A Mixed-Valent Molybdenotungsten Monophosphate with a Tunnel Structure: Nax(Mo, W)2O3(PO4)2

A mixed-valent molybdenotungstophosphate, Na_x(Mo, W)₂O₃(PO₄)₂ (x 0.75) has been isolated for the first time. It crystallizes in the space group P 2₁/m with a = 7.200(1) Å, b = 6.369(1) Å, c = 9.123(1) Å, and β = 106.29(1)°. Its structure consists of M₂PO₁₃ units built up of two M O₆ octahedra (M = Mo, W) and one PO₄ tetrahedron sharing their apices as already observed in several molybdenum phosphates. These units share their apices with PO₄ tetrahedra forming [M₂P₂O₁₅]_∞ chains running along . The host lattice [(Mo, W)₂P₂O₁₁]_∞ can be described by the assemblage of such chains or by the assemblage of [MPO₈]_∞ chains running along , in which one PO₄ tetrahedron alternates with one MO₆ octahedron. The tridimensional framework [Mo, WP₂O₁₁]_∞ delimits tunnels running along , occupied by sodium with two kinds of coordination, 6 and 5. The distribution of the different species, in the octahedral sites according to the formulation Na_0.75(Mo^VI_0.42W^VI_0.58)_M1 (Mo^V_0.75W^VI_0.25)₂O₃(PO₄)₂, is discussed.     

Isomorphism and phase diagram of the Pb5(PO4)3Cl-Pb5(VO4)3Cl system

Compounds of composition Pb₅(P _x V_1−x O₄)₃Cl (0 ≤ x ≤ 1), which are synthetic analogues of minerals pyromorphite, vanadinite, and endlichite, were synthesized for the first time by high-temperature solid-phase reactions. X-ray diffraction and IR spectroscopy were used to determine the structure of the compounds and revealed complete miscibility in the solid phase of the Pb₅(PO₄)₃Cl-Pb₅(VO₄)₃Cl binary system. Adiabatic reaction calorimetry was used to determine standard enthalpies of mixing and formation and showed that the regular solutions model is applicable to the Pb₅(PO₄)₃Cl-Pb₅(VO₄)₃Cl system. Differential thermal analysis in tandem with high-temperature X-ray diffraction was used to study the phase diagram and characterize phase transitions.     

A Raman spectroscopic study of the phosphate mineral pyromorphite Pb5(PO4)3Cl

A series of selected pyromorphite minerals Pb₅(PO₄)₃Cl from different Australian localities has been studied by Raman spectroscopy complemented with selected infrared spectroscopy. The Raman spectrum of unsubstituted pyromorphite shows a single band at around 920 cm⁻¹ but for the natural minerals two bands at 919 and ∼932 cm⁻¹ attributed to the ν₁ (PO₄)³⁻ stretching vibration. The observation of multiple bands is attributed to the non-equivalence of phosphate units in the pyromorphite structure and the reduction in symmetry of the (PO₄)³⁻ units. This symmetry reduction is confirmed by the observation of multiple bands in both the ν₄ bending region (500–595 cm⁻¹) and the ν₂ bending region (350–500 cm⁻¹). The presence of isomorphic substitution of (PO₄)³⁻ by (AsO₄)³⁻ units is identified by the ν₁ symmetric stretching bands at around 824 and 851 cm⁻¹ and the ν₂ bending region around 331 and 354 cm⁻¹. Contrary to expectation Raman bands in the 3320–3700 cm⁻¹ region are observed and assigned to OH stretching bands of OH units resulting from the substitution of chloride anions in the pyromorphite structure. This study brings in to question the actual formula of natural pyromorphite as it is better represented as Pb₅(PO₄,AsO₄)₃(Cl,OH) · xH₂O.     

