Layered perovskite-related ruthenium oxychlorides: crystal structure of two new compounds Ba5Ru2Cl2O9 and Ba6Ru3Cl2O12

Single crystals of the title compounds were prepared using a BaCl₂ flux and investigated by X-ray diffraction methods using MoKα radiation and a charge coupled device (CCD) detector. The crystal structures of these two new compounds were solved and refined in the hexagonal symmetry with space group P6₃/mmc, a=5.851(1) Å, c=25.009(5) Å, ρ_cal=4.94 g cm⁻³, Z=2 to a final R₁=0.069 for 20 parameters with 312 reflections for Ba₅Ru₂Cl₂O₉ and space group , a=5.815(1) Å, c=14.915(3) Å, ρ_cal=5.28 g cm⁻³, Z=1 to a final R₁=0.039 for 24 parameters with 300 reflections for Ba₆Ru₃Cl₂O₁₂. The structure of Ba₅Ru₂Cl₂O₉ is formed by the periodic stacking along [001] of three hexagonal close-packed BaO₃ layers separated by a double layer of composition Ba₂Cl₂. The BaO₃ stacking creates binuclear face-sharing octahedra units Ru₂O₉ containing Ru(V). The structure of Ba₆Ru₃Cl₂O₁₂ is built up by the periodic stacking along [001] of four hexagonal close-packed BaO₃ layers separated by a double layer of composition Ba₂Cl₂. The ruthenium ions with a mean oxidation degree +4.67 occupy the octahedral interstices formed by the four layers hexagonal perovskite slab and then constitute isolated trinuclear Ru₃O₁₂ units. These two new oxychlorides belong to the family of compounds formulated as [Ba₂Cl₂][Ba_n+1Ru_nO_3n+3], where n represents the thickness of the octahedral string in hexagonal perovskite slabs.     

Synthesis, structure, and magnetic properties of Ba2Cu2US5

The alkaline-earth uranium chalcogenide Ba₂Cu₂US₅ was obtained in a two-step reaction from BaS, Cu₂S, and US₂. Ba₂Cu₂US₅ crystallizes in a new structure type in space group C2/m of the monoclinic system with two formula units in a cell of dimensions a=13.606(3) Å, b=4.0825(8) Å, c=9.3217(19) Å, and β=116.32(3)° (153 K). The structure consists of layers separated by Ba atoms in bicapped trigonal-prismatic coordination. The two-dimensional layer is built from US₆ octahedra and CuS₄ tetrahedra. The connectivity of the MS_n polyhedra within the layer in the [001] direction is oct tet tet oct tet tet. A μ_eff value of 2.69(2) μ_B/U was obtained from the magnetic susceptibility data. No magnetic transition was observed for Ba₂Cu₂US₅ down to 2 K.     

Layered ruthenium hexagonal perovskites: The new series [Ba2Br2−2x(CO3)x][Ban+1RunO3n+3] with n=2, 3, 4, 5

Single crystals of the title compounds were prepared by solid state reactions from barium carbonate and ruthenium metal using a BaBr₂ flux and investigated by X-ray diffraction method using Mo(Kα) radiation and a Charge Coupled Device (CCD) detector. A structural model for the term n=2, Ba₅Ru₂Br₂O₉ (1) was established in the hexagonal symmetry, space group P6₃/mmc, a=5.8344(2) Å, c=25.637(2) Å, Z=2. Combined refinement and maximum-entropy method (MEM) unambiguously show the presence of CO₃²⁻ ions in the three other compounds (2, 3, 4). Their crystal structures were solved and refined in the trigonal symmetry, space group , a=5.8381(1) Å, c=15.3083(6) Å for the term n=3, Ba₆Ru₃Br_1.54(CO₃)_0.23O₁₂ (2), and space group , a=5.7992(1) Å, c=52.866(2) Å and a=5.7900(1) Å, c=59.819(2) Å for the terms n=4, Ba₇Ru₄Br_1.46(CO₃)_0.27O₁₅ (3), and n=5, Ba₈Ru₅Br_1.64(CO₃)_0.18O₁₈ (4), respectively. The structures are formed by the periodic stacking along [0 0 1] of (n+1) hexagonal close-packed [BaO₃] layers separated by a double layer of composition [Ba₂Br_2−2x(CO₃)_x]. The ruthenium atoms occupy the n octahedral interstices created in the hexagonal perovskite slabs and constitute isolated dimers Ru₂O₉ of face-shared octahedra (FSO) in 1 and isolated trimers Ru₃O₁₂ of FSO in 2. In 3 and 4, the Ru₂O₉ units are connected by corners either directly (3) or through a slab of isolated RuO₆ octahedra (4) to form a bidimensional arrangement of RuO₆ octahedra. These four oxybromocarbonates belong to the family of compounds formulated [Ba₂Br_2−2x(CO₃)_x][Ba_n+1Ru_nO_3n+3] where n represents the thickness of the octahedral string in hexagonal perovskite slabs. These compounds are compared to the oxychloride series.     

