Neutron powder diffraction study of tetragonal Li7La3Hf2O12 with the garnet-related type structure

We have successfully synthesized a polycrystalline sample of tetragonal garnet-related Li-ion conductor Li₇La₃Hf₂O₁₂ by solid state reaction. The crystal structure is analyzed by the Rietveld method using neutron powder diffraction data. The structure analysis identifies that tetragonal Li₇La₃Hf₂O₁₂ has the garnet-related type structure with a space group of I4₁/acd (no. 142). The lattice constants are a=13.106(2) Å and c=12.630(2) Å with a cell ratio of c/a=0.9637. The crystal structure of tetragonal Li₇La₃Hf₂O₁₂ has the garnet-type framework structure composed of dodecahedral La(1)O₈, La(2)O₈ and octahedral HfO₆. Li atoms occupy three types of crystallographic site in the interstices of this framework structure, where Li(1) atom is located at the tetrahedral 8a site, and Li(2) and Li(3) atoms are located at the distorted octahedral 16f and 32g sites, respectively. These Li sites are filled with the Li atom. The present tetragonal Li₇La₃Hf₂O₁₂ sample exhibits bulk Li-ion conductivity of σ_b=9.85×10⁻⁷ S cm⁻¹ and grain-boundary Li-ion conductivity of σ_gb=4.45×10⁻⁷ S cm⁻¹ at 300 K. The activation energy is estimated to be E_a=0.53 eV in the temperature range of 300-580 K.     

Structure determination from powder diffraction data and thermal behaviour of layered lead nitrate oxalate hydrate, Pb2(NO3)2(C2O4).2H2O

The mixed lead nitrate oxalate, Pb₂(NO₃)₂(C₂O₄).2H₂O, has been obtained in a polycrystalline form in the course of a study on precursors of nanocrystalline PZT-type oxides. Its crystal structure has been solved from powder diffraction data collected using a monochromatic radiation from a conventional X-ray source. The symmetry is monoclinic, space group P2₁/c (No. 14), the cell dimensions are a=10.623(2) Å, b=7.9559(9) Å, c=6.1932(5) Å, β=104.49(1)° and Z=4. The structure consists of a stacking of complex double sheets parallel to (1 0 0), forming layers held together by hydrogen bonds. The sheets result from the condensation of PbO₁₀ polyhedra, in which the oxalate and nitrate groups, as well as water molecules, play a major role. The structure is discussed in terms of Pb---O distances, polyhedra shape and lead coordination, with emphasis on the dimensional polymerisation role of water molecules. The thermal behaviour of this layered compound is carefully described from temperature-dependent powder diffraction and thermogravimetric measurements. The enthalpy, Δ_rH=232(3) kJ mol⁻¹, and entropy, Δ_rS=532(8) J K⁻¹ mol⁻¹, of the dehydration reaction have been determined. The high value of Δ_rH demonstrates that the water molecules are strongly bonded in the structure. The complex decomposition proceeds through the crystallisation and decomposition of Pb(NO₃)₂(C₂O₄) into Pb(NO₃)₂ and PbC₂O₄, and, finally, various lead oxides.     

Structure, crystal chemistry and thermal evolution of the δ-Bi2O3-related phase Bi9ReO17

The thermal evolution and structural properties of fluorite-related δ-Bi₂O₃-type Bi₉ReO₁₇ were studied with variable temperature neutron powder diffraction, synchrotron X-ray powder diffraction and electron diffraction. The thermodynamically stable room-temperature crystal structure is monoclinic P2₁/c, a=9.89917(5), b=19.70356(10), c=11.61597(6) Å, β=125.302(2)° (R_p=3.51%, wR_p=3.60%) and features clusters of ReO₄ tetrahedra embedded in a distorted Bi–O fluorite-like network. This phase is stable up to 725 °C whereupon it transforms to a disordered δ-Bi₂O₃-like phase, which was modeled with δ-Bi₂O₃ in cubic Fm3¯m with a=5.7809(1) Å (R_p=2.49%, wR_p=2.44%) at 750 °C. Quenching from above 725 °C leads to a different phase, the structure of which has not been solved but appears on the basis of spectroscopic evidence to contain both ReO₄ tetrahedra and ReO₆ octahedra.     

