Synthesis and crystal structure of the palladium oxides NaPd3O4, Na2PdO3 and K3Pd2O4

NaPd₃O₄, Na₂PdO₃ and K₃Pd₂O₄ have been prepared by solid-state reaction of Na₂O₂ or KO₂ and PdO in sealed silica tubes. Crystal structures of the synthesized phases were refined by the Rietveld method from X-ray powder diffraction data. NaPd₃O₄ (space group Pm3¯n, a=5.64979(6) Å, Z=2) is isostructural to NaPt₃O₄. It consists of NaO₈ cubes and PdO₄ squares, corner linked into a three-dimensional framework where the planes of neighboring PdO₄ squares are perpendicular to each other. Na₂PdO₃ (space group C2/c, a=5.3857(1) Å, b=9.3297(1) Å, c=10.8136(2) Å, β=99.437(2)°, Z=8) belongs to the Li₂RuO₃-structure type, being the layered variant of the NaCl structure, where the layers of octahedral interstices filled with Na⁺ and Pd⁴⁺ cations alternate with Na₃ layers along the c-axis. Na₂PdO₃ exhibits a stacking disorder, detected by electron diffraction and Rietveld refinement. K₃Pd₂O₄, prepared for the first time, crystallizes in the orthorhombic space group Cmcm (a=6.1751(6) Å, b=9.1772(12) Å, c=11.3402(12) Å, Z=4). Its structure is composed of planar PdO₄ units connected via common edges to form parallel staggered PdO₂ strips, where potassium atoms are located between them. Magnetic susceptibility measurements of K₃Pd₂O₄ reveal a Curie-Weiss behavior in the temperature range above 80 K.     

Structural study of the NaCdVO4-Cd3V2O8 and CdO-V2O5 sections of the ternary system Na2O-CdO-V2O5

The NaCdVO₄-Cd₃V₂O₈ and CdO-V₂O₅ sections of the ternary system Na₂O-CdO-V₂O₅ have been studied and the crystal structures of Cd₃V₂O₈ and Cd₁₈V₈O₃₈ compounds were determined from single-crystal X-ray diffraction data. Cd₃V₂O₈ crystallizes with the maricite-type structure in space group Pnma, a=9.8133(10) Å, b=6.9882(10) Å, c=5.3251(10) Å and Z=4, whereas Cd₁₈V₈O₃₈ crystallizes in space group P1 with a new-type structure, a=8.5761(14), b=8.607(3), c=12.896(2) Å, α=95.64(1), β=102.45(1), γ=108.42(1)° and Z=1. The Cd₃V₂O₈ structure is made up of Cd1O₄ infinite chains of edge-sharing Cd1O₆ octahedra which are parallel to the b direction. The Cd1O₄ chains are linked together by VO₄ tetrahedra and strongly distorted Cd2O₄ tetrahedra. The structure of Cd₁₈V₈O₃₈ is based on an ordered three-dimensional framework of cadmium and vanadium polyhedra that share corners. The distorted CdO₆ octahedra, CdO₅ trigonal bipyramids and CdO₅ square pyramids share corners, edges or faces.     

Synthesis and crystal structure of new uranyl tungstates M2(UO2)(W2O8) (M=Na, K), M2(UO2)2(WO5)O (M=K, Rb), and Na10(UO2)8(W5O20)O8

