattice parameters a = 2264.21(16), b = 597.08(4), and c = 1114.67(8) pm for Z = 4. Isolated [AlO4]5- tetrahedra alongside O2- and [C2]2- anions provide appropriate coordination spheres for the seven crystallographically independent Ba2+ cations with C.N. = 7-9. These structural elements and their incremental volumes are compared to those of related compounds. Irregular [OBa5+1]10+ octahedra and ([C2]Ba5+2)12+ polyhedra complete the crystal structure of Ba7O[C2][AlO4]2, whose most covalent features (ortho‐oxoaluminate tetrahedra [AlO4]5- and acetylide dumbbells -[C≡C]-) can also be identified unambiguously by single‐crystal Raman spectroscopy.
Open Access
The first members of the monoclinic lanthanoid(III) fluoride oxoarsenate(III) series Ln2F2[As2O5] (Ln=La - Nd and Sm)
(2025) Locke, Ralf J. C.; Zimmer, Frank C.; Schleid, Thomas
In synthesis experiments for the preparation of Ln5F3[AsO3]4 representatives in evacuated glassy silica ampoules at temperatures of maximum 825 °C, surprisingly compounds with the composition Ln2F2[As2O5] could be obtained and subsequently also reproduced on target. The new Ln2F2[As2O5] representatives with Ln = La - Nd and Sm crystallize needle‐shaped in the monoclinic space group P21/c with lattice parameters ranging from a = 793.24(5) pm, b = 1346.39(9) pm, c = 1359.41(9) pm and β = 106.932(3)° for La2F2[As2O5] to a = 769.11(5) pm, b = 1307.50(9) pm, c = 1328.74(9) pm and β = 106.819(3)° for Sm2F2[As2O5] with Z = 8. Their crystal structure can be broken down into two parts consisting of infinite [Ln2F2]4+ and discrete [As2O5]4− units. Three distinct kinds of fluoride anions are trigonally planar surrounded by lanthanoid cations and another one carries even a fourth of them in their coordination sphere with a secondary contact resulting in a distorted tetrahedron. These [FLn3]8+ and [FLn3+1]11+ building blocks share common corners and edges creating strands {[F2Ln2]4+}, which propagate along [100]. The four different As3+ lone‐pair cations form ψ1‐tetrahedra [AsO3]3− with three oxygen atoms and are conversurally linked pairwisely creating dinuclear pyroanionic [As2O5]4− units. These [As2O5]4− groups arrange themselves alternatingly along [100] with their lone pairs pointing into central empty channels. The {[F2Ln2]4+} strands are linked to the [As2O5]4− units via four distinguishable Ln3+ cations providing them coordination numbers of eight and nine. Raman spectroscopy confirmed that no (OH)− groups resulting from the synthesis were present apt to replace part of the F− and the stoichiometry Ln2F2[As2O5] was verified using WDXS elemental analyses.
Open Access
Luminescence properties of Y3F[Si3O10]:Ln3+ (Ln = Eu, Tb, Er) with thalenite-type host lattice and crystal structure of Tm3F[Si3O10]
(2023) Schäfer, Marion C.; Petter, Michael; Hartenbach, Ingo; Locke, Ralf J. C.; Zhang, Shuang; Wickleder, Claudia; Schleid, Thomas
With Tm3F[Si3O10], a new representative of the Ln3F[Si3O10] series could be synthesized by the reaction of Tm2O3, TmF3 and SiO2 (molar ratio: 1:1:3), applying an excess of CsBr as a fluxing agent in gas-tightly sealed platinum crucibles for eight days at 750 °C, and designed to yield Tm3F3[Si3O9] or Cs2TmF[Si4O10]. Single crystals of Tm3F[Si3O10] (monoclinic, P21/n; a = 725.04(6), b = 1102.43(9), c = 1032.57(8) pm, β = 97.185(7)°; Z = 4) appear as pale celadon, transparent, air- and water-resistant rhombic plates. According to its thalenite-type structure, Tm3F[Si3O10] contains catena-trisilicate anions [Si3O10]8− and triangular [FTm3]8+ cations. The three crystallographically different Tm3+ cations are coordinated by seven plus one (Tm1) or only seven anions (Tm2 and Tm3) exhibiting a single F- anion for each polyhedron, additional to the majority of O2- anions. Furthermore, the luminescence properties of the isotypic colorless compound Y3F[Si3O10] doped with Eu3+ (red emission), Tb3+ (green emission) and Er3+ (yellow and infrared emission), respectively, are reported in presenting their different excitation and emission spectra.