Conductivity studies of dense yttrium-doped BaZrO3 sintered at 1325 °C

High-temperature proton conductors have wide applications in the areas of fuel cells, electrolysis and hydrogen separation. Barium zirconate-based materials are of interest due to their good stability and high protonic conductivity. The reported conductivity of these ceramic materials is generally less than 10⁻² S/cm, even at high temperatures. This is not high enough for an electrolyte-supported device to achieve an ASR of less than 0.2 Ω cm² therefore thin film electrolytes are required for successful application. As BaZrO₃-based materials have to be sintered at temperatures as high as 1700 °C, this makes it difficult to find a suitable supporting electrode which will not undergo significant chemical reaction with the BaZrO₃-based electrolyte during fabrication of the required electrode supported electrolyte. In this paper, proton-conducting BaZr_0.8Y_0.2O_2.9 was successfully sintered at 1325 °C with a relative density of 96% via addition of 1 wt% ZnO. Fabrication of electrochemical cells using proton-conducting BaZr_0.8Y_0.2O_2.9 as the electrolyte thus becomes possible. The formula of the 1 wt% ZnO added sample is Ba_0.97Zr_0.77Y_0.19Zn_0.04O_3−δ which exhibits a tetragonal structure with space group P4/mbm (127); a=5.9787(1) Å, c=4.2345(1) Å, V=151.36(1) Å³. It was found that a solid solution was formed for a limited range of Zn doping. Conductivity has been studied as a function of atmosphere (air, dry and wet 5% H₂/Ar) with the changes in bulk and grain boundary on changing atmosphere being monitored as a function of time. The total conductivity of Ba_0.97Zr_0.77Y_0.19Zn_0.04O_3–δ is 1.0×10⁻³ S/cm above 600 °C therefore it may be used as a proton-conducting thin film electrolyte for efficient electrochemical devices at such temperatures. The grain boundary resistance is insignificant at high temperature for the well-sintered sample.     

Synthesis and crystal structure analysis of Sr8Cu3In4N5 and Sr0.53Ba0.47CuN

Single crystals of new quaternary compounds Sr₈Cu₃In₄N₅ and Sr_0.53Ba_0.47CuN were prepared, respectively, from a Sr–Cu–In–Na melt under 7 MPa of N₂ and from a Sr–Ba–Cu–In–Na melt under 0.5 MPa of N₂ by slow cooling from 1023 to 823 K. The crystal structures were determined by single-crystal X-ray diffraction. Sr₈Cu₃In₄N₅ has an orthorhombic structure (space group, Immm, Z=2, a=3.8161(5) Å, b=12.437(2) Å, c=18.902(2) Å), and is isostructural with Ba₈Cu₃In₄N₅. It contains nitridocuprates of isolated units ⁰[CuN₂] and one-dimensional linear chains _∝¹[CuN_2/2] and one-dimensional indium clusters _∝¹[In₂In_2/2]. Sr_0.53Ba_0.47CuN crystallizes in an orthorhombic cell, space group Pbcm, Z=4, a=5.4763(7) Å, b=9.2274(12) Å, c=9.0772(12) Å. The structure contains infinite zig-zag chains _∝¹[CuN_2/2] which kink at every second nitrogen atom.     

Li3−xTi2(PO4)3 (0 ≤ x ≤ 1): A new mixed valent titanium(III/IV) phosphate with a NASICON-type structure

A new NASICON-related structure of lithium titanium phosphate Li_2.72Ti₂(PO₄)₃ has been determined. This compound crystallizes in an orthorhombic system, Pbcn, with a = 12.064 (3) Å, b = 8.663 (3) Å, c = 8.711 (4) Å, V = 910.4 (8) ų, and Z = 4. The single crystal structure of this novel mixed valent titanium(III/IV) phosphate reveals one titanium atom per asymmetric unit. Two lithium sites are characterized by a pair of distorted polyhedra, Li(1)O₄ and Li(2)O₅, which share a common edge resulting in a short Li(1) … Li(2) distance, i.e., 2.29 (5) Å. Magnetic susceptibility and microprobe analysis confirmed the structural composition. The room temperature ionic conductivity is comparable with that of the known Li_1+xTi^IV_2−xIn^III_x(PO₄)₃, which suggests possible fast ionic conductivity.     

