Insights into structure, morphology and conductivity of the earth-abundant NASICON phosphate, Na4MnFe(PO4)3.

Phosphate-based NASICON materials are an excellent candidate for both electrode and solid electrolyte materials in sodium-ion batteries (SIBs). The development of new NASICON materials with higher ionic and electronic conductivities based on low cost and abundant elements is necessary for advancement of SIBs. In this study, we report the structure, morphology and conductivity of the earth-abundant Mn/Fe-based NASICON phosphate Na4MnFe(PO4)3. Pure phase powders were synthesized by solution-assisted solid-state reaction, sol-gel and Pechini methods. From refined X-ray diffraction data, the prepared phosphate was found to crystallize in trigonal symmetry with space group R3̄c. The effect of synthesis method on microstructure and conductivity was investigated using scanning electron microscopy (SEM), atomic force microscopy (AFM) and impedance measurements. Smaller particle size and regular distribution of the powder was designed using a Pechini route. Impedance measurement showed a notable enhancement in conductivity, from 0.543 × 10-7 to 1.52 × 10-7 S cm-1 at 30 °C, when the powder synthesis method was altered from a solution-assisted solid-state reaction to the Pechini route, highlighting the remarkable effect of the synthesis method on conductivity.

A novel phosphate with CoII square planar coordination, BaCo0.5Fe(PO4)2: structural and magnetic features.

A novel phosphate containing barium, cobalt, and iron was synthesized in single-crystal and polycrystalline forms. Single crystal-based X-ray measurements revealed that it crystallizes in the monoclinic system with the P21/c space group. The structure is made up of linkages between FeO6 octahedra, CoO4 square planar units, CoO5 square pyramidal units, and PO4 tetrahedra through edges and/or vertices. The interconnection of these polyhedra leads to a three-dimensional framework with tunