New triple molybdates Cs3LiCo2(MoO4)4 and Rb3LiZn2(MoO4)4, filled derivatives of the Cs6Zn5(MoO4)8 type

Two new isotypic triple molybdates, namely tri­cesium lithium dicobalt tetra­kis­(tetra­oxo­molybdate), Cs₃LiCo₂(MoO₄)₄, and tri­rubidium lithium dizinc tetra­kis­(tetra­oxo­molybdate), Rb₃LiZn₂(MoO₄)₄, crystallize in the non‐centrosymmetric cubic space group I3d and adopt the Cs₆Zn₅(MoO₄)₈ structure type. In the parent structure, the Zn positions have 5/6 occupancy, while they are fully occupied by statistically distributed M²⁺ and Li⁺ cations in the title compounds. In both structures, all corners of the (M_2/3Li_1/3)O₄ tetra­hedra (M = Co and Zn), having point symmetry , are shared with the MoO₄ tetra­hedra, which lie on threefold axes and share corners with three (M,Li)O₄ tetra­hedra to form open mixed frameworks. Large alkaline cations occupy distorted cubocta­hedral cavities with symmetry. The mixed tetra­hedral frameworks in the structures are close to those of mayenite (12CaO·7Al₂O₃) and the related compounds 11CaO·7Al₂O₃·CaF₂, wadalite (Ca₆Al₅Si₂O₁₆Cl₃) and Na₆Zn₃(AsO₄)₄·3H₂O, but the terminal vertices of the MoO₄ tetra­hedra are directed in opposite directions along the threefold axes compared with the configurations of Al(Si)O₄ or AsO₄ tetra­hedra. The cation arrangements in Cs₃LiCo₂(MoO₄)₄, Rb₃LiZn₂(MoO₄)₄ and Cs₆Zn₅(MoO₄)₈ repeat the structure of Y₃Au₃Sb₄, being stuffed derivatives of the Th₃P₄ type.     

LiFe(MoO4)2, LiGa(MoO4)2 and Li3Ga(MoO4)3

The structures of lithium iron dimolybdate, LiFe(MoO₄)₂, and lithium gallium dimolybdate, LiGa(MoO₄)₂, are shown to be isomorphous with each other. Their structures consist of segregated layers of LiO₆ bicapped trigonal bipyramids and Fe(Ga)O₆ octahedra separated and linked by layers of isolated MoO₄ tetrahedra. The redetermined structure of trilithium gallium trimolybdate, Li₃Ga(MoO₄)₃, shows substitional disorder on the Li/Ga site and consists of perpendicular chains of LiO₆ trigonal prisms and two types of differently linked Li/GaO₆ octahedra.     

Phase equilibrium in the Cs2MoO4-Bi2(MoO4)3-Zn(MoO4)2 system and the crystal structure of new triple molybdate Cs5BiZr(MoO4)6