Syntheses, crystal structures and spectroscopic properties of KEu[AsS4], K3Dy[AsS4]2 and Rb4Nd0.67[AsS4]2

Three rare earth compounds, KEu[AsS₄] (1), K₃Dy[AsS₄]₂ (2), and Rb₄Nd_0.67[AsS₄]₂ (3) have been synthesized employing the molten flux method. The reactions of A₂S₃ (A = K, Rb), Ln (Ln = Eu, Dy, Nd), As₂S₃, S were accomplished at 600 °C for 96 h in evacuated fused silica ampoules. Crystal data for these compounds are: 1, monoclinic, space group P2₁/m (no. 11), a = 6.7276(7) Å, b = 6.7190(5) Å, c = 8.6947(9) Å, β = 107.287(12)°, Z = 2; 2, monoclinic, space group C2/c (no. 15), a = 10.3381(7) Å, b = 18.7439(12) Å, c = 8.8185(6) Å, β = 117.060(7)°, Z = 4; 3, orthorhombic, space group Ibam (no. 72), a = 18.7333(15) Å, b = 9.1461(5) Å, c = 10.2060(6) Å, Z = 4. 1 is a two-dimensional structure with ²_∞[Eu(AsS₄)]⁻ layers separated by potassium cations. Within each layer, distorted bicapped trigonal [EuS₈] prisms are linked through distorted [AsS₄]³⁻ tetrahedra. Each Eu²⁺ cation is coordinated by two [AsS₄]³⁻ units by edge-sharing and bonded to further two [AsS₄]³⁻ units by corner-sharing. Compound 2 contains a one-dimensional structure with ¹_∞[Dy(AsS₄)₂]³⁻ chains separated by potassium cations. Within each chain, distorted bicapped trigonal prisms of [DyS₈] are linked by slightly distorted [AsS₄]³⁻ tetrahedra. Each Dy³⁺ ion is surrounded by four [AsS₄]³⁻ moieties in an edge-sharing fashion. For compound 3 also a one-dimensional structure with ¹_∞[Nd₀.₆₇(AsS₄)₂]⁴⁻ chains is observed. But the Nd position is only partially occupied and overall every third Nd atom is missing along the chain. This cuts the infinite chains into short dimers containing two bridging [As₄]³⁻ units and four terminal [AsS₄]³⁻ groups. 1 is characterized with UV/vis diffuse reflectance spectroscopy, IR, and Raman spectra.     

Structure and properties of triclinic Ni0.85Mo6Te8

The structure of Ni_0.85Mo₆Te₈ was refined from single-crystal X-ray diffraction data at room temperature. It is triclinic, space group

Full-size image

; 1619 reflections, 75 refined parameters, R = 0.031. The Mo atoms form distorted octahedral clusters (2.69 Å ≤ d_intra[Mo---Mo] ≤ 2.81 Å; 3.58 Å < d_inter[Mo---Mo]). The Ni atoms are disordered (site occupancy: 0.423(7); d[Ni---Ni] = 2.586(6) Å), and interact strongly with one Mo₆ cluster (d[Ni---Mo] = 2.603(3) and 2.958(3) Å), and weakly with another (d[Ni---Mo] = 2.985(3) Å). The structure transforms at 1057(5) K into a rhombohedral modification (a_hex = 10.457(2) Å, c_hex = 11.866(3) Å at 1073 K). Measurements on powders suggest metallic conductivity (5.1 × 10⁻⁴ Ω-cm at 293 K) and weakly temperature-dependent paramagnetism (110 × 10⁻⁶ emu/g at 100 K).     