Open Access
Single crystals of EuScCuSe3 : synthesis, experimental and DFT investigations
(2023) Grigoriev, Maxim V.; Ruseikina, Anna V.; Chernyshev, Vladimir A.; Oreshonkov, Aleksandr S.; Garmonov, Alexander A.; Molokeev, Maxim S.; Locke, Ralf J. C.; Elyshev, Andrey V.; Schleid, Thomas
EuScCuSe3 was synthesized from the elements for the first time by the method of cesium-iodide flux. The crystal belongs to the orthorhombic system (Cmcm) with the unit cell parameters a = 3.9883(3) Å, b = 13.2776(9) Å, c = 10.1728(7) Å, V = 538.70(7) Å3. Density functional (DFT) methods were used to study the crystal structure stability of EuScCuSe3 in the experimentally obtained Cmcm and the previously proposed Pnma space groups. It was shown that analysis of elastic properties as Raman and infrared spectroscopy are powerless for this particular task. The instability of EuScCuSe3 in space group Pnma space group is shown on the basis of phonon dispersion curve simulation. The EuScCuSe3 can be assigned to indirect wide-band gap semiconductors. It exhibits the properties of a soft ferromagnet at temperatures below 2 K.
Open Access
Syntheses and patterns of changes in structural parameters of the new quaternary tellurides EuRECuTe3 (RE = Ho, Tm, and Sc) : experiment and theory
(2024) Ruseikina, Anna V.; Grigoriev, Maxim V.; Locke, Ralf J. C.; Chernyshev, Vladimir A.; Schleid, Thomas
The layered orthorhombic quaternary tellurides EuRECuTe3 (RE = Ho, Tm, Sc) with Cmcm symmetry were first synthesized. Single crystals of the compounds up to 500 μm in size were obtained by the halide-flux method at 1120 K from elements taken in a ratio of Eu/RE/Cu/Te = 1:1:1:3. In the series of compounds, the changes in lattice parameters were in the ranges a = 4.3129(3)-4.2341(3) Å, b = 14.3150(9)-14.1562(9) Å, c = 11.2312(7)-10.8698(7) Å, V = 693.40(8)-651.52(7) Å3. In the structures, the cations Eu2+, RE3+ (RE = Ho, Tm, Sc), and Cu+ occupied independent crystallographic positions. The structures were built with distorted copper tetrahedra forming infinite chains [CuTe4]7− and octahedra [RETe6]9- forming two-dimensional layers along the a-axis. These coordination polyhedra formed parallel two-dimensional layers CuRETe32-∞2. Between the layers, along the a-axis, chains of europium trigonal prisms [EuTe6]10- were located. Regularities in the variation of structural parameters and the degree of distortion of coordination polyhedra depending on the ionic radius of the rare-earth metal in the compounds EuRECuCh3 (RE = Ho, Er, Tm, Lu, Sc; Ch = S, Se, Te) were established. It is shown that with a decrease in the ionic radius ri(RE3+) in the compounds EuRECuTe3, the unit-cell volume, bond length d(RE-Te), distortion degree [CuTe4]7-, and crystallographic compression of layers [RECuTe3]2- decreased. The distortion degree of tetrahedral polyhedra [CuCh4]7-, as well as the structural parameters in europium rare-earth copper tellurides EuRECuTe3, were higher than in isostructural quaternary chalcogenides. Ab initio calculations of the crystalline structure, phonon spectrum, and elastic properties of compounds EuRECuTe3 (RE = Ho, Tm, and Sc) ere conducted. The types and wave numbers of fundamental modes were determined, and the involvement of ions in IR and Raman modes was assessed. The calculated data of the crystal structure correlated well with the experimental results.