Synthesis and structure investigation of the Pb3V(PO4)3 eulytite

Lead vanadium phosphate Pb₃V(PO₄)₃ was synthesized by solid state reaction and characterized by X-ray single crystal and powder diffraction, electron microscopy, and magnetic susceptibility measurements. The crystal structure model of Pb₃V(PO₄)₃ was refined using X-ray single crystal data (a=10.127(1)Å, S.G. Z=4). The compound has an eulytite-like structure and its average structure model may be presented as a three-dimensional network formed by strongly distorted mixed (Pb/V^III) metal-oxygen octahedra connected by edge sharing and forming corrugated chains. The octahedra are additionally linked by tetrahedral phosphate groups via corner sharing. Lead and vanadium atoms randomly occupy two close positions in the octahedra. The electron microscopy study revealed the presence of a rhombohedral superstructure with and indicating ordering in the structure. The same type of superstructure was found by us for two another lead-containing eulytite Pb₃Fe(PO₄)₃ where Fe⁺³ has an ionic radius close to that of V⁺³. Magnetic susceptibility measurements revealed Curie-Weiss behavior for the Pb₃V(PO₄)₃ compound.     

A new three-dimensional cobalt phosphate: Co5(OH2)4(HPO4)2(PO4)2

A three-dimensional (3D) cobalt phosphate: Co₅(OH₂)₄(HPO₄)₂(PO₄)₂ (1), has been synthesized by hydrothermal reaction and characterized by single-crystal X-ray diffraction, thermogravimetric analysis, and magnetic techniques. The title compound is a template free cobalt phosphate. Compound 1 exhibits a complex net architecture based on edge- and corner-sharing of CoO₆ and PO₄ polyhedra. The magnetic susceptibility measurements indicated that the title compound obeys Curie-Weiss behavior down to a temperature of 17 K at which an antiferromagnetic phase transition occurs.     

Structure and thermal expansion of LiGe2(PO4)3

LiGe₂(PO₄)₃ belongs to the Nasicon-type family. Room-temperature structure has been determined on a single crystal from 3D X-ray data. Thermal evolution of this structure has been established from neutron powder diffraction data between 300 and 1000 K using the Rietveld method. The thermal expansion is positive along the c-axis, whereas shrinking is observed along the a-axis below 900 K, followed by dilatation. The atomic displacements noted with increasing temperature are consistent with a model proposed for NaZr₂(PO₄)₃.     

Structure cristalline de Cu4(PO4)2O

Cu₄(PO₄)₂O is a new copper-rich phosphate. The preparation is described. The unit cell is triclinic, $\text{P}\text{1}$, with a = 7.528 Å, b = 8.090 Å, c = 6.272 Å; α = 113.68°, β = 81.56°, γ = 105.77°. The structure was solved from 1526 independent reflections using Patterson and Fourier syntheses. The final R value is 0.041 for the 1217 strongest reflections. Copper sites form a three-dimensional framework. The structure consists of homogeneous layers of copper and oxygen atoms parallel to the (012) plane. Phosphorus atoms are inserted between copper and oxygen layers.     

Structure and luminescence properties of silver-doped NaY(PO3)4 crystal

Single crystals of NaY(PO₃)₄ and Ag_0.07Na_0.93Y(PO₃)₄ have been synthesized by flux method. These new compounds turned out to be isostructural to NaLn(PO₃)₄, with Ln=La, Nd, Gd and Er [monoclinic, P2₁/n, a=7.1615(2) Å, b=13.0077(1) Å, c=9.7032 (3) Å, β=90.55 (1)°, V=903.86(14) Å³ and Z=4]. The structure is based upon long polyphosphate chains running along the shortest unit-cell direction and made up of PO₄ tetrahedra sharing two corners, linked to yttrium and sodium polyhedra. Infrared and Raman spectra at room temperature confirms this atomic arrangement. The luminescence of silver ions was reported in metaphosphate of composition Ag_0.07Na_0.93Y(PO₃)₄. One luminescent centre was detected and assigned to single Ag⁺ ions.     