New mixed-halide, boron-centered zirconium cluster phases with different cation distributions within a cluster framework: syntheses and structures of A[(Zr6B)ClxI14−x] (A=Na or Cs, 0x4)

Two new mixed-halide zirconium cluster phases have been synthesized by solid-state reactions in sealed tantalum containers from the Zr(IV) halides, elemental Zr and B, and NaI or CsCl, respectively. Single-crystal X-ray data were used to determine the crystal structures of Na[(Zr₆B)Cl_3.9I_10.1], and Cs[(Zr₆B)Cl_2.2I_11.8]. Both phases crystallize in a stuffed version of the [Nb₆Cl₁₄] structure type, orthorhombic, space group Cmca (Na[(Zr₆B)Cl_3.87(5)I_10.13]: a=15.787(2) Å, b=14.109(2) Å, c=12.505(2) Å, Z=4, R1(F)=0.0322 and wR2(F²)=0.0842; Cs[(Zr₆B)Cl_2.16(5)I_11.84]: a=15.696(4) Å, b=14.156(4) Å, c=12.811(4) Å, Z=4, R1(F)=0.0404 and wR2(F²)=0.1031). This structure type is constructed of clusters which contain centered (Zr₆Z) octahedra of the type [(Zr₆Z)X₁₂ⁱX₆^a] with Z=B and X=Cl and/or I. In both structures, chlorine and iodine atoms are randomly (to X-rays) distributed on the inner non-cluster-interconnecting ligand positions, whereas those sites which bridge metal octahedra are solely occupied by iodine. The phase widths for both phases have been found to cover 0x4 for A^I[(Zr₆B)Cl_xI_14−x]. Whereas the sodium cations in Na[(Zr₆B)Cl_xI_14−x] occupy 25% of a site which is octahedrally surrounded by halogen atoms, the larger cations in the cesium-containing phase occupy a 12-coordinate site within the cluster network.     

X-ray diffraction and Mössbauer spectroscopy studies of LiFe0.5Ti1.5O4 – A new primitive cubic ordered spinel

LiFe_0.5Ti_1.5O₄ was synthesized by solid-state reaction carried out at 900 °C in flowing argon atmosphere, followed by rapid quenching of the reaction product to room temperature. The compound has been characterized by X-ray powder diffraction (XRD) and ⁵⁷Fe Mössbauer effect spectroscopy (MES). It crystallizes in the space group P4₃32, a = 8.4048(1) Å. Results from Rietveld structural refinement indicated 1:3 cation ordering on the octahedral sites: Li occupies the octahedral (4b) sites, Ti occupies the octahedral (12d) sites, while the tetrahedral (8c) sites have mixed (Fe/Li) occupancy. A small, about 5%, inversion of Fe on the (4b) sites has been detected. The MES data is consistent with cation distribution and oxidation state of Fe, determined from the structural data.The title compound is thermally unstable in air atmosphere. At 800 °C it transforms to a mixture of two Fe³⁺ containing phases – a face centred cubic spinel Li_(1+y)/2Fe_(5−3y)/2Ti_yO₄ and a Li_(z−1)/2Fe_(7−3z)/2Ti_zO₅ – pseudobrookite. The major product of thermal treatment at 1000 °C is a ramsdellite type lithium titanium iron(III) oxide, accompanied by traces of rutile and pseudobrookite.     