New Ba5M5−xPtxClO13 (M=Fe, Co) oxychlorides with layered perovskite-related structure

Crystals of Ba₅Fe_5−xPt_xClO₁₃ and Ba₅Co_5−yPt_yClO₁₃ were prepared for x=1.31, 1.51, 1.57, 1.59 and y=0, 0.97 and 1.08 in a BaCl₂ flux and investigated by X-ray diffraction methods. These compounds adopt a 10H perovskite structure built from the stacking of BaO₃ and BaOCl layers in the sequence (BaO₃)₄(BaOCl) with space group P6₃/mmc. The cation sites within the trimeric unit of face-sharing octahedra are occupied by Co or Fe and Pt ions, while the tetrahedral sites formed between BaO₃ and BaOCl layers are only occupied by Fe or Co. Moreover, oxygen stoichiometry indicates an average oxidation state for Co and Fe higher than +III, indicating the stabilization of Co⁴⁺ and Fe⁴⁺.     

Crystal growth of a novel oxygen-deficient layered perovskite: Ba7Li3Ru4O20

Single crystals of both Ba₇Li₃Ru₄O₂₀ and Ba₄NaRu₃O₁₂ were grown from reactive molten hydroxide fluxes. Ba₇Li₃Ru₄O₂₀ is a 7L-layer perovskite-related phase resulting from the stacking of six [AO₃] layers and one oxygen deficient [AO₂] layer, thereby creating LiO₄ tetrahedra in addition to the LiO₆ octahedra and face-sharing Ru₂O₉ bi-octahedra formed from the [AO₃] layers. The compound crystallizes in the space group with a=5.7927(1) Å and c=50.336(2) Å, Z=3. Ba₄NaRu₃O₁₂ crystallizes in the space group P6₃mc with lattice parameters of a=5.8014(2) Å and c=19.2050(9) Å, Z=2. Ba₄NaRu₃O₁₂ is identical to a previously reported neutron refinement structure. The magnetic properties of Ba₇Li₃Ru₄O₂₀ are also reported.     

Synthesis, crystal structure and optical properties of BiMgVO5

The new vanadate BiMgVO₅ has been prepared and its structure has been determined by single crystal X-ray diffraction: space group P2₁/n, , , , β=107.38(5)°, wR₂=0.0447, R=0.0255. The structure consists of [Mg₂O₁₀] and [Bi₂O₁₀] dimers sharing their corners with [VO₄] tetrahedra. The ranges of bond lengths are 2.129-2.814 Å for Bi-O; 2.035-2.167 Å for Mg-O and 1.684-1.745 Å for V-O. V-O bond lengths determined from Raman band wavenumbers are between 1.679 and 1.747 Å. An emission band overlapping the entire visible region with a maximum around 650 nm is observed.     

The local structure and composition of Ba4Nb2O9-based oxycarbonates

X-ray powder-diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), electron diffraction (ED), infrared spectroscopy (IR), thermogravimetry (TG) and mass spectroscopy (MS) were performed to investigate the composition and the crystal structure of tetra-barium di-niobate (V) Ba₄Nb₂O₉. The TG, MS and IR studies revealed that the compound is a hydrated oxycarbonate. Assuming that the carbonate stoichiometrically replaces oxygen, the composition of the low-temperature α-modification, obtained by slow cooling from 1100 °C, corresponds to Ba₄Nb₂O_8.8(CO₃)_0.2·0.1H₂O, while the quenched high-temperature γ-modification has the Ba₄Nb₂O_8.42(CO₃)_0.58·0.38H₂O composition. The α-phase has a composite incommensurately modulated structure consisting of two mutually interacting [Ba]_∞ and the [(Nb,□)O₃]_∞ subsystems. The composite modulated crystal structure of the α-phase can be described with the lattice parameters a=10.2688(1) Å, c=2.82426(8) Å, q=0.66774(2)c* and a superspace group Rm(00γ)0s. The HRTEM analysis demonstrates the nanoscale twinning of the trigonal domains parallel to the {1 0 0} crystallographic planes. The twinning introduces a one-dimensional disorder into the [(Nb,□)O₃]_∞ subsystem, which results in an average P2c crystal structure of the α-phase. Possible places for the carbonate group in the structure are discussed using a comparison with other hexagonal perovskite-based oxycarbonates.     