Open Access
Synthesis, crystal structure and properties of the new laminar quaternary tellurides SrLnCuTe3 (Ln = Sm, Gd-Tm and Lu)
(2023) Ruseikina, Anna V.; Grigoriev, Maxim V.; Molokeev, Maxim S.; Garmonov, Alexander A.; Elyshev, Andrey V.; Locke, Ralf J. C.; Schleid, Thomas
This paper reports for the first time on the new laminar quaternary orthorhombic heterometallic quaternary tellurides SrLnCuTe3, the fabrication of which has been a challenge until this work. Data on the crystal structure of tellurides complete the series of quaternary strontium chalcogenides SrLnCuCh3 (Ch = S, Se, Te). Single crystals of the compounds were synthesized from the elements by the halogenide-flux method at 1070 K. The compounds are crystallizing in two space groups Pnma (Ln = Sm, Gd and Tb) and Cmcm (Ln = Dy-Tm and Lu). For SrSmCuTe3 (a = 11.4592(7), b = 4.3706(3), c = 14.4425(9) Å, space group: Pnma) with the largest lanthanoid cation, Sr2+ shows C.N. = 7, whereas Sm3+ reveals a diminished coordination number C.N. = 6. For SrLuCuTe3 (a = 4.3064(3), b = 14.3879(9), c = 11.1408(7) Å, space group: Cmcm) with the smallest lanthanoid cation, coordination numbers of six are realized for both high-charged cations (Sr2+ and Lu3+: C.N. = 6). The cations Sr2+, Ln3+, Cu+ each take independent positions. The structures are built by distorted [CuTe4]7- tetrahedra, forming the infinite chains {∞1[Cu(Te1)1/1t(Te2)1/1t(Te3)2/2e]5−} along [010] in SrLnCuTe3 (Ln = Sm, Gd and Tb) and [100] in SrLnCuTe3 (Ln = Dy-Tm and Lu). The distortion of the polyhedra [CuTe4]7- was compared for the whole series SrLnCuTe3 by means of τ4-descriptor for the four coordinating Te2- anions, which revealed a decrease in the degree of distortion with a decreasing radius at Ln3+. The distorted octahedra [LnTe6]9- form layers {∞2[Ln(Te1)2/2(Te2)2/2(Te3)2/2]3−}. The distorted octahedra and tetrahedra fuse to form parallel layers {∞2[CuLnTe3]2−} and between them, the Sr2+ cations providing three-dimensionality of the structure are located. In the SrLnCuTe3 (Ln = Sm, Gd and Tb) structures, the Sr2+ cations center capped the trigonal prisms [SrTe6+1]12−, united in infinite chains {∞1[Sr(Te1)2/2(Te2)3/3(Te3)2/2]4−} along the [100] direction. The domains of existence of the Ba2MnS3, BaLaCuS3, Eu2CuS3 and KZrCuS3 structure types are defined in the series of orthorhombic chalcogenides SrLnCuCh3 (Ch = S, Se and Te). The tellurides SrLnCuTe3 (Ln = Tb-Er) of both structure types in the temperature range from 2 up to 300 K are paramagnetic, without showing clear signs of a magnetic phase transition.