The Crystal Structures of the Strontium Gallates Sr10Ga6O19 and Sr3Ga2O6

The crystal structures of Sr₁₀Ga₆O₁₉ and Sr₃Ga₂O₆ have been characterized using X-ray diffraction techniques. In the case of Sr₁₀Ga₆O₁₉, the structure was determined from a single crystal diffraction data set collected at room conditions and refined to a final R index of 0.061 for 3471 observed reflections (I>2 σ(I)). The compound is monoclinic with space group C12/c1 (a=34.973(4) Å, b=7.934(1) Å, c=15.943(2) Å, β=103.55(1)°, V=4300.7(6) ų, Z=8, D_calc=4.94 g/cm³, μ(MoKα)=32.04 mm⁻¹) and can be classified as an oligogallate. It is the first example of an inorganic compound where six [TO₄]-tetrahedra of only one chemical species occupying the tetrahedral centres are linked via bridging oxygen atoms to form [T₆O₁₉] groups. The hexamers are not linear, but highly puckered. Eleven symmetrically different Sr cations located in planes parallel (100) crosslink between the oligo-groups. They are coordinated by six to eight oxygen ligands. The structure of Sr₃Ga₂O₆ has been refined from powder diffraction data using the Rietveld method (space group Pa , a=16.1049(1), V=4177.1(1) ų, Z=24, D_calc=4.75 g/cm³). The compound is isostructural with tricalcium aluminate and contains highly puckered, six-membered [Ga₆O₁₈]¹⁸⁻ rings. The rings are linked by strontium cations having six to nine nearest oxygen neighbors.     

Oxygen-deficient SrTiO3−x, X = 0.28, 0.17, and 0.08. Crystal growth, crystal structure, magnetic, and transport properties

The grossly nonstoichiometric perovskites SrTiO_3−x with x = 0.28, 0.17, and 0.08 were prepared from a reaction of Sr₂TiO₄, TiO, and TiO₂ at 1500°C. For x = 0.28 relatively large single crystals were obtained. Also for this sample the crystal symmetry was found to depend on the rate of cooling from the reaction temperature and the annealing conditions. Rapidly cooled samples are tetragonal a = 3.9177(3) Å, c = 3.8878(5) Å. Samples annealed in vacuum at temperatures of 1000 to 600°C are cubic a = 3.9075(3) Å with no change in cell volume. Single crystal data from a tetragonal sample indicate slight preferential occupancy of one oxygen position in P4/mmm. No evidence for any supercell due to defect ordering could be seen by TEM in either cubic or tetragonal samples. The x = 0.28 crystals show metallic resistivity, (300 K) = 6 × 10⁻⁴ ohm-cm and temperature-independent paramagnetism, χ_m = 118 × 10⁻⁶ cm³ mole⁻¹. Hall effect data from 300 to 4.2 K analyzed on a single carrier model give a temperature-independent n-type carrier density of 2.4 × 10²¹ cm⁻³. This is a factor of 3.9 less than that expected if the creation of each oxygen vacancy results in the production of two carriers in a single band. Hall data for x = 0.17 and 0.08 samples give similar results corresponding to densities of 2.1 and 1.4 × 10²¹ cm⁻³, respectively, in the same temperature range. These densities are 2.7 and 1.9 times less than the expected single-band value, respectively. Such results point to a two-band model with a large effective mass in one of the bands.     

Nb28Ni33.5Sb12.5, a New Representative of the X-phase

The first ternary compound in the Nb–Ni–Sb system, Nb₂₈Ni_33.5Sb_12.5, has been synthesized and its structure has been determined by single-crystal X-ray diffraction methods. Nb₂₈Ni_33.5(2)Sb_12.5(2) adopts the X-phase structure type (orthorhombic, space group Pnnm, Z=1, a=13.2334(5) Å, b=16.5065(7) Å, c=5.0337(2) Å), which belongs to the set of tetrahedrally close-packed (TCP) structures adopted by many intermetallic compounds. Typical of such TCP structures, the atoms reside in sites of high coordination number, with Ni and Sb in CN12 and Nb in CN14, -15, and -16 sites. The relative importance of various metal–metal bonding interactions is discussed on the basis of extended Hückel band structure calculations. Nb₂₈Ni_33.5Sb_12.5 displays metallic behavior with a room-temperature resistivity of 2.3×10⁻⁴ Ω cm.     