Crystal structures of phosphomolybdyl salts: Pb(MoO2)2(PO4)2 and Ba(MoO2)2(PO4)2

Crystal structures of Pb(MoO₂)₂(PO₄)₂ and Ba(MoO₂)₂(PO₄)₂ were determined. Both compounds contain the molybdyl group MoO₂. The monoclinic unit-cell parameters are a = 6.353(7), b = 12.289(4), c = 11.800 Å, β = 92°56(6), and Z = 4 for the lead salt and a = 6.383(8), b = 7.142(7), c = 9.953(8) Å, β = 95°46(8), and Z = 2 for the barium salt. $\text{P2}{}_1\text{c}$ is the common space group. The R values are respectively R = 0.027 and R = 0.031 for 1964 and 1714 independent reflections. The frameworks built up by a three-dimensional network of monophosphate PO₄ and molybdyl MoO₂ groups are similar, characterized mainly by corner-sharing PO₄ and MoO₆ polyhedra. Two oxygen atoms of each MoO₆ group are bonded to the molybdenum atom only as in other molybdyl salts.     

A new iron oxophosphate SrFe3(PO4)3O with chain-like structure

A new strontium iron oxophosphate SrFe₃(PO₄)₃O was synthesized by the solid state method and its structure was studied by single-crystal X-ray and electron diffraction, high-resolution electron microscopy, Mössbauer and IR spectroscopy. The compound crystallizes in a monoclinic system (space group P2₁/m) with unit-cell parameters: a = 7.5395(7), b = 6.3476(7) c = 10.3161(13) Å, β = 99.740(9)°. The structure of SrFe₃(PO₄)₃O represents a new structural type and is made up of isolated PO₄ tetrahedra and FeO_n polyhedra connected via common vertices and edges to form a 3D framework. Iron cations occupy three crystallographically independent sites with different oxygen environment: Fe1 and Fe2 occupy two octahedral sites, and Fe3 is five-coordinated. Two particularities of this structure are remarkably mentioned: the isolated {FeO₆}_n octahedral chains along the b direction and the five coordinated environment for the Fe3 position. Mössbauer spectroscopy confirmed the presence of only high-spin Fe³⁺ cations in two types of coordination environment. The IR-data show the presence of only PO₄³⁻ groups.     

Crystal structure of cerium(III) diammonium polyphosphate (NH4)2Ce(PO3)5

Cerium(III) diammonium polyphosphate, (NH₄)₂Ce(PO₃)₅, is triclinic P1 with the following unit cell dimensions: a = 7.241(5) Å, b = 13.314(8) Å, c = 7.241(5)Å, α = 90.35(5)°, β′ = 107.50(5)°, γ = 90.28(5)°, and Z = 2, V = 665.7 ų, D_x = 2.85 g/cm³. The crystal structure of this new type of polyphosphate has been solved and refined from 4130 independent reflections to a final R value 0.029. The most interesting feature of this salt is the existence of two infinite crystallographically nonequivalent (PO₃)^?_∞ chains, one running parallel to the a axis, the other along the c axis, both with a period of five tetrahedra. This compound seems to be the first example of a long chain polyphosphate with crystallographic independent chains.     

The crystal structure of Ca3Cu3(PO4)4

Single crystals of Ca₃Cu₃(PO₄)₄ synthesized hydrothermally at 420°C and 55 kpsi (3.8 kbar) were found to occur in the space group $\text{P2}{}_1\text{a}$ (No. 14) with a = = 17.619(2), b = 4.8995(4), c = 8.917(1)Å, β = 124.08(1)°, and Z = 2. Full-matrix least-squares refinement of the structure using diffractometer data converged to a final anisotropic R = 0.037 (R_w = 0.046). The two calcium atoms are in six- and nine-coordination and the two copper-containing polyhedra (four- and five-coordinated) are similar to those previously found in Cu₃(PO₄)₂.     

Etude des propriétés de conduction électrique des polyphosphates: Li3Ba2(PO3)7, LiPb2(PO3)5, LiCs(PO3)2, et αLiK(PO3)2

The electrical conductivity of the crystallized polyphosphates Li₃Ba₂(PO₃)₇, LiPb₂(PO₃)₅, LiCs(PO₃)₂, and αLiK(PO₃)₂ has been determined at different temperatures by impedance spectroscopy. The conductivity, σ, spreads within a range of 1.59 × 10⁻⁸ to 1.79 × 10⁻⁷ S cm⁻¹ at 573 K, and from 1.71 × 10⁻⁵ to 9.86 × 10⁻⁴ S cm⁻¹ at 773 K. The transport should be assumed in the majority by the lithium ions with regard to the structural characteristics of these polyphosphates. The results are discussed and compared to the conductivity properties of other lithium ion conductors.     