The subsolidus region of the Cs₂MoO₄-Bi₂(MoO₄)₃-Zr(MoO₄) system was studied by X-ray powder diffraction. Quasi-binary sections were elucidated, and triangulation performed. Triple molybdates with the component ratios 5: 1: 2 (S ₁) and 2: 1: 4 (S ₂) were prepared for the first time. Crystals of cesium bismuth zirconium molybdate of the 5: 1: 2 stoichiometry (Cs₅BiZr(MoO₄)₆) were grown from fluxed melts with spontaneous nucleation. The composition and crystal structure of this triple molybdate were refined using X-ray diffraction data (collected on X8 APEX automated diffractometer, MoK _α radiation, 2348 F(hkl), R = 0.0226). The trigonal unit cell parameters were as follows: a = b = 10.9569(2), c = 39.804(4) Å, V = 4138.4(4) ų, Z = 6, space group R $ \bar 3 The subsolidus region of the Cs₂MoO₄-Bi₂(MoO₄)₃-Zr(MoO₄) system was studied by X-ray powder diffraction. Quasi-binary sections were elucidated, and triangulation performed. Triple molybdates with the component ratios 5: 1: 2 (S ₁) and 2: 1: 4 (S ₂) were prepared for the first time. Crystals of cesium bismuth zirconium molybdate of the 5: 1: 2 stoichiometry (Cs₅BiZr(MoO₄)₆) were grown from fluxed melts with spontaneous nucleation. The composition and crystal structure of this triple molybdate were refined using X-ray diffraction data (collected on X8 APEX automated diffractometer, MoK _α radiation, 2348 F(hkl), R = 0.0226). The trigonal unit cell parameters were as follows: a = b = 10.9569(2), c = 39.804(4) ?, V = 4138.4(4) ?³, Z = 6, space group R c. The mixed-metal three-dimensional framework in this structure is built of Mo tetrahedra and two sorts of (Bi,Zr)O₆ octahedra. Large interstices accommodate two sorts of cesium atoms. The Bi³⁺ and Zr⁴⁺ cation distributions over two positions were refined during structure solution. Original Russian Text ? B.G. Bazarov, T.V. Namsaraeva, R.F. Klevtsova, A.G. Anshits, T.A. Vereshchagina, R.V. Kurbatov, L.A. Glinskaya, K.N. Fedorov, Zh.G. Bazarova, 2008, published in Zhurnal Neorganicheskoi Khimii, 2008, Vol. 53, No. 9, pp. 1585–1589.     

Phase formation in the Rb2MoO4-Er2(MoO4)3-Hf(MoO4)2 system and the crystal structure of new triple molybdate Rb5ErHf(MoO4)6

The subsolidus region of the Rb₂MoO₄-Er₂(MoO₄)₃-Hf(MoO₄)₂ ternary salt system is studied using X-ray powder diffraction. A novel 5: 1: 2 triple molybdate, Rb₅ErHf(MoO₄)₆, is found to form in the system. Crystals of Rb₅ErHf(MoO₄)₆ are flux-grown under spontaneous nucleation conditions. The composition and crystal structure of Rb₅ErHf(MoO₄)₆ are refined in a single-crystal X-ray diffraction experiment (X8 APEX diffractometer, MoK _α radiation, 1753 reflections, R = 0.0183). The crystals are trigonal; a = 10.7511(1) Å, c = 38.6543(7) Å, V = 3869.31(9) ų, d _calc = 4.462 g/cm³, Z = 6, space group $R\bar 3c$ . The mixed three-dimensional framework of the structure is formed of MoO₄ tetrahedra, each sharing corners with two ErO₆ and HfO₆ octahedra. Two types of Rb atoms occupy large cavities of the framework. The distribution of the Er³⁺ and Hf⁴⁺ cation over two positions is refined in the course of structure solution.     

Phase equilibria in the systems Rb2MoO4-R2(MoO4)3-Hf(MoO4)2 (R = Al, In, Sc, Fe(III)) and the crystal structure of double molybdate RbFe(MoO4)2

The systems Rb₂MoO₄-R₂(MoO₄)₃-Hf(MoO₄)₂ have been investigated in the subsolidus region by X-ray powder diffraction, DTA, and IR spectroscopy. Triple molybdates of the composition 5: 1: 2 are formed in the systems with R = Al, In, Sc, and Fe. Molybdates of composition 5: 1: 3 and 1: 1: 1 are found in the iron(III)-containing system in addition to the 5: 1: 2 molybdate. Single crystals of the double molybdate RbFe(MoO₄)₂, which is formed in the Rb₂MoO₄-Fe₂(MoO₄)₃ system, have been grown. The structure of this double molybdate has been refined using X-ray diffraction data (X8 APEX automated diffractometer, MoK _α radiation, 373 F(hkl), R = 0.0287). The trigonal unit cell parameters are the following: a = b = 5.6655(2) Å, c = 7.5061(4) Å, V = 208.65(1) ų, Z = 1, ρ_calc = 3.670 g/cm³, space group R3m1. The structure is formed by layers of FeO₆ octahedra sharing corners with MoO₄ tetrahedra and RbO₁₂ icosahedra.     