Synthesis, crystal structure, and magnetic properties of new layered hexagonal perovskite Ba8Ta4Ru8/3Co2/3O24

A new hexagonal perovskite-type oxide Ba₈Ta₄Ru_8/3Co_2/3O₂₄ was synthesized by the solid-state method at 1573 K and characterized by electron diffraction (ED), time-of-flight (TOF) neutron powder diffraction, and magnetic susceptibility. Structure parameters of Ba₈Ta₄Ru_8/3Co_2/3O₂₄ were refined by the Rietveld method from the TOF neutron powder diffraction data on the basis of space group P6₃/mcm and lattice parameters a=10.0075(1) Å and c=18.9248(2) Å as obtained from the ED data (Z=3). The crystal structure of Ba₈Ta₄Ru_8/3Co_2/3O₂₄ consists of 8-layered (cchc)₂ close-packed stacking of BaO₃ layers along the c-axis. Corner-shared octahedra are filled by Ta only and face-shared octahedra are statistically occupied by Ru, Co, and vacancies. Similar compounds Ba₈Ta₄Ru_8/3M_2/3O₂₄ with M=Ni and Zn were also prepared. Magnetic susceptibility measurements showed no magnetic ordering down to 5 K.     

Synthesis, crystal structure and characterization of new 12H hexagonal perovskite-related oxides Ba6M2Na2X2O17 (M=Ru, Nb, Ta, Sb; X=V, Cr, Mn, P, As)

The new Ba₆Ru₂Na₂X₂O₁₇ (X=V, Mn) compounds have been prepared by electrosynthesis in molten NaOH and their crystal structures have been refined from single crystals X-ray diffraction, space group P6₃/mmc, Z=2, for X=V: , , R₁=4.76%, for X=Mn : , , R₁=3.48%. The crystal structure is a 12H-type perovskite with a (c′cchcc)₂ stacking sequence of [BaO₃]_c, [BaO₃]_h and [BaO₂]_c′ layers. The tridimensional edifice is formed by blocks of Ru₂O₉ dimers that share corners with NaO₆ octahedra. These blocks sandwich double sheets of X⁵⁺O₄ tetrahedra. Several isotypic Ba₆M⁵⁺₂Na₂X⁵⁺₂O₁₇ materials (X=V, Cr, Mn, P, As) and (M=Ru, Nb, Ta, Sb) have been prepared by solid state reaction and characterized by Rietveld analysis. The magnetic and electric properties have been investigated and show besides the Ru⁵⁺₂O₉ typical intradimer antiferromagnetic couplings, discrepancies of both χ and ρ versus T at 50 and 100 K for Ba₆Ru₂Na₂X₂O₁₇ (X=V, As). In this work, a review of the identified Ru-hexagonal perovskite materials is also reported in order to overview the wide variety of possibilities in the field of new compounds synthesis.     

Synthesis, crystal structure, and magnetic properties of the manganate La2Ca2MnO6(O2) related to the hexagonal perovskite-type structure

The compound La₂Ca₂MnO₆(O₂) has been synthesized from La₂Ca₂MnO₇ heated at 1123 K under high pressure (4 GPa) with KClO₃ as oxygen source. The crystal structure has been refined from X-ray powder data in the space group. The unit-cell parameters are a=5.6335(2) Å and c=17.4879(8) Å. Perpendicular to the c-axis, the structure is built up by the periodic stacking of two close packed [LaO₃] layers separated by a layer of composition [Ca₂O₂] containing (O₂)²⁻ peroxide ions. This oxide belongs to the family of compounds formulated as [A′₂O_2−δ][A_nB_n−1O_3n] for n=2 and δ=0. It is the first member of the series where the thickness of the perovskite slab corresponds to one [BO₆] (B=Mn) octahedron. The structural relationships with La₂Ca₂MnO₇ are discussed and the magnetic properties show that in both phases manganese is tetravalent.     