Equilibrium diagram of KPO3–Y(PO3)3 system, chemical preparation and characterization of KY(PO3)4

Microdifferential thermal analysis (μ-DTA), X-ray diffraction (XRD) and infrared (IR) spectroscopy were used for the first time to investigate the liquidus and solidus relations in the KPO₃–Y(PO₃)₃ system. The only compound observed within the system was KY(PO₃)₄ melting incongruently at 1033 K. An eutectic appears at 13.5 mol% Y(PO₃)₃ at 935 K, the peritectic occurs at 1033 K and the phase transition for potassium polyphosphate KPO₃ was observed at 725 K. Three monoclinic allotropic phases of the single crystals were obtained. KY(PO₃)₄ polyphosphate has the P2₁ space group with lattice parameters: a=7.183(4) Å, b=8.351(6) Å, c=7.983(3) Å, β=91.75(3)° and Z=2 is isostructural with KNd(PO₃)₄. The second allotropic form of KY(PO₃)₄ belongs to the P2₁/n space group with lattice parameters: a=10.835(3) Å, b=9.003(2) Å, c=10.314(1) Å, β=106.09(7)° and Z=4 and is isostructural with TlNd(PO₃)₄. The IR absorption spectra of the two forms show a chain polyphosphates structure. The last modification of KYP₄O₁₂ crystallizes in the C2/c space group with lattice parameters: a=7.825(3) Å, b=12.537(4) Å, c=10.584(2) Å, β=110.22(7)° and Z=4 is isostructural with RbNdP₄O₁₂ and contains cyclic anions. The methods of chemical preparations, the determination of crystallographic data and IR spectra for these compounds are reported.     

Crystal structures and phase transitions of SrZr(PO4)2-BaZr(PO4)2 solid solutions

A complete series of solid solutions was prepared in the SrZr(PO₄)₂-BaZr(PO₄)₂ system and examined by conventional X-ray powder diffraction (XRPD). The crystals of Sr_xBa_1−xZr(PO₄)₂ with x?0.1 were isomorphous with yavapaiite (KFe(SO₄)₂, space group C2/m). The solid solution with 0.2?x?0.7 has been composed of a new phase, showing a superstructure along the a-axis (c-axis of the yavapaiite substructure). The crystals with 0.8?x?0.9 were composed of both the new phase and the triclinic phase, the latter being isostructural with SrZr(PO₄)₂ (x=1). The crystal structure of the new phase has been determined using direct methods, and it has been further refined by the Rietveld method. The crystal of Sr_0.7Ba_0.3Zr(PO₄)₂ (x=0.7) is monoclinic (space group P2/c, Z=4 and D_x/Mg m⁻³=3.73) with a=1.53370(8) nm, b=0.52991(3) nm, c=0.84132(4) nm, β=92.278(1)° and V=0.68321(6) nm³. Final reliability indices are R_wp=7.32%, R_p=5.60% and R_B=3.22%. The powder specimen was also examined by high-temperature XRPD and differential thermal analysis (DTA) to reveal the occurrence of two phase transitions during heating; the space group changed from P2/c to C2/m at ∼400 K, followed by the monoclinic-to-hexagonal (or trigonal) transition at 1060 K. The P2/c-to-C2/m transition has been, for the first time, described in the yavapaiite-type compounds.     