Phase formation in Cs2MoO4-MMoO4-Zr(MoO4)2 (M = Mn, Mg, Co, Zn) systems and crystal structure of new double molybdates Cs2MnZr2(MoO4)6 and Cs2MnZr(MoO4)4

Subsolidus phase relations in the Cs₂MoO₄-MMoO₄-Zr(MoO₄)₂ (M = Mn, Zn) ternary systems were determined, and two groups of new isostructural triple molybdates were synthesized: Cs₂MZr(MoO₄)₄ and Cs₂MZr₂(MoO₄)₆ (M = Mn, Mg, Co, Zn). Cs₂MnZr₂(MoO₄)₆ and Cs₂MnZr(MoO₄)₄ crystals were grown by spontaneous flux crystallization and used in structure solution for both groups of compounds. The Cs₂MnZr₂(MoO₄)₆ structure (a =13.4322(2) ?, c = 12.2016(3) ?, group R3, Z = 3, R = 0.0367) is a new structure type characterized by a mixed three-dimensional framework built of corner-sharing MoO₄ tetrahedra and (M, Zr)O₆ octahedra where large channels are occupied by cesium cations. Cs₂MnZr₂(MoO₄)₄ (a =5.3890(1) ?, c = 8.0685(3) ?, space group P $ \bar 3 $ \bar 3 m1, Z = 0.5, R = 0.0247) has the layered glaserite-like KAl(MoO₄)₂ type structure, where Al³⁺ octahedral positions are randomly occupied by a 0.5M²⁺ + 0.5Zr⁴⁺ mixture.     

Binary molybdates K4M2+(MoO4)3 (M2+=Mg, Mn, Co) and crystal structure of K4Mn(MoO4)3

Binary molybdates K₄M²⁺ (MoO₄)₃ (M²⁺=Mg, Mn, Co) isostructural to triclinic \ga-K₄Zn(WO₄)₃ were synthesized, and optimal conditions for their spontaneous crystallization were found. It was established by XRPA and DTA that at 530°C the structure of the compound with cobalt undergoes a transition to the orthorhombic structure of K₄Zn(MoO₄)₃. The structure of K₄Mn(MoO₄)₃ was determined from single crystal diffraction data (a=7.613, b=9.955, c=10.156 Å,α=92.28,β=106.66,γ=105.58°, Z=2, space group $P\bar 1$ , R=0.030). In this compound, Mn has a higher coordination number (CN=5+1) than that of Zn inα-K₄Zn(WO₄)₃ (CN=4+1). The main structural feature is pairs of MnO₆ octahedra linked by the bridging MoO₄ tetrahedra into ribbons stretching along the a axis. The structure is compared with related structures of binary molybdates and other members of the alluaudite family.     

Subsolidus phase diagrams of the systems Cs2MoO4-R2(MoO4)3-Zr(MoO4)2, where R = Al, Sc, or In

The systems Cs₂MoO₄?R₂(MoO₄)₃?Zr(MoO₄)₂, where R = Al, Sc, or In, have been investigated in the subsolidus region by X-ray powder diffraction. Quasi-binary joins have been revealed, and triangulation has been carried out. Six new triple molybdates have been prepared with the component ratio equal to 1 : 1 : 1 (mol/mol) (S ₁) and 5 : 1 : 2 (S ₂). The crystal parameters for the 5 : 1 : 2 compounds have been determined, and the electrical properties of the 1 : 1 : 1 compounds have been investigated.     