Open Access
Synthesis, crystal structure, and optical and magnetic properties of the new quaternary erbium telluride EuErCuTe3 : experiment and calculation
(2024) Ruseikina, Anna V.; Grigoriev, Maxim V.; Locke, Ralf J. C.; Chernyshev, Vladimir A.; Garmonov, Alexander A.; Schleid, Thomas
This paper reports for the first time on a new layered magnetic heterometallic erbium telluride EuErCuTe3. Single crystals of the compound were obtained from the elements at 1120 K using CsI as a flux. The crystal structure of EuErCuTe3 was solved in the space group Cmcm (a = 4.3086(3) Å, b = 14.3093(9) Å, and c = 11.1957(7) Å) with the KZrCuS3 structure type. In the orthorhombic structure of erbium telluride, distorted octahedra ([ErTe6]9−) form two-dimensional layers (Er(Te1)2/2e(Te2)4/2k-)∞2, while distorted tetrahedra ([CuTe4]7-) form one-dimensionally connected substructures (Cu(Te1)2/2e(Te2)2/1t5-∞1) along the [100] direction. The distorted octahedra and tetrahedra form parallel two-dimensional layers (CuErTe32-∞2) between which Eu2+ ions are located in a trigonal-prismatic coordination environment (EuTe610-). The trigonal prisms are connected by faces, forming chains (Eu(Te1)2/2(Te2)4/22-∞1) along the [100] direction. Regularities in the variations in structural parameters were established in the series of erbium chalcogenides (EuErCuCh3 with Ch = S, Se, and Te) and tellurides (EuLnCuTe3 with Ln = Gd, Er, and Lu). Ab-initio calculations of the crystal structure, phonon spectrum, and elastic properties of the compound EuErCuTe3 were performed. The types and wavenumbers of fundamental modes were determined, and the involvement of ions in the IR and Raman modes was assessed. The experimental Raman spectra were interpreted. The telluride EuErCuTe3 at temperatures below 4.2 K was ferrimagnetic, as were the sulfide and selenide derivatives (EuErCuCh3 with Ch = S and Se). Its experimental magnetic characteristics were close to the calculated ones. The decrease in the magnetic phase transition temperature in the series of the erbium chalcogenides was discovered.
Open Access
Theoretical and experimental studies of the structural chameleon EuYCuTe3
(2025) Ruseikina, Anna V.; Grigoriev, Maxim V.; Chernyshev, Vladimir A.; Roginskii, Evgenii M.; Garmonov, Alexander A.; Locke, Ralf J. C.; Schleid, Thomas
Layered orthorhombic single crystals of EuYCuTe3 are synthesized using the ampoule method from the elemental precursors taken in the ratio of 1 Eu:1 Y:1 Cu:3 Te by heating up to 1120 K with an excess of CsI as flux. The orthorhombic structure of EuYCuTe3 is established, and structural parameters are obtained using X-ray diffraction. At ambient conditions, the sample crystallizes in the space group Pnma with the unit cell parameters a = 11.2730(7) Å, b = 4.3214(3) Å, c = 14.3271(9) Å. The structure is composed of vertex-connected [CuTe4]7- tetrahedra, which form chains along the [010] direction, and of edge-connected [YTe6]9- octahedra, which form layers parallel to the (010) plane. The Eu2+ cations are found in a capped trigonal prismatic coordination of Te2- anions. The structural phase transition from the α to the β phase is discovered upon heating the sample to 323 K, which comes accompanied with a decrease of [CuTe4]7- tetrahedral distortion. The symmetry of the high-temperature phase is established as ordered in the space group Cmcm (a = 4.3231(3) Å, b = 14.3328(9) Å, c = 11.2843(7) Å). The nature and microscopic mechanism of the phase transition is discussed. By cooling it down below 3 K, the soft ferromagnetic properties of EuYCuTe3 are discovered. The correlation of the ferromagnetic transition temperature in the series of chalcogenides EuYCuCh3 (Ch = S, Se, Te) with the ionic radius of the chalcogenide anion is established. The structural dynamical elastic properties of α- and β-EuYCuTe3 were calculated within the ab initio approach. The vibrational mode frequencies and decomposition on irreducible representations, as well as the degree of ion involvement in each mode, were determined. The calculations reveal an imaginary mode in the Y-point of the Brillouin zone in the high symmetry β-EuYCuTe3 phase. This finding explains the nature of structural reconstruction in EuYCuTe3 crystal as a second-order phase transition induced by soft mode condensation at the edge of the Brillouin zone. The exfoliation of a single layer is simulated theoretically. The exfoliation energy is estimated, and the dynamical properties of EuYCuTe3 single layers are studied.
