Crystal structure of a sodium, zinc and iron(III)-based non-stoichiometric phosphate with an alluaudite-like structure: Na1.67Zn1.67Fe1.33(PO4)3

Synthesis, crystal structure determination of a novel phosphate Ag1.64Zn1.64Fe1.36(PO4)3 with an alluaudite-like structure

Single crystals of Ag1.64Zn1.64Fe1.36(PO4)3 [silver zinc iron phosphate (1.64/1.64/1.36/3)] have been synthesized by a conventional solid-state reaction and structurally characterized by single-crystal X-ray diffraction. The title compound crystallizes with an alluaudite-like structure. All atoms of the structure are in general positions except for four, which reside on special positions of the space group, C2/c. The Ag+ cations reside at full occupancy on inversion centre sites and at partial occupancy (64%) on a twofold rotation axis. In this structure, the unique Fe3+ ion with one of the two Zn2+ cations are substitutionally disordered on the same general position (Wyckoff site 8f), with a respective ratio of 0.68/0.32 (occupancies were fixed so as to ensure electrical neutrality for the whole structure). The remaining O and P atoms are located in general positions. The three-dimensional framework of this structure consists of kinked chains of edge-sharing octa-hedra stacked parallel to [10]. These chains are built up by a succession of [MO6] (M = Zn/Fe or Zn) units. Adjacent chains are connected by the PO4 anions, forming sheets oriented perpendicular to [010]. These inter-connected sheets generate two types of channels parallel to the c axis, in which the Ag+ cations are located. The validity and adequacy of the proposed structural model of Ag1.64Zn1.64Fe1.36(PO4)3 was established by means of bond-valence-sum (BVS) and charge-distribution (CHARDI) analysis tools.

Crystal structure of disilver(I) dizinc(II) iron(III) tris-(orthovanadate) with an alluaudite-type structure

The title compound, Ag2Zn2Fe(VO4)3, has been synthesized by solid-state reactions and belongs to the alluaudite structure family. In the crystal structure, four sites are positioned at special positions. One silver site is located on an inversion centre (Wyckoff position 4b), and an additional silver site, as well as one zinc and one vanadium site, on twofold rotation axes (4e). One site on a general position is statistically occupied by FeIII and ZnII cations that are octa-hedrally surrounded by O atoms. The three-dimensional framework structure of the title vanadate results from [(Zn,Fe)2O10] units of edge-sharing [(Zn,Fe)O6] octa-hedra that alternate with [ZnO6] octa-hedra so as to form infinite chains parallel to [10]. These chains are linked through VO4 tetra-hedra by sharing vertices, giving rise to layers extending parallel to (010). Such layers are shared by common vanadate tetra-hedra. The resulting three-dimensional framework delimits two types of channels parallel to [001] in which the silver sites are located with four- and sixfold coordination by oxygen.

Crystal structure of a silver-, cobalt- and iron-based phosphate with an alluaudite-like structure: Ag1.655Co1.64Fe1.36(PO4)3

The new silver-, cobalt- and iron-based phosphate, silver cobalt iron tris(ortho-phosphate), Ag1.655Co1.64Fe1.36(PO4)3, was synthesized by solid-state reactions. Its structure is isotypic to that of Na2Co2Fe(PO4)3, and belongs to the alluaudite family, with a partial cationic disorder, the AgI atoms being located on an inversion centre and twofold rotation axis sites (Wyckoff positions 4a and 4e), with partial occupancies of 0.885 (2) and 0.7688 (19), respectively. One of the two P atoms in the asymmetric unit completely fills one 4e site while the Co and Fe atoms fill another 4e site, with partial occupancies of 0.86 (5) and 0.14 (5), respectively. The remaining Co2+ and Fe3+ cations are distributed on a general position, 8f, in a 0.39 (4):0.61 (4) ratio. All O atoms and the other P atoms are in general positions. The structure is built up from zigzag chains of edge-sharing [MO6] (M = Fe/Co) octa-hedra stacked parallel to [101]. These chains are linked together through PO4 tetra-hedra, forming polyhedral sheets perpendicular to [010]. The resulting framework displays two types of channels running along [001], in which the AgI atoms (coordination number eight) are located.