Structures and crystal chemistry of the double perovskites Ba2LnB′O6 (Ln=lanthanide and B′=Nb, Ta):: Part II—Temperature dependence of the structures of Ba2LnB′O6

The structures of eight members of the series of double perovskites of the type Ba₂LnB′O₆ (Ln=La³⁺-Sm³⁺ and Y³⁺ and B′=Nb⁵⁺ and Ta⁵⁺) were examined both above and below room temperature using synchrotron X-ray powder diffraction. The La³⁺ and Pr³⁺ containing compounds had an intermediate rhombohedral phase whereas the other tantalates and niobates studied have a tetragonal intermediate. This difference in symmetry appears to be a consequence of the larger size of the La³⁺ and Pr³⁺ cations compared to the other lanthanides. The temperature range over which the intermediate symmetry is stable is reduced in those compounds near the point where the preferred intermediate symmetry changes from tetragonal to rhombohedral. In such compounds the transition to the cubic phase involves higher order terms in the Landau expression. This suggests that in this region the stability of the two intermediate phases is similar.     

Synthesis, crystal structures, phase transition characterization and thermal decomposition of a new dabcodiium hexaaquairon(II) bis(sulfate): (C6H14N2)[Fe(H2O)6](SO4)2

The crystal structures of 1,4-diazabicyclo[2.2.2]octane (dabco)-templated iron sulfate, (C₆H₁₄N₂)[Fe(H₂O)₆](SO₄)₂, were determined at room temperature and at −173 °C from single-crystal X-ray diffraction. At 20 °C, it crystallises in the monoclinic symmetry, centrosymmetric space group P2₁/n, Z=2, a=7.964(5), b=9.100(5), c=12.065(5) Å, β=95.426(5)° and V=870.5(8) ų. The structure consists of [Fe(H₂O)₆]²⁺ and disordered (C₆H₁₄N₂)²⁺ cations and (SO₄)²⁻ anions connected together by an extensive three-dimensional H-bond network. The title compound undergoes a reversible phase transition of the first-order at −2.3 °C, characterized by DSC, dielectric measurement and optical observations, that suggests a relaxor–ferroelectric behavior. Below the transition temperature, the compound crystallizes in the monoclinic system, non-centrosymmetric space group Cc, with eight times the volume of the ambient phase: a=15.883(3), b=36.409(7), c=13.747(3) Å, β=120.2304(8)°, Z=16 and V=6868.7(2) ų. The organic moiety is then fully ordered within a supramolecular structure. Thermodiffractometry and thermogravimetric analyses indicate that its decomposition proceeds through three stages giving rise to the iron oxide.     

Original close-packed structure and magnetic properties of the Pb4Mn9O20 manganite

The crystal structure of the Pb₄Mn₉O₂₀ compound (previously known as “Pb_0.43MnO_2.18”) was solved from powder X-ray diffraction, electron diffraction, and high resolution electron microscopy data (S.G. Pnma, a=13.8888(2) Å, b=11.2665(2) Å, c=9.9867(1) Å, R_I=0.016, R_P=0.047). The structure is based on a 6H (cch)₂ close packing of pure oxygen “h”-type (O₁₆) layers alternating with mixed “c”-type (Pb₄O₁₂) layers. The Mn atoms occupy octahedral interstices formed by the oxygen atoms of the close-packed layers. The MnO₆ octahedra share edges within the layers, whereas the octahedra in neighboring layers are linked through corner sharing. The relationship with the closely related Pb₃Mn₇O₁₅ structure is discussed. Magnetization measurements reveal a peculiar magnetic behavior with a phase transition at 52 K, a small net magnetization below the transition temperature, and a tendency towards spin freezing.     