Open Access
Three new lanthanum oxoantimonate(III) halides : synthesis and crystal structure of La5Cl3[SbO3]4, La2Sb12O19Br4 and La2Sb12O19I4
(2023) Locke, Ralf J. C.; Bozenhardt, Kim-Natalie; Goerigk, Felix C.; Schleid, Thomas
It was possible to synthesize colorless single crystals of La5Cl3[SbO3]4 (block-shaped) as well as La2Sb12O19Br4 and LaSb12O19I4 (both needle-shaped), representing three new compounds from the system of lanthanum oxoantimonate(III) halides, which have not been described in the literature before. La5Cl3[SbO3]4 crystallizes in the monoclinic space group P2/c with the lattice parameters a = 895.82(5) pm, b = 564.28(3) pm, c = 1728.19(9) pm, and β = 90.007(2)° for Z = 2. This layered compound contains isolated ψ1-tetrahedral [SbO3]3- units, square hemiprisms [LaO8]13-, and antiprisms [LaO4Cl4]9-, La2Sb12O19Br4 and LaSb12O19I4 crystallize isotypically in the orthorhombic space group Pnma with a = 3184.69(19) pm, b = 417.78(3) pm, c = 1019.85(6) pm for the bromide and a = 3215.08(19) pm, b = 419.94(3) pm, c = 1062.89(6) pm for the iodide. Instead of isolated [SbO3]3- anions, semi-tubular features 1∞{[Sb12O19]2-} are present, which consist mainly of [SbO4]5- and few [SbO3]3- units with stereochemically active electronic lone pairs at their Sb3+ centers. Within these so-called “double-halfpipes”, La3+ is surrounded by nine oxygen atoms as [LaO9]15- polyhedron without any contact with X- anions. Single-crystal Raman measurements were performed for La5Cl3[SbO3]4 and LaSb12O19I4, and La5Cl3[SbO3]4 was structurally compared with the isostoichiometric, but not isotypic La5F3[SbO3]4.
Open Access
The true nature of SmSb2O4Cl : syntheses and crystal structures of Sm2[Sb4O8]Cl2 and Eu2[Sb4O8]Cl2
(2022) Locke, Ralf J. C.; Schleid, Thomas
The two lanthanoid oxidoantimonate(III) chlorides SmSb2O4Cl and EuSb2O4Cl are accessible from solid‐state reactions of Sb2O3 with Ln2O3 and LnCl3 (Ln=Sm and Eu) at 750 °C for two days. They crystallize in the centrosymmetric tetragonal space group P4/ncc with the lattice parameters a=787.13(4) pm, c=1765.24(12) pm for SmSb2O4Cl and a=783.56(4) pm, c=1764.05(12) pm for EuSb2O4Cl with Z=8. Both can also be described with the crystal‐chemical formula Ln2[Sb4O8]Cl2 for Z=4, since they comprise isolated [Sb4O8]4- rings. This structural motif has some very close similarities to the known series of non‐centrosymmetric LnSb2O4Cl representatives (Ln=Gd-Lu), crystallizing in the tetragonal space group P4212. All lanthanoid(III) cations have eight oxygen atoms as nearest neighbors arranged as square prisms [LnO8]13-, which are connected to layers by four parallel edges according to ∞2{[LnO8/2e]5-} with fluorite‐like topology. The Sb3+ cations together with three oxygen atoms each and their lone‐pair of electrons form ψ1‐tetrahedra [SbO3]3-. Four of these [SbO3]3- entities join to ∞0Sb4O84- rings with four bridging and four terminal oxygen atoms. Both centrosymmetric representatives, in contrast to the series of non‐centrosymmetric ones, have a doubled lattice parameter c and several more symmetry elements, which will be discussed in detail.