The solid-state reactions of UO₃ and WO₃ with M₂CO₃ (M=Na, K, Rb) at 650°C for 5 days result, accordingly the starting stoichiometry, in the formation of M₂(UO₂)(W₂O₈) (M=Na (1), K (2)), M₂(UO₂)₂(WO₅)O (M=K (3), Rb (4)), and Na₁₀(UO₂)₈(W₅O₂₀)O₈ (5). The crystal structures of compounds 2, 3, 4, and 5 have been determined by single-crystal X-ray diffraction using Mo(Kα) radiation and a charge-coupled device detector. The crystal structures were solved by direct methods and Fourier difference techniques, and refined by a least-squares method on the basis of F² for all unique reflections. For (1), unit-cell parameters were determined from powder X-ray diffraction data. Crystallographic data: 1, monoclinic, a=12.736(4) Å, b=7.531(3) Å, c=8.493(3) Å, β=93.96(2)°, ρ_cal=6.62(2) g/cm³, ρ_mes=6.64(1) g/cm³, Z=4; 2, orthorhombic, space group Pmcn, a=7.5884(16) Å, b=8.6157(18) Å, c=13.946(3) Å, ρ_cal=6.15(2) g/cm³, ρ_mes=6.22(1) g/cm³, Z=8, R1=0.029 for 80 parameters with 1069 independent reflections; 3, monoclinic, space group P2₁/n, a=8.083(4) Å, b=28.724(5) Å, c=9.012(4) Å, β=102.14(1)°, ρ_cal=5.83(2) g/cm³, ρ_mes=5.90(2) g/cm³, Z=8, R1=0.037 for 171 parameters with 1471 reflections; 4, monoclinic, space group P2₁/n, a=8.234(1) Å, b=28.740(3) Å, c=9.378(1) Å, β=104.59(1)°, ρ_cal=6.13(2) g/cm³,  g/cm³, Z=8, R1=0.037 for 171 parameters with 1452 reflections; 5, monoclinic, space group C2/c, a=24.359(5) Å, b=23.506(5) Å, c=6.8068(14) Å, β=94.85(3)°, ρ_cal=6.42(2) g/cm³,  g/cm³, Z=8, R1=0.036 for 306 parameters with 5190 independent reflections. The crystal structure of 2 contains linear one-dimensional chains formed from edge-sharing UO₇ pentagonal bipyramids connected by two octahedra wide (W₂O₈) ribbons formed from two edge-sharing WO₆ octahedra connected together by corners. This arrangement leads to [UW₂O₁₀]²⁻ corrugated layers parallel to (001). Owing to the unit-cell parameters, compound 1 probably contains similar sheets parallel to (100). Compounds 3 and 4 are isostructural and the structure consists of bi-dimensional networks built from the edge- and corner-sharing UO₇ pentagonal bipyramids. This arrangement creates square sites occupied by W atoms, a fifth oxygen atom completes the coordination of W atoms to form WO₅ distorted square pyramids. The interspaces between the resulting [U₂WO₁₀]²⁻ layers parallel to plane are occupied by K or Rb atoms. The crystal structure of compound 5 is particularly original. It is based upon layers formed from UO₇ pentagonal bipyramids and two edge-shared octahedra units, W₂O₁₀, by the sharing of edges and corners. Two successive layers stacked along the [100] direction are pillared by WO₄ tetrahedra resulting in sheets of double layers. The sheets are separated by Na⁺ ions. The other Na⁺ ions occupy the rectangular tunnels created within the sheets. In fact complex anions W₅O₂₀¹⁰⁻ are built by the sharing of the four corners of a WO₄ tetrahedron with two W₂O₁₀ dimmers, so, the formula of compound 5 can be written Na₁₀(UO₂)₈(W₅O₂₀)O₈.     

A rare multi-coordinate tellurite, NH4ATe4O9·2H2O (ARb or Cs): The occurrence of TeO3, TeO4, and TeO5 Polyhedra in the same material

Two new tellurites, NH₄RbTe₄O₉·2H₂O and NH₄CsTe₄O₉·2H₂O have been synthesized and characterized. The compounds were synthesized hydrothermally, in near quantitative yields, using the alkali metal halide, TeO₂, and NH₄OH as reagents. The iso-structural materials exhibit layered, two-dimensional structural topologies consisting of TeO_x (x=3, 4, or 5) polyhedra separated by NH₄⁺, H₂O, Rb⁺ or Cs⁺ cations. Unique to these materials is the presence of TeO₃, TeO₄, and TeO₅ polyhedra. Thermogravimetric and infrared spectroscopic data are also presented. Crystal data: NH₄RbTe₄O₉·2H₂O: Monoclinic I2/a (no. 15), a=18.917(3) Å, b=6.7002(11) Å, c=21.106(5) Å, β=101.813(2)°, V=2618.5(9) Å³, Z=8; NH₄CsTe₄O₉·2H₂O: Monoclinic I2/a (no. 15), a=18.9880(12) Å, b=6.7633(4) Å, c=21.476(2) Å, β=102.3460(10)°, V=2694.2(3) Å³, Z=8.     