Synthesis, crystal structure, and preliminary study of luminescent properties of InTbGe2O7

A new indium terbium germanate InTbGe₂O₇, which is a member of the thortveitite family, was prepared as a polycrystalline powder material by high-temperature solid-state reaction. This new compound crystallizes in the monoclinic system, space group C2/c (No. 15), with unit cell parameters a=6.8818(2) Å, b=8.8774(3) Å, c=9.7892(4) Å, β=101.401(1)°, V=586.25(4) ų and Z=4. Its structure was characterized by Rietveld refinement of powder laboratory X-ray diffraction data. It consists of octahedral sheets that are held together by sheets of isolated Ge₂O₇ diorthogroups composed of two tetrahedra sharing a common vertex. It contains only one octahedral site occupied by In³⁺ and Tb⁺³ cations. The characteristic mirror plane in the thortveitite (Sc₂Si₂O₇) space group (C2/m, No. 12) is not present in this new compound. Besides, in InTbGe₂O₇, the Ge–O–Ge angle bridging two diorthogroups is 156.8(2)° as compared to the one in thortveitite, which is 180°. On the other hand, luminescent properties were observed when it is excited with 376.5 nm wavelength. The luminescence spectrum shows typical transitions from the ⁵D₄ multiplet belonging to the trivalent terbium ion.     

Sr2NiMoO6−δ as anode material for LaGaO3-based solid oxide fuel cell

The double-perovskite Sr₂NiMoO_6−δ (SNMO) was investigated as an anode material of a solid oxide fuel cell (SOFC). With a 300 μm thick La_0.9Sr_0.1Ga_0.8Mg_0.2O_3−σ (LSGM) disk as electrolyte and Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3−δ as the cathode, the SNMO anode showed power densities of 819 mW cm⁻² in hydrogen at 1123 K. Moreover, there was no buffer layer between anode and electrolyte, which would reduce design techniques and save design cost. After test no chemical reaction was discovered between anode and electrolyte. The anode exhibited good conductivity and the value was around 60 S cm⁻¹ in H₂. Also it had almost linear thermal expansion from room temperature to 1253 K and the average thermal expansion coefficient was about 12.14 × 10⁻⁶ K⁻¹, which was quite close to that of La_0.9Sr_0.lGa_0.8Mg_0.2O₃ (12.17 × 10⁻⁶ K⁻¹) electrolyte.     

An XRPD ab-initio structural determination of La2RuO5

The crystal structure of a new oxide, La₂RuO₅, was determined ab initio using conventional laboratory X-ray powder diffraction. Combining X-ray and electron diffraction techniques, we found that the new phase crystallized in the monoclinic system with the space group P2₁/c (SG no.14) and the cell parameters a=9.1878(2) Å, b=5.8313(2) Å, c=7.9575(2) Å and β=100.773(2)° (V=418.8 ų, Z=4). The structural determination with the Patterson method and Fourier difference syntheses and the final Rietveld refinement were performed by means of the JANA2000 program. The structure is built up from the regular stacking of a two octahedra thick [LaRuO₄]_∞ zigzag perovskite slab and an original 3.4 Å thick [LaO]_∞ slab which constitutes the key feature of this new structure.     

[As(V)As(III)O6]: An uncommon anion group in the crystal structure of K2Cu3(As2O6)2

The crystal structure of K₂Cu₃(As₂O₆)₂ was determined from single-crystal X-ray data by a direct method strategy and Fourier summations [a = 10.359(4) Å, B = 5.388(2)Å, C = 11.234(4) Å, β = 110.48(2)°; space group C2/m; Z = 2; R_w = 0.025 for 1199 reflections up to sin /λ = 0.81 Å⁻¹]. In detail, the structure consists of As(V)O₄ tetrahedra and As(III)O₃ pyramids linked by a common O corner atom to [As(V)As(III)O₆]⁴⁻ groups with symmetry m. The bridging bonds As(V)---O [1.749(3) Å] and As(III)---O [1.838(2) Å] are definitely longer than the other As(V)---O bonds [mean 1.669 Å] and As(III)---O bonds [1.764(2) Å, 2×]. The angle As(V)---O---As(III) is 123.0(1)°. The Cu atoms are [4 + 2]- and [4 + 1]-, and the K atom is [9]-coordinated to oxygen atoms. The As₂O₆ groups and the Cu coordination polyhedra are linked to sheets parallel to (001). These sheets are connected by the K atoms. Single crystals of K₂Cu₃(As₂O₆)₂ suitable for X-ray work were synthesized under hydrothermal conditions.