Sr10[(PO4)5.5(BO4)0.5](BO2): Growth and crystal structure of a strontium phosphate orthoborate metaborate closely related to the apatite-type crystal structure

Single crystals of the strontium phosphate orthoborate metaborate, Sr₁₀[(PO₄)_5.5(BO₄)_0.5](BO₂), were grown from the melt and investigated by X-ray diffraction (space group , No. 147; a=9.7973(8) Å, c=7.3056(8) Å, V=607.29(10) Å³, Z=1). The crystal structure is closely related to apatite and contains linear metaborate groups, [BO₂]⁻ (point group D_∞h, B-O=1.284(11) Å) taking positions within the channels running along the three-fold inversion axis. Strontium sites are found to be fully occupied while [PO₄]³⁻ tetrahedra are partially replaced by [BO₄]⁵⁻ groups.     

Synthesis, structure, and characterization of a new one-dimensional tellurite phosphate, Ba2TeO(PO4)2

A new one-dimensional tellurite phosphate, Ba₂TeO(PO₄)₂ has been synthesized by standard solid-state reaction techniques using BaCO₃, TeO₂, and (NH₄)H₂PO₄ as reagents. The structure of Ba₂TeO(PO₄)₂ was determined by single-crystal X-ray diffraction. Ba₂TeO(PO₄)₂ crystallizes in the triclinic space group P-1 (No. 2), with , , , α=76.843(4)°, β=79.933(4)°, γ=75.688(4)°, , and Z=2. Ba₂TeO(PO₄)₂ has a novel one-dimensional chain structure that is composed of PO₄ tetrahedra and TeO₅ polyhedra. Te⁴⁺ cations are in asymmetric coordination environments attributable to their lone pairs. The lone pairs on the Te⁴⁺ cations point in the [100] and [−100] direction and interact with the Ba²⁺ cations. Infrared, Raman, and UV-Vis diffuse reflectance spectroscopy, thermogravimetric analysis, and dipole moment calculations are also presented.     

[C6H21N4][Sb9S14O]: Solvothermal synthesis, crystal structure and characterization of the first non-centrosymmetric open Sb-S-O framework containing the new [SbS2O] building unit

[C₆H₂₁N₄][Sb₉S₁₄O] represents the first known oxo-thioantimonate with an organic ion acting as structure director. The compound crystallizes in the non-centrosymmetric space group Cmc2₁ with a=29.679(2), b=9.9798(6), , , Z=4. The structure contains the hitherto unknown [SbS₂O] unit as a structural motif. The [SbS₃] trigonal pyramids and [SbS₂O] units are joined to form a 10-membered ring with large pores having a diameter of 7.7 Å×8.3 Å. The organic template molecule acts like a tetra-dentate ligand around the O atom of the [SbS₂O] group. Depending on the value chosen for the Sb-S bond lengths, the material contains a 1-, 2- or 3-dimensional anion. The optical band gap of 2.03 eV demonstrates that the material is an optical semi-conductor. Upon heating, the compound decomposes in two steps yielding finally a mixture of Sb and Sb₂S₃. The ¹²¹Sb Mössbauer spectrum shows a relative large line width in accordance with the superposition of the five signals.     

Structural and magnetic properties of Ba3La3Mn2W3O18

A quaternary phase, Ba₃La₃Mn₂W₃O₁₈, was synthesized in reduced atmosphere (5% H₂/Ar) at 1200 °C and characterized by using powder X-ray diffraction, electron diffraction and high resolution TEM. Ba₃La₃Mn₂W₃O₁₈ crystallizes in rhombohedral space group with the cell parameters, and , and can be attributed to the n=6 member in the B-site deficient perovskite family, A_nB_n−1O_3n. The structure can be described as close-packed [La/BaO₃] arrays in the sequence of (hcccch)₃, wherein the B-site cations, W and Mn, occupy five octahedral layers in every six octahedral layers, which leave a vacant octahedral layers separating the 5-layer perovskite blocks. The B-cation layers in the perovskite block alternate along the c-axis in a sequence of W⁶⁺-Mn²⁺-W⁵⁺-Mn²⁺-W⁶⁺. The bond valence calculation and optical reflection spectrum confirm the presence of W⁵⁺. This compound behaves paramagnetically in wide temperature range and weak antiferromagnetic interaction only occurs at low temperatures.     