Crystal structures of two alkaline earth (M = Ba and Sr) dimanganese(II) iron(III) tris-(orthophosphates)

Two new orthophosphates, BaMn2Fe(PO4)3 [barium dimanganese(II) iron(III) tris-(orthophosphate)] and SrMn2Fe(PO4)3 [strontium dimanganese(II) iron(III) tris-(orthophosphate)], were synthesized by solid-state reactions. They are isotypic and crystallize in the ortho-rhom-bic system with space group type Pbcn. Their crystal structures comprise infinite zigzag chains of edge-sharing FeO6 octa-hedra (point group symmetry .2.) and Mn2O10 double octa-hedra running parallel to [001], linked by two types of PO4 tetra-hedra. The so-formed three-dimensional framework delineates channels running along [001], in which the alkaline earth cations (site symmetry .2.) are located within a neighbourhood of eight O atoms.

Synthesis and crystal structure of calcium dizinc iron(III) tris-(orthophosphate), CaZn2Fe(PO4)3

Single crystals of the title compound, CaZn2Fe(PO4)3, were synthesized by conventional solid-state reaction. In the asymmetric unit, all atoms are located in fully occupied general positions of the P21/c space group. The zinc atoms are located on two crystallographically independent sites with tetra-hedral and distorted triangular-based bipyramidal geometries. Two edge-sharing triangular bipyramidal ZnO5 units form a dimer, which is linked to slightly deformed FeO6 octa-hedra via a common edge. The resulting chains are inter-connected through PO4 tetra-hedra to form a layer perpendicular to the b axis. Moreover, the remaining PO4 and ZnO4 tetra-hedra are linked together through common vertices to form tapes parallel to the c axis and surrounding a chain of Ca2+ cations to build a sheet, also perpendicular to the b axis. The stacking of the two layers along the b axis leads to the resulting three-dimensional framework, which defines channels in which the Ca2+ cations are located, each cation being coordinated by seven oxygen atoms.

Crystal structure of strontium dicobalt iron(III) tris-(orthophosphate): SrCo2Fe(PO4)3

The title compound, SrCo2Fe(PO4)3, has been synthesized by a solid-state reaction. It crystallizes with the α-CrPO4 type structure. In this structure, all atoms are on special positions of the Imma space group, except for two O atoms which are located on general positions. The three-dimensional network in the crystal structure is made up of two types of layers stacked normal to (100). The first layer is built from two edge-sharing CoO6 octa-hedra, leading to the formation of Co2O10 dimers that are connected to two PO4 tetra-hedra by a common edge and corners. The second layer results from apex-sharing FeO6 octa-hedra and PO4 tetra-hedra, which form linear chains alternating with a zigzag chain of Sr(II) cations. These layers are linked together by common vertices of PO4 tetra-hedra and FeO6 octa-hedra to form an open three-dimensional framework that delimits two types of channels parallel to [100] and [010] where the Sr(II) cations are located. Each Sr(II) cation is surrounded by eight O atoms.

The alluaudite-type crystal structures of Na2(Fe/Co)2Co(VO4)3 and Ag2(Fe/Co)2Co(VO4)3

Single crystals of the title compounds, disodium di(cobalt/iron) cobalt tris-(orthovanadate), Na2(Fe/Co)2Co(VO4)3, and disilver di(cobalt/iron) cobalt tris-(orthovanadate), Ag2(Fe/Co)2Co(VO4)3, were grown from a melt consisting of stoichiometric mixtures of three metallic cation precursors and vanadium pentoxide. The difficulty to distinguish between cobalt and iron by using X-ray diffraction alone forced us to explore several models, assuming an oxidation state of +II for Co and +III for Fe and a partial cationic disorder in the Wyckoff site 8f containing a mixture of Co and Fe with a statistical distribution for the Na compound and an occupancy ratio of 0.4875:0.5125 (Co:Fe) for the Ag compound. The alluaudite-type structure is made up from [10-1] chains of [(Co,Fe)2O10] double octa-hedra linked by highly distorted [CoO6] octa-hedra via a common edge. The chains are linked through VO4 tetra-hedra, forming polyhedral sheets perpendicular to [010]. The stacking of the sheets defines two types of channels parallel to [001] where the Na(+) cations (both with full occupancy) or Ag(+) cations (one with occupancy 0.97) are located.