Synthesis, structure and magnetic properties of the new mixed-valence vanadate Na2SrV3O9

The new complex oxide Na₂SrV₃O₉ was synthesized and investigated by means of X-ray diffraction, electron microscopy and magnetic susceptibility measurements. This oxide has a monoclinic unit cell with parameters a=5.416(1) Å, b=15.040(3) Å, c=10.051(2) Å, β=97.03(3)°, space group P2₁/c and Z=4. The crystal structure of Na₂SrV₃O₉, as determined from X-ray single-crystal data, is built up from isolated chains formed by square V⁴⁺O₅ pyramids. Neighboring pyramids are linked by two bridging V⁵⁺O₄ tetrahedra sharing a corner with each pyramid. The Na and Sr atoms are situated between the chains. Electron diffraction and HREM investigations confirmed the crystal structure. The temperature dependence of the susceptibility indicates low-dimensional magnetic behavior with a sizeable strength of the magnetic intra-chain exchange J of the order of 80 K, which is very likely due to superexchange through the two VO₄ tetrahedra linking the magnetic V⁴⁺ cations.     

Synthesis, characterization and dielectric properties of new unidimensional quaternary tellurites: LaTeNbO6, La4Te6Nb2O23, and La4Te6Ta2O23

Three new tellurites, LaTeNbO₆ and La₄Te₆M₂O₂₃ (M=Nb or Ta) have been synthesized, as bulk phase powders and crystals, by using La₂O₃, Nb₂O₅ (or Ta₂O₅), and TeO₂ as reagents. The structures of LaTeNbO₆ and La₄Te₆Ta₂O₂₃ were determined by single crystal X-ray diffraction. LaTeNbO₆ consists of one-dimensional corner-linked chains of NbO₆ octahedra that are connected by TeO₃ polyhedra. La₄Te₆M₂O₂₃ (M=Nb or Ta) is composed of corner-linked chains of MO₆ octahedra that are also connected by TeO₄ and two TeO₃ polyhedra. In all of the reported materials, Te⁴⁺ is in an asymmetric coordination environment attributable to its stereo-active lone-pair. Infrared, thermogravimetric, and dielectric analyses are also presented. Crystallographic information: LaTeNbO₆, triclinic, space group P−1, a=6.7842(6) Å, b=7.4473(6) Å, c=10.7519(9) Å, α=79.6490(10)°, β=76.920(2)°, γ=89.923(2)°, Z=4; La₄Te₆Ta₂O₂₃, monoclinic, space group C2/c, a=23.4676(17) Å, b=12.1291(9) Å, c=7.6416(6) Å, β=101.2580(10)°, Z=4.     

Formation and structural refinements of tunneled intergrowth phases in the Ga2O3-In2O3-SnO2-TiO2 system