Synthesis and single crystal structures of ternary phosphides Li4SrP2 and AAeP (A=Li, Na; Ae=Sr, Ba)

Two new (NaSrP, Li₄SrP₂) and two known (LiSrP, LiBaP) ternary phosphides have been synthesized and characterized using single crystal X-ray diffraction studies. NaSrP crystallizes in the non-centrosymmetric hexagonal space group (#189, a=7.6357(3) Å, c=4.4698(3) Å, V=225.69(2) Å³, Z=3, and R/wR=0.0173/0.0268). NaSrP adopts an ordered Fe₂P structure type. PSr₆ trigonal prisms share trigonal (pinacoid) faces to form 1D chains. Those chains define large channels along the [001] direction through edge-sharing. The channels are filled by chains of PNa₆ face-sharing trigonal prisms. Li₄SrP₂ crystallizes in the rhombohedral space group (#166, a=4.2813(2) Å, c=23.437(2) Å, V=372.04(4) Å³, Z=3, and R/wR=0.0142/0.0222). In contrast to previous reports, LiSrP and LiBaP crystallize in the centrosymmetric hexagonal space group P6₃/mmc (#194, a=4.3674(3) Å, c=7.9802(11) Å, V=131.82(2) Å³, Z=2, and R/wR=0.0099/0.0217 for LiSrP; a=4.5003(2) Å, c=8.6049(7) Å, V=150.92(2) Å³, Z=2, and R/wR=0.0098/0.0210 for LiBaP). Li₄SrP₂, LiSrP, and LiBaP can be described as Li₃P derivatives. Li atoms and P atoms make a graphite-like hexagonal layer, . In LiSrP and LiBaP, Sr or Ba atoms reside between layers to substitute for two Li atoms of Li₃P, while in Li₄SrP₂, Sr substitutes only between every other layer.     

Syntheses, crystal structures and spectroscopic properties of Ag2Nb[P2S6][S2] and KAg2[PS4]

Ag₂Nb[P₂S₆][S₂] (1) was obtained from the direct solid state reaction of Ag, Nb, P₂S₅ and S at 500 °C. KAg₂[PS₄] (2) was prepared from the reaction of K₂S₃, Ag, Nd, P₂S₅ and extra S powder at 700 °C. Compound 1 crystallizes in the orthorhombic space group Pnma with a=12.2188(11), b=26.3725(16), c=6.7517(4) Å, V=2175.7(3) Å³, Z=8. Compound 2 crystallizes in the non-centrosymmetric tetragonal space group with lattice parameters a=6.6471(7), c=8.1693(11) Å, V=360.95(7) Å³, Z=2. The structure of Ag₂Nb[P₂S₆][S₂] (1) consists of [Nb₂S₁₂], [P₂S₆] and new found puckered [Ag₂S₄] chains which are along [001] direction. The Nb atoms are located at the center of distorted bicapped trigonal prisms. Two prisms share square face of two [S₂²⁻] to form one [Nb₂S₁₂] unit, in which Nb-Nb bond is formed. The [Nb₂S₁₂] units share all S²⁻ corners with ethane-like [P₂S₆] units to form 14-membered rings. The novel puckered [Ag₂S₄] chains are composed of distorted [AgS₄] tetrahedra and [AgS₃] triangles that share corners with each other. These chains are connected with [P₂S₆] units and [Nb₂S₁₂] units to form three-dimensional frame work. The structural skeleton of 2 is built up from [AgS₄] and [PS₄] tetrahedra linked by corner-sharing. The three-dimensional anionic framework contains orthogonal, intersecting tunnels directed along [100] and [010]. This compound possesses a compressed chalcopyrite-like structure. The structure is compressed along [001] and results from eight coordination sphere for K⁺. Both compounds are characterized with UV/vis diffuse reflectance spectroscopy and compound 1 with IR and Raman spectra.     

Crystal structure and magnetic properties of Cu3(TeO3)2Br2—a layered compound with a new Cu(II) coordination polyhedron

The new compound Cu₃(TeO₃)₂Br₂ crystallizes in the monoclinic spacegroup C2/m. The unit cell parameters are a=9.3186(18)Å, b=6.2781(9)Å, c=8.1999(16)Å, β=107.39(2)°, Z=2. The structure is solved from single crystal data, R₁=0.021. The new compound shows a layered structure where only weak van der Waals interactions connect the layers. There are two crystallographically different Cu(II) atoms; one having a square planar [CuO₄] coordination and one showing an unusual [CuO₄Br] trigonal bi-pyramidal coordination, the Br-ion is located in the equatorial plane. The Te(IV) atom has a tetrahedral [TeO₃E] coordination where E is the 5s² lone-pair. Within the layers the Cu-polyhedra are connected by corner- and edge sharing to form chains. The chains are separated by the Te atoms. The magnetic properties are dominated by long range magnetic ordering at . Evidence for a coexistence of ferromagnetic and antiferromagnetic interactions exists.