Phase formation in the Li2MoO4-A2MoO4-NiMoO4 (A = K, Rb, Cs) systems, the crystal structure of Cs2Ni2(MoO4)3, and color characteristics of alkali-metal nickel molybdates

The subsolidus regions of the Li₂MoO₄-A₂⁺MoO₄-NiMoO₄ (A⁺ = K, Rb, Cs) systems at 510°C have been triangulated by the intersecting-joins method. The A₂MoO₄-Li₂Ni₂(MoO₄)₃, Li₂MoO₄-A₂Ni₂(MoO₄)₃, A₂Ni₂(MoO₄)₃-Li₂Ni₂(MoO₄)₃ (A = K, Rb, Cs), and ALiMoO₄-A₂Ni₂(MoO₄)₃ (A = K, Rb) joins have been investigated. The subsolidus phase formation study has also been completed by spontaneous flux crystallization. No triple salts have been identified, but only compounds belonging to the boundary binary systems. The crystal structure of Cs₂Ni₂(MoO₄)₃ (a = 10.7538 ?, Z = 4, space group P2₁3, R = 0.0082) belonging to the langbeinite type has been determined. It is built of a three-dimensional framework of vertexsharing MoO₄ tetrahedra and NiO₆ octahedra and cesium ions occupying large out-of-framework cavities. All alkali-metal nickel molybdates are yellow. These compounds are usable as pigments, as judged from their reflection spectra and calculated color characteristics, namely, colorfulness (C), lightness (L), and hue (H).     

Phase equilibria in the Tl2MoO4-Nd2(MoO4)3-Hf(MoO4)2 system and the crystal structure of double molybdate TlNd(MoO4)2

The Tl₂MoO₄-Nd₂(MoO₄)₃-Hf(MoO₄)₂ system was studied in the subsolidus region using X-ray powder diffraction. New triple molybdates were found to exist in this system: Tl₅NdHf(MoO₄)₆ (5: 1: 2), TlNdHf_0.5(MoO₄)₃ (1: 1: 1), and Tl₂NdHf₂(MoO₄)_6.5 (2: 1: 4). The first TlNd(MoO₄)₂ single crystals were grown from melt solutions with spontaneous nucleation. Their crystal structure was refined from X-ray diffraction data (Bruker X8 Apex automated diffractometer, MoK _α radiation, 386 F(hkl), R = 0.0136). The tetragonal unit cell parameters are as follows: a = 6.3000(2) Å, c = 9.5188(5) Å, V = 377.80(3) ų, Z = 2, ρ_calcd = 5.876 g/cm³, space group P4/nnc. The structure is a framework built of NdO₈ and TlO₈ tetragonal antiprisms linked via shared lateral edges and alternating in the checkerboard order. Layers share oxygen vertices with MoO₄ interlayer tetrahedra and are linked into the framework.     

Phase relations in the systems M2MoO4-Cr2(MoO4)3-Zr(MoO4)2 (M = Li, Na, or Rb)

Phase equilibria in the systems M₂MoO₄-Cr₂(MoO₄)₃-Zr(MoO₄)₂ (M = Li, Na, or Rb) were investigated by X-ray powder diffraction analysis, DTA, and IR spectroscopy. The subsolidus structure of the phase diagrams of the systems under study was established. Two phases are formed in the Rb₂MoO₄-Cr₂(MoO₄)₃-Zr(MoO₄)₂ system with the molar ratios of the starting components equal to 5: 1: 1 (S ₂) and 1: 1: 1 (S ₁). Proceeding from that the isostructurality of Rb₅FeHf(MoO₄)₆ and S ₂ the unit cell, parameters are determined for S ₂.     

Homogeneity regions of double molybdates in the Na2MoO4-MgMoO4 system and structures of triclinic Na1.51Mg2.245(MoO4)3 and Na1.66Mn2.17(MoO4)3