Ba3 (VO4)2-K2 Ba(MoO4)2 and Pb3 (VO4)2-K2 Pb(MoO4)2 systems

Phase equilibria in the Ba₃(VO₄)₂-K₂Ba(MoO₄)₂ and Pb3(VO₄)₂-K₂Pb(MoO₄)₂ systems have been investigated. In the first system, a continuous series of substitutional solid solutions with the palmierite structure is formed, and in the second one, the polymorphic transition in lead orthovanadate at 100°C restricts the extent of the palmierite-type solid solution to 10–100 mol % K₂Pb(MoO₄)₂. Original Russian Text ? V.D. Zhuravlev, Yu.A. Velikodnyi, A.S. Vinogradova-Zhabrova, A.P. Tyutyunnik, V.G. Zubkov, 2008, published in Zhurnal Neorganicheskoi Khimii, 2008, Vol. 53, No. 10, pp. 1746–1748.     

Topotactic insertion of lithium in the layered structure Li4VO(PO4)2: The tunnel structure Li5VO(PO4)2

A new V(III) lithium phosphate Li₅VO(PO₄)₂ has been synthesized by electrochemical insertion of lithium into Li₄VO(PO₄)₂. This phase, which crystallizes in the space group I4/mcm, exhibits a tunnel structure closely related to the layered structure of Li₄VO(PO₄)₂ and to the tunnel structure of VO(H₂PO₄)₂. The topotactic reactions that take place during lithium exchange and intercalation, starting from VO(H₂PO₄)₂ and going to the final phase Li₅VO(PO₄)₂ are explained on the basis of the flexible coordinations of V⁴⁺ and V³⁺ species. The electrochemical and magnetic properties of this new phase are also presented and explained on the basis of the structure dimensionality.     

Disorder in the crystal structure of NaNi4(PO4)3

NaNi₄(PO₄)₃ crystallizes in the space group Amam, a = 9.892(1), B = 14.842(2), and c = 6.3576(2) Å. For Z = 4, the calculated density is 3.862 g/cm³ (V = 933.3ų). The presence of several weak reflections (of the class 2k0 and 6k0) which should be systematically absent in this space group has been attributed to a partial disorder of one of the phosphate tetrahedra. Two half-occupied P(2) sites related by a mirror normal to the a axis result in a column of phosphate tetrahedra pointing either up or down in this direction. Nickel atoms occupy five- and six-coordinated sites while sodium is six-coordinated.     

Co3{CH3C(NH3)(PO3H)(PO3)}2 {CH3C(NH3)(PO3H)2}2(H2O)4·2H2O: A cobalt 1-aminoethylidenediphosphonate with a layer structure

This paper describes the structure and magnetic properties of a novel cobalt 1-aminoethylidenediphosphonate compound, namely Co₃{CH₃C(NH₃)(PO₃H)(PO₃)}₂{CH₃C(NH₃)(PO₃H)₂}₂(H₂O)₄·2H₂O (1). The structure contains a trimer unit of Co₃{CH₃C(NH₃)(PO₃H)(PO₃)}₂ in which two equivalent phosphonate ligands chelate and bridge the three cobalt ions. Each trimer unit is further linked to its four equivalent neighbors through corner-sharing of CoO₆ octahedra and CPO₃ tetrahedra, forming a two-dimensional layer in the bc-plane which contains 12-membered rings. These layers are connected to each other by extensive hydrogen bonds. Magnetic studies show that weak antiferromagnetic interactions are mediated between the cobalt ions. Crystal data for 1: monoclinic, space group C2/c, a=27.727(4), b=7.1091(11), , β=118.488(3), , Z=2.     

NASICON型Na4FeV(PO4)3的合成、晶体结构和电化学性能

采用高温熔盐法制备了NASICON型Na_4Fe V(PO_4)_3单晶。单晶X射线衍射数据分析表明,Na_4Fe V(PO_4)_3属于六方R3c空间群,单胞参数为a=b=0.878 17(4) nm,c=2.170 1(2) nm,Z=6,V=1.449 31(18) nm~3。该磷酸盐属于典型的NASICON结构,由PO_4四面体和Fe/VO_6八面体共顶点组成三维框架结构,提供多维的Na~+传输通道,2种不同类型Na~+位于框架的间隙。以Na_4Fe V(PO_4)_3/C粉末样品作为钠电池正极材料并以金属钠为对电极制备电池时,电化学测试结果表明其具有较高的容量。