Over 100 samples were prepared as (Ga,In)₄(Sn,Ti)_n−4O_2n−2, n=6, 7, and 9 by solid-state reaction at 1400 °C and characterized by X-ray diffraction. Nominally phase-pure beta-gallia-rutile intergrowths were observed in samples prepared with n=9 (0.17?x?0.35 and 0?y?0.4) as well as in a few samples prepared with n=6 and 7. Rietveld analysis of neutron time-of-flight powder diffraction data were conducted for three phase-pure samples. The n=6 phase Ga_3.24In_0.76Sn_1.6Ti_0.4O₁₀ is monoclinic, P2/m, with Z=2 and a=11.5934(3) Å, b=3.12529(9) Å, c=10.6549(3) Å, β=99.146(1)°. The n=7 phase Ga_3.24In_0.76Sn_2.4Ti_0.6O₁₂ is monoclinic, C2/m, with Z=2 and a=14.2644(1) Å, b=3.12751(2) Å, c=10.6251(8) Å, β=108.405(1)°. The n=9 phase Ga_3.16In_0.84Sn₄TiO₁₆ is monoclinic, C2/m, with Z=2 a=18.1754(2) Å, b=3.13388(3) Å, c=10.60671(9) Å, β=102.657(1)°. All of the structures are similar in that they possess distorted hexagonal tunnels parallel to the [010] vector.     

Synthesis crystal structure and ionic conductivity of Ca0.5Bi3V2O10 and Sr0.5Bi3V2O10

Two new compounds Ca_0.5Bi₃V₂O₁₀ and Sr_0.5Bi₃V₂O₁₀ have been synthesized in the ternary system: MO-Bi₂O₃-V₂O₅ system (M=M²⁺). The crystal structure of Sr_0.5Bi₃V₂O₁₀ has been determined from single crystal X-ray diffraction data, space group and Z=2, with cell parameters a=7.1453(3) Å, b=7.8921(3) Å, c=9.3297(3) Å, α=106.444(2)°, β=94.088(2)°, γ=112.445(2)°, V=456.72(4) Å³. Ca_0.5Bi₃V₂O₁₀ is isostructural with Sr_0.5Bi₃V₂O₁₀, with, a=7.0810(2) Å, b=7.8447(2) Å, c=9.3607(2) Å, α=106.202(1)°, β=94.572(1)°, γ=112.659(1)°, V=450.38(2) Å³ and its structure has been refined by Rietveld method using powder X-ray data. The crystal structure consists of infinite chains of (Bi₂O₂) along c-axis formed by linkage of BiO₈ and BiO₆ polyhedra interconnected by MO₈ polyhedra forming 2D layers in ac plane. The vanadate tetrahedra are sandwiched between these layers. Conductivity measurements give a maximum conductivity value of 4.54×10⁻⁵ and 3.63×10⁻⁵ S cm⁻¹ for Ca_0.5Bi₃V₂O₁₀ and Sr_0.5Bi₃V₂O₁₀, respectively at 725 °C.     

Synthesis, crystal structure, and nonlinear optical properties of Bi2Cu5B4O14

Bi₂Cu₅B₄O₁₄ crystallizes in the noncentrosymmetric triclinic space group P1 (No. 1) with cell parameters a=10.1381(11) Å, b=9.3917(11) Å, c=3.4566(4) Å, α=105.570(2)°, β=92.275(2)°, γ=107.783(2)°, Z=1 and R₁=0.0401 and wR₂=0.0980. It is a layered structure that is built up from sheets of rectangular CuO₄ and trigonal BO₃ groups. The sheets are connected by infinite chains of edge shared BiO₆ polyhedra that intersect the bc plane at an angle slightly greater than 90°. The second-harmonic generation efficiency of Bi₂Cu₅B₄O₁₄, using 1064 nm radiation, is about one half times that of KH₂PO₄.     

Synthesis, crystal structure and optical properties of a novel sodium lead pentaborate, NaPbB5O9

A novel sodium lead pentaborate, NaPbB₅O₉, has been successfully synthesized by standard solid-state reaction. The single-crystal X-ray structural analysis showed that NaPbB₅O₉ crystallizes in the monoclinic space group P2₁/c with a=6.5324(10) Å, b=13.0234(2) Å, c=8.5838(10) Å, β=104.971(10)°, and Z=4. The crystal structure is composed of double ring [B₅O₉]³⁻ units, [PbO₇] and [NaO₇] polyhedra. [B₅O₉]³⁻ groups connect with each other forming two-dimensional infinite _∞[B₅O₉]³⁻ layers, while [PbO₇] and [NaO₇] polyhedra are located between the layers. [PbO₇] polyhedra linked together via corner-sharing O atom forming novel infinite _∞[PbO₆] chains along the c axis. The thermal behavior, IR spectrum and the optical diffuse reflectance spectrum of NaPbB₅O₉ were reported.     