In the samples of the Na₂MoO₄-MgMoO₄ system quenched in the air at above 600°C, by powder X-ray diffraction two double molybdates of variable composition are detected: monoclinic alluaudite-like Na_4?2x Mg_1+x (MoO₄)₃ (0.05 ≤ x ≤ 0.35) and triclinic Na_2?2y Mg_2+y (MoO₄)₃ (0.10 ≤ y ≤ 0.40) isostructural to previously studied Na₂Mg₅(MoO₄)₆. Sodium-magnesium molybdate of the Li₃Fe(MoO₄)₃ structure type is not revealed in this system. By spontaneous flux crystallization, the crystals are obtained and the structures of two triclinic double molybdates of the Na₂Mg₅(MoO₄)₆ structure type (space group $P\bar 1$ , Z = 1) containing magnesium and manganese are determined. The results of the refinement of site occupancies made it possible to determine the composition of the studied crystals: for the compound with magnesium (Na)_0.5(Na_0.255□_0.745)(Na_0.755Mg_0.245)Mg₂(MoO₄)₃ or Na_1.51Mg_2.245(MoO₄)₃ (a = 6.9577(1) Å, b = 8.6330(2) Å, c = 10.2571(2) Å, α = 106.933(1)°, β = 104.864(1)°, γ = 103.453(1)°, R = 0.0188); for the compound with manganese (Na)_0.5(Na_0.33□_0.67)(Na_0.83Mn_0.17)Mn₂(MoO₄)₃ or Na_1.64Mn_2.17(MoO₄)₃ (a = 7.0778(2) Å, b = 8.8115(2) Å, c = 10.4256(2) Å, α = 106.521(1)°, β = 105.639(3)°, Γ = 103.233(1)°, R = 0.0175). The Na₂Mg₅(MoO₄)₆ structure is redetermined and it is shown that actually it corresponds to the composition Na_1.40Mg_2.30(MoO₄)₃.     

Drei neue Selenoborato-closo-dodekaborate: Synthesen und Kristallstrukturen von Rb8[B12(BSe3)6], Rb4Hg2[B12(BSe3)6] und Cs4Hg2[B12(BSe3)6]

Three Novel Selenoborato- closo -dodecaborates: Syntheses and Crystal Structures of Rb₈[B₁₂(BSe₃)₆], Rb₄Hg₂[B₁₂(BSe₃)₆], and Cs₄Hg₂[B₁₂(BSe₃)₆] The three selenoborates Rb₈[B₁₂(BSe₃)₆] (P1, a = 10.512(5) Å, b = 10.450(3) Å, c = 10.946(4) Å, α = 104.53(3)°, β = 91.16(3)°, γ = 109.11(3)°, Z = 1), Cs₄Hg₂[B₁₂(BSe₃)₆] (P1, a = 9.860(2) Å, b = 10.740(2) Å, c = 11.078(2) Å, α = 99.94(3)°, β = 90.81(3)°, γ = 115.97(3)°, Z = 1), and Rb₄Hg₂[B₁₂(BSe₃)₆] (P1, a = 9.593(2) Å, b = 10.458(2) Å, c = 11.131(2) Å, α = 99.25(3)°, β = 91.16(3)°, γ = 116.30(3)°, Z = 1) were prepared from the metal selenides, amorphous boron and selenium by solid state reactions at 700 °C. These new chalcogenoborates contain B₁₂ icosahedra completely saturated with six trigonal-planar BSe₃ entities functioning as bidentate ligands to form a persubstituted closo-dodecaborate anion. The two isotypic compounds Rb₄Hg₂[B₁₂(BSe₃)₆] and Cs₄Hg₂[B₁₂(BSe₃)₆] are the first selenoborate structures containing a transition metal which are characterized by single crystal diffraction.     

Synthese und Kristallstruktur zweier Formen von Ammoniummonomolybdat (NH4)2MoO4

Synthesis and Structure of Two Forms of Ammonium Monomolybdate (NH₄)₂MoO₄ Ammonium monomolybdate (NH₄)₂MoO₄ exists in two different polymorphic forms which differ in their lattice constants and in the arrangement of the ammonium cations relative to the molybdate anions. The ammonium molybdates (NH₄)₂MoO₄(mS60)¹⁾ and (NH₄)₂MoO₄(mP60)²⁾ are synthesized by the reaction of ammonia and (NH₄)₆[Mo₇O₂₄] · 4 H₂O. (NH₄)₂MoO₄(mS60) crystallizes isostructural to the potassium compound in space group C2/m (Nr. 12) and lattice constants a = 1263.6(3), b = 652.2(1) pm, c = 776.4(2) pm and β = 117.36(1)° (V = 568.3(2) · 10⁶ pm³) containig four formula units per unit cell (R = 0.0250). (NH₄)₂MoO₄(mP60) crystallizes monoclinic in space group P2₁/n (Nr. 14) and lattice constants a = 622.8(2), b = 777.0(1) pm, c = 1118.8(4) pm and β = 98.09(2)° (V = 536.0(3) · 10⁶ pm³) (R = 0.0205). The different arrangements of the polyhedra within the unit cell is caused by hydrogen bridges. A transition point was not yet determined.     