Crystal structure of (Na0.70)(Na0.70,Mn0.30)(Fe(3+),Fe(2+))2Fe(2+)(VO4)3, a sodium-, iron- and manganese-based vanadate with the alluaudite-type structure

The title compound, sodium (sodium,manganese) triiron(II,III) tris[vana-date(V)], (Na0.70)(Na0.70,Mn0.30)(Fe(3+),Fe(2+))2Fe(2+)(VO4)3, was prepared by solid-state reactions. It crystallizes in an alluaudite-like structure, characterized by a partial cationic disorder. In the structure, four of the 12 sites in the asymmetric unit are located on special positions, three on a twofold rotation axis (Wyckoff position 4e) and one on an inversion centre (4b). Two sites on the twofold rotation axis are entirely filled by Fe(2+) and V(5+), whereas the third site has a partial occupancy of 70% by Na(+). The site on the inversion centre is occupied by Na(+) and Mn(2+) cations in a 0.7:0.3 ratio. The remaining Fe(2+) and Fe(3+) atoms are statistically distributed on a general position. The three-dimensional framework of this structure is made up of kinked chains of edge-sharing [FeO6] octa-hedra stacked parallel to [10-1]. These chains are held together by VO4 tetra-hedral groups, forming polyhedral sheets perpendicular to [010]. Within this framework, two types of channels extending along [001] are present. One is occupied by (Na(+)/Mn(2+)) while the second is partially occupied by Na(+). The mixed site containing (Na(+)/Mn(2+)) has an octa-hedral coordination sphere, while the Na(+) cations in the second channel are coordinated by eight O atoms.

Crystal structure of strontium dinickel iron orthophosphate

The title compound, SrNi2Fe(PO4)3, synthesized by solid-state reaction, crystallizes in an ordered variant of the α-CrPO4 structure. In the asymmetric unit, two O atoms are in general positions, whereas all others atoms are in special positions of the space group Imma: the Sr cation and one P atom occupy the Wyckoff position 4e (mm2), Fe is on 4b (2/m), Ni and the other P atom are on 8g (2), one O atom is on 8h (m) and the other on 8i (m). The three-dimensional framework of the crystal structure is built up by [PO4] tetra-hedra, [FeO6] octa-hedra and [Ni2O10] dimers of edge-sharing octa-hedra, linked through common corners or edges. This structure comprises two types of layers stacked alternately along the [100] direction. The first layer is formed by edge-sharing octa-hedra ([Ni2O10] dimer) linked to [PO4] tetra-hedra via common edges while the second layer is built up from a strontium row followed by infinite chains of alternating [PO4] tetra-hedra and FeO6 octa-hedra sharing apices. The layers are held together through vertices of [PO4] tetra-hedra and [FeO6] octa-hedra, leading to the appearance of two types of tunnels parallel to the a- and b-axis directions in which the Sr cations are located. Each Sr cation is surrounded by eight O atoms.

Crystal structure of alluaudite-type NaMg3(HPO4)2(PO4)

The title compound, sodium trimagnesium bis-(hydrogen phosphate) phosphate, was obtained under hydro-thermal conditions. In the crystal, two types of [MgO6] octa-hedra, one with point group symmetry 2, share edges to build chains extending parallel to [10-1]. These chains are linked together by two kinds of phosphate tetra-hedra, HPO4 and PO4, the latter with point group symmetry 2. The three-dimensional framework delimits two different types of channels extending along [001]. One channel hosts the Na(+) cations (site symmetry 2) surrounded by eight O atoms, with Na-O bond lengths varying between 2.2974 (13) and 2.922 (2) Å. The OH group of the HPO4 tetra-hedron points into the other type of channel and exhibits a strong hydrogen bond to an O atom of the PO4 tetra-hedron on the opposite side.