The study of Bi3B5O12: synthesis, crystal structure and thermal expansion of oxoborate Bi3B5O12

The paper presents a new data on the crystal structure, thermal expansion and IR spectra of Bi₃B₅O₁₂. The Bi₃B₅O₁₂ single crystals were grown from the melt of the same stoichiometry by Czochralski technique. The crystal structure of Bi₃B₅O₁₂ was refined in anisotropic approximation using single-crystal X-ray diffraction data. It is orthorhombic, Pnma, a=6.530(4), b=7.726(5), c=18.578(5) Å, V=937.2(5) Å³, Z=4, R=3.45%. Bi³⁺ atoms have irregular coordination polyhedra, Bi(1)O₆ (d(B-O)=2.09-2.75 Å) and Bi(2)O₇ (d(B-O)=2.108-2.804 Å). Taking into account the shortest bonds only, these polyhedra are considered here as trigonal Bi(1)O₃ (2.09-2.20 Å) and tetragonal Bi(2)O₄ (2.108-2.331 Å) irregular pyramids with Bi atoms in the tops of both pyramids. The BiO₄ polyhedra form zigzag chains along b-axis. These chains alternate with isolated anions [B₂^IVB₃^IIIO₁₁]⁷⁻ through the common oxygen atoms to form thick layers extended in ab plane. A perfect cleavage of the compound corresponds to these layers and an imperfect one is parallel to the Bi-O chains. The Bi₃B₅O₁₂ thermal expansion is sharply anisotropic (α₁₁≈α₂₂=12, α₃₃=3×10⁻⁶ °C⁻¹) likely due to a straightening of the flexible zigzag chains along b-axis and decreasing of their zigzag along c-axis. Thus the properties like cleavage and thermal expansion correlate to these chains.     

K2Mo4O13 phases prepared by hydrothermal synthesis

Hydrothermal synthesis in the K-Mo oxide system was investigated as a function of the pH of the reaction medium. Four compounds were formed, including two K₂Mo₄O₁₃ phases. One is a new low-temperature polymorph, which crystallizes in the orthorhombic, space group Pbca, with Z=8 and unit cell dimensions a=7.544(1) Å, b=15.394(2) Å, c=18.568(3) Å. The other is the known triclinic K₂Mo₄O₁₃, whose structure was re-determined from single crystal data; its cell parameters were determined as a=7.976(2) Å, b=8.345(2) Å, c=10.017(2) Å, α=107.104(3)°, β=102.885(3)°, γ=109.760(3)°, which are the standard settings of the crystal lattice. The orthorhombic phase converts endothermically into triclinic phase at ca. 730 K with a heat of transition of 8.31 kJ/mol.     

Ce10[Si10O9N17]Br, Nd10[Si10O9N17]Br and Nd10[Si10O9N17]Cl oxonitridosilicate halides with a new layered structure type

The isotypic oxonitridosilicate halides Ce₁₀[Si₁₀O₉N₁₇]Br, Nd₁₀[Si₁₀O₉N₁₇]Br and Nd₁₀[Si₁₀O₉N₁₇]Cl were obtained by the reaction of the respective lanthanide metals, their oxides and halides with “Si(NH)₂” in a radiofrequency furnace at temperatures around 1800 °C, using CsBr, resp. CsCl, as a flux. The crystal structures were determined by single-crystal X-ray diffraction (Pbam, no. 55, Z=2; Ce/Br: a=10.6117(9) Å, b=11.2319(10) Å, c=11.688(8) Å, R1=0.0356; Nd/Br: a=10.523(2) Å, b=11.101(2) Å, c=11.546(2) Å, R1=0.0239; Nd/Cl: a=10.534(2) Å, b=11.109(2) Å, c=11.543(2) Å, R1=0.0253) and represent a new layered structure type. The structure refinements were performed utilizing an O/N-distribution model according to Paulings rules, i.e. nitrogen was positioned on all bridging sites and mixed O/N-occupation was assumed on the terminal sites resulting in charge neutrality of the compounds. The layers consist of condensed [SiN₂(O/N)₂] and [SiN₃(O/N)] tetrahedra of Q² and Q³ type. The chemical composition of the compounds was derived from chemical analyses for Nd₁₀[Si₁₀O₉N₁₇]Br and electron probe micro analyses (EPMA) for all three compounds. The results of IR spectroscopic investigations are reported.     