Crystal Structure of Ternary Molybdate Rb5FeHf(MoO4)6 — a New Phase in the Rb2MoO4-Fe2(MoO4)3-Hf(MoO4)2 System

Physicochemical analysis (XRPA, DTA) was used to study phase equilibria in a ternary salt system Rb₂MoO₄-Fe₂(MoO₄)₃-Hf(MoO₄)₂ in the subsolidus region. Ternary molybdates with compositions 5:1:3, 5:1:2, and 1:1:1 have been found and synthesized. Crystal and thermal characteristics have been determined. Single crystals of the ternary molybdate Rb₅FeHf(MoO₄)₆ with a composition of 5:1:2 were grown. The crystal structure of the compound was solved using X-ray diffractometry (CAD-4 automatic diffractometer, MoK _α radiation, 1766 F(hkl), R = 0.0298). Hexagonal crystals with unit cell dimensions: a = b = 10.124(1) Å, c =15.135(3) Å, V = 1343.4(4) ų, Z = 2, ρ_calc = 4.008 g/cm³, space group P6₃. The mixed three-dimensional framework of the structure is formed from two sorts of MoO₄ tetrahedra and Fe and Hf octahedra linked through their common O-vertices. Rubidium atoms of three varieties occupy the large voids of the framework.Original Russian Text Copyright © 2004 by B. G. Bazarov, R. F. Klevtsova, A. D. Tsyrendorzhieva, L. A. Glinaskaya, and Zh. G. Bazarova__________Translated from Zhurnal Strukturnoi Khimii, Vol. 45, No. 6, pp. 1038–1043, November–December, 2004.     

Li3Al(MoO4)3, a lyonsite molybdate

Trilithium aluminium trimolybdate(VI), Li₃Al(MoO₄)₃, has been grown as single crystals from α‐Al₂O₃ and MoO₃ in an Li₂MoO₄ flux at 998 K. This compound is an example of the well known lyonsite structure type, the general formula of which can be written as A₁₆B₁₂O₄₈. Because this structure can accomodate cationic mixing as well as cationic vacancies, a wide range of chemical compositions can adopt this structure type. This has led to instances in the literature where membership in the lyonsite family has been overlooked when assigning the structure type to novel compounds. In the title compound, there are two octahedral sites with substitutional disorder between Li⁺ and Al³⁺, as well as a trigonal prismatic site fully occupied by Li⁺. The (Li,Al)O₆ octahedra and LiO₆ trigonal prisms are linked to form hexagonal tunnels along the [100] axis. These polyhedra are connected by isolated MoO₄ tetrahedra. Infinite chains of face‐sharing (Li,Al)O₆ octahedra extend through the centers of the tunnels. A mixed Li/Al site, an Li, an Mo, and two O atoms are located on mirror planes.     

Investigation par analyse thermique differentielle du systeme Gd2(MoO4)3-Bi2(MoO4)3

The phase diagram of the system Gd₂(MoO₄)₃-Bi(MoO₄)₃ has been studied by differential thermal analysis (DTA). Sealed platinum tubes were used as sample holders, in order to prevent the loss of Bi₂O₃ and MoO₃ through volatilization at high temperature. Various solid solutions and new phases are reported: α-Gd_2-x-Bi_x(MoO₄)₃, β -Gd_2-x-Bi_x(MoO₄)₃, α-Bi_2-xGd_x(MoO₄)₃, 3Gd₂(MoO₄)₃·2Bi₂(MoO₄)₃, etc.     