Open Access
Two new members of the lanthanoid bismuth oxide oxidosilicates LnBiO[SiO4] with Ln=La and Gd
(2023) Locke, Ralf J. C.; Haag, Tanja; Hartenbach, Ingo; Kurz, Melanie V.; Blaschkowski, Björn; Schleid, Thomas
The isostructural lanthanoid bismuth oxide oxidosilicates with the formula LnBiO[SiO4] (Ln=La and Gd) crystallize in the triclinic space group urn:x-wiley:00442313:media:zaac202300126:zaac202300126-math-0001 with the lattice parameters a=571.04(3) pm, b=681.13(4) pm, c=697.98(4) pm and α=105.805(2)°, β=110.456(2)°, γ=99.871(2)°, Vuc=0.23380(2) nm3 for Ln=La and a=554.12(3) pm, b=670.68(4) pm, c=689.57(4) pm and α=104.619(2)°, β=110.793(2)°, γ=99.560(2)°, Vuc=0.22237(2) nm3 for Ln=Gd with Z=2 for both. Colorless single crystals were serendipitously obtained from the reaction of bismuth sesquioxide, bismuth trifluoride and the lanthanoid sesquioxides at 850 °C in unprotected torch-sealed silica ampoules as SiO2 source. Their crystal structure features Ln3+ cations surrounded by eight oxygen atoms as distorted square antiprisms [LnO8]13−, which are linked via edges with three further polyhedra of this kind to form layers urn:x wiley:00442313:media:zaac202300126:zaac202300126-math-0002 {[LnOurn:x-wiley:00442313:media:zaac202300126:zaac202300126-math-0003 Ourn:x-wiley:00442313:media:zaac202300126:zaac202300126-math-0004 ]7-} within the (010) plane. The oxygen environment of the Bi3+ cations has to be described as ψ1-octahedral (square pyramids [BiO5]7−) with five oxide ligands and the stereochemically active lone pair. Two of them are edge-linked to form ψ1-bioctahedra [Bi2O8]10−. Four out of five oxygen atoms belong to discrete [SiO4]4− tetrahedra, which separate urn:x-wiley:00442313:media:zaac202300126:zaac202300126-math-0005 {[OLnurn:x wiley:00442313:media:zaac202300126:zaac202300126-math-0006 Biurn:x wiley:00442313:media:zaac202300126:zaac202300126-math-0007 ]4+} chains of trans-edge connected [OLn2Bi4]10+ tetrahedral, centered by the fifth oxygen atom propagating along [100] for charge compensation. Furthermore, the magnetic properties of GdBiO[SiO4] were investigated, showing Curie-Weiss behavior without any magnetic ordering phenomena down to lowest temperatures.
Open Access
Y5F3[AsO3]4 and Y5Cl3[AsO3]4 : two non-isostructural yttrium halide oxoarsenates(III) and their potential as hosts for luminescent Eu3+- and Tb3+-doping
(2025) Locke, Ralf J. C.; Mikuta, Martina; Ledderboge, Florian; Zimmer, Frank C.; Höppe, Henning A.; Schleid, Thomas
Y5F3[AsO3]4 crystallizes needle-shaped in the tetragonal space group P4/ncc with the lattice parameters a = 1143.80(8) pm, c = 1078.41(7) pm and c/a = 0.9428 for Z = 4. The yttrium-fluoride substructure linked via secondary contacts forms a three-dimensional network 3∞{[Y5F3]12+} and the remaining part consists of ψ1-tetrahedral [AsO3]3- units, which leave lone-pair channels along [001]. In contrast, platelet-shaped Y5Cl3[AsO3]4 crystals adopt the monoclinic space group C2/c with the lattice parameters a = 1860.56(9) pm, b = 536.27(3) pm, c = 1639.04(8) pm and β = 105.739(3)° for Z = 4. Condensation of [(Y1,2)O8]13- polyhedra via four common edges each leads to fluorite-like 2∞ {[(Y1,2)Oe8/2]5-} layers spreading out parallel to the (100) plane. Their three-dimensional linkage occurs via the (Y3)3+ cations with their Cl- ligands on the one hand and the As3+ cations with their lone-pairs of electrons on the other, which also form within [AsO3]3- anions lone-pair channels along [010]. Both colorless compounds can be obtained by solid-state reactions from corresponding mixtures of the binaries (Y2O3, As2O3 and YX3 with X = F and Cl) at elevated temperatures of 825 °C, most advantageously under halide-flux assistance (CsBr for Y5F3[AsO3]4 and ZnCl2 for Y5Cl3[AsO3]4). By replacing a few percent of YX3 with EuX3 or TbX3, Eu3+- or Tb3+-doped samples are accessible, which show red or green luminescence upon excitation with ultraviolet radiation.