Structural studies on a high-pressure polymorph of NaYSi2O6

High-pressure synthesis experiments in the system Na₂O-Y₂O₃-SiO₂ revealed the existence of a previously unknown polymorph of NaYSi₂O₆ or Na₃Y₃[Si₃O₉]₂ which was quenched from 3.0 GPa and 1000 °C. Structural investigations on this modification have been performed using single-crystal X-ray diffraction data collected at ambient conditions. Furthermore, unpolarized micro-Raman spectra have been obtained from single-crystal material. The high-P modification of NaYSi₂O₆ crystallizes in the centrosymmetric space group C2/c with 12 formula units per cell (a=8.2131(9) Å, b=10.3983(14) Å, c=17.6542(21) Å, β=100.804(9)°, V=1481.0(3) Å³, R(|F|)=0.033 for 1142 independent observed reflections) and belongs to the group of cyclo-silicates. Basic building units are isolated three-membered [Si₃O₉] rings located in layers parallel to (010). Within a single layer the rings are concentrated in strings parallel to [100]. The sequence of directedness of up (U) or down (D) pointing tetrahedra of a single ring is UUU or DDD, respectively. Stacking of the layers parallel to b results in the formation of a three-dimensional structure in which yttrium and sodium cations are incorporated for charge compensation. In more detail, four non-tetrahedral cation positions can be differentiated which are coordinated by 6 and 8 oxygen ligands. Refinements of the site occupancies did not reveal any indication for mixed Na-Y populations on these positions. Finally, several geometrical parameters of rings occurring in cyclo-trisilicate structures have been compiled and are discussed.     

Structure determination of Na3DySi6O15 and crystal chemistry of zektzerite related compounds

The crystal structure of Na₃DySi₆O₁₅ has been solved and refined to an R₁=2.97% (wR₂=8.25%) for 1311 independent reflections. The compound was found to crystallize within the orthorhombic system with the space group Cmca (Z=8) and the lattice parameters: a=14.590(7) Å, b=17.813(4) Å, c=10.519(2) Å, V=2734.0 Å³, D_cal=3.11 g/cm³. The structure of Na₃DySi₆O₁₅ is a filled variant of the zektzerite with S like corrugated double chains of [SiO₄] tetrahedral, connected via Na⁺ and Dy³⁺ cations and running parallel to c-axis. The three-dimensional network results from the packing of these chains along [100] by skewering them in rods represented by the tunnels delimited by the S shape of the silicate chains. One of the main peculiar features of the Na₃DySi₆O₁₅ structure is the location of Na⁺ in tetrahedral sites with rather short Na-O bond lengths (2×2.243 and 2×2.262 Å).     

Subsolidus phase relations in Na2O-CuO-Sb2On system and crystal structure of new sodium copper antimonate Na3Cu2SbO6

Subsolidus phase relation studies in the NaSb₃O₇-Na₃SbO₄-CuO-CuSb₂O₆ quadrangle of Na₂O-CuO-Sb₂O_n system at 1123-1173 K revealed the formation of one new compound Na₃Cu₂SbO₆. It is a superstructure derived from α-NaFeO₂ type, space group C2/m, lattice constants: a=5.6759(1) Å, b=8.8659(1) Å, c=5.8379(1) Å, β=113.289(1)°. All ions are in octahedral environment, but CuO₆ polyhedron exhibits strong elongation due to Jahn-Teller effect (Cu-O: 2.000(2) Å×2, 2.021(2) Å×2, 2.494(3) Å×2), whereas SbO₆ octahedron is almost regular. The relationship to other similar superlattices is discussed.     