Design and Syntheses of Three Novel Carbonate Halides: Cs3Pb2(CO3)3I,KBa2(CO3)2F,and RbBa2(CO3)2F

Three new carbonate halides, Cs₃Pb₂(CO₃)₃I, KBa₂(CO₃)₂F and RbBa₂(CO₃)₂F have been synthesized with hydrothermal and solid‐state methods. Cs₃Pb₂(CO₃)₃I is the first product in the lead carbonate iodides family; KBa₂(CO₃)₂F and RbBa₂(CO₃)₂F are the first two centrosymmetric compounds found in the alkaline–alkaline earth carbonate fluorides family. Cs₃Pb₂(CO₃)₃I crystallizes in a centrosymmetric space group C2/m, and exhibits a two‐ dimensional layered structure which is formed by [Cs₄Pb₄(CO₃)₆I₂]_∞ double‐layers consisting of [Pb₂(CO₃)₃I]_∞ single‐layers bridged by the Cs atoms. KBa₂(CO₃)₂F and RbBa₂(CO₃)₂F, which are isostructural, crystallize in a trigonal crystal system with a centric space group of R featuring a honeycomb‐like framework. First principle calculations indicate that Cs₃Pb₂(CO₃)₃I has a moderate birefringence and explain the difference between the band gaps of the title compounds from electron structures. The effects of cations and halogens on the structures and properties of the title compounds are also discussed.     

Goldreiche Auride mit Caesium: Cs1,34Rb0,66RbAu7 und Cs1,60Rb0,40RbAu7

Gold-rich Aurides with Caesium: Cs_1.34Rb_0.66RbAu₇ and Cs_1.60Rb_0.40RbAu₇ Cs_1,60Rb_0,40RbAu₇, Raumgruppe Cmmm, Z = 2, a = 5,677(1) Å, b = 13,273(3) Å, c = 7,288(1) Å, R1/wR2 = 0,0392/0,0892, Z(F) ≥ 2σ(F) = 700 and Z(Var.) = 23. Silver coloured, brittle single crystals of Cs_1.34Rb_0.66RbAu₇ and Cs_1.60Rb_0.40RbAu₇ were obtained by the reaction of CsN₃, RbN₃ and gold sponge at 903 K. The structures were determined from X-ray single-crystal diffractometry data: Cs_1.34Rb_0.66RbAu₇, space group Cmmm, Z = 2, a = 5.657(1) Å, b = 13.265(4) Å, c = 7.281(2) Å, R1/wR2 = 0.0373/0,0628, N(F) ≥ 2σ(F) = 818 and N(var.) = 23.     

New NASICON type oxyanion high capacity anode, Li2Co2(MoO4)3, for lithium-ion batteries: preliminary studies

We describe in this paper the lithium insertion/extraction behavior of a new NASICON type Li₂Co₂(MoO₄)₃ at a low potential and explored the possibility of considering this new oxyanion material as anode for lithium-ion batteries for the first time. Li₂Co₂(MoO₄)₃ was synthesized by a soft-combustion glycine-nitrate low temperature protocol. Test cells were assembled using composite Li₂Co₂(MoO₄)₃ as the negative electrode material and a thin lithium foil as the positive electrode material separated by a microporous polypropylene (Celgard® membrane) soaked in aprotic organic electrolyte (1 M LiPF₆ in EC/DMC). Electrochemical discharge down to 0.001 V from OCV (～3.5 V) revealed that about 35 Li⁺ could ^possibly be inserted into Li₂Co₂(MoO₄)₃ during the first discharge (reduction) corresponding to a specific capacity amounting to 1,500 mAh g^?1. This is roughly fourfold higher compared to that of frequently used graphite electrodes. However, about 24 Li⁺ could be extracted during the first charge. It is interesting to note that the same amount of Li⁺ could be inserted during the second Li⁺ insertion process (second cycle discharge) giving rise to a second discharge capacity of 1,070 mAh g^?1. It was also observed that a major portion of lithium intake occurs below 1.0 V vs Li/Li⁺, which is typical of anodes being used in lithium-ion batteries.