Structural refinement of T2Mo3O8 (T=Mg, Co, Zn and Mn) and anomalous valence of trinuclear molybdenum clusters in Mn2Mo3O8

Crystal structure of a series of mixed-metal oxides, T₂Mo₃O₈ (T=Mg, Co, Zn and Mn; P6₃mc; a=5.7628(1) Å, c=9.8770(3) Å for Mg₂Mo₃O₈; a=5.7693(3) Å, c=9.9070(7) Å for Co₂Mo₃O₈; a=5.7835(2) Å, c=9.8996(5) Å for Zn₂Mo₃O₈; a=5.8003(2) Å, c=10.2425(5) Å for Mn₂Mo₃O₈) was investigated by X-ray diffraction on single crystals. Structural analysis, magnetization measurements, X-ray photoemission spectroscopy and cyclic voltammetry showed that the Mn ions at the tetrahedral and octahedral sites in Mn₂Mo₃O₈ adopt different valences of +2 and 2+δ (δ>0), respectively. The formal valence of the Mo₃ in Mn₂Mo₃O₈ is 12−δ to retain electric neutrality of the compound. In contrast, the T ions and Mo₃ in T₂Mo₃O₈ (T=Mg, Co and Zn) adopt the valences of +2 and +12, respectively.     

Preparation, crystal structure, and magnetic studies of Na3Fe2Mo5O16, a new oxide containing Mo3O13 clusters

The complex oxide Na₃Fe₂Mo₅O₁₆ has been synthesized, and its crystal structure was determined by single-crystal X-ray diffraction (space group (SG) P-3m1; a=5.7366(6) Å, c=22.038(3) Å; Z=2). The compound can be considered as a new structure type containing Mo₃O₁₃ cluster units, which can be derived from the Na₂In₂Mo₅O₁₆ structure model by doubling of the cell along the c-axis. Na₃Fe₂Mo₅O₁₆ crystallizes in centrosymmetric SG (P-3m1) and the positions of the sodium atoms are fully occupied in contrast to the proposed Na₂In₂Mo₅O₁₆ model SG (P3m1). Magnetic properties of Na₃Fe₂Mo₅O₁₆ were studied by superconducting quantum interference device measurements, revealing antiferromagnetic ordering below Tχ_max=10(1) K. Thermal stability in air was investigated by in situ high-temperature X-ray powder diffraction. Structural relationships to Na₂In₂Mo₅O₁₆ and NaFe(MoO₄)₂ are discussed.     

A new 2212-type stair like structure: Bi14Sr21Fe12O61, m=5 member of the generic [Bi2Sr3Fe2O9]m[Bi4Sr6Fe2O16] family

A new oxide, Bi₁₄Sr₂₁Fe₁₂O_61, with a layered structure derived from the 2212 modulated type structure Bi₂Sr₃Fe₂O₉, was isolated. It crystallizes in the I2 space group, with the following parameters: a=16.58(3) Å, b=5.496(1) Å, c=35.27(2) Å and β=90.62°. The single crystal X-ray structure determination, coupled with electron microscopy, shows that this ferrite is the m=5 member of the [Bi₂Sr₃Fe₂O₉]_m[Bi₄Sr₆Fe₂O₁₆] collapsed family. This new collapsed structure can be described as slices of 2212 structure of five bismuth polyhedra thick along , shifted with respect to each other and interconnected by means of [Bi₄Sr₆Fe₂O₁₆] slices. The latter are the place of numerous defects like iron or strontium for bismuth substitution; they can be correlated to intergrowth defects with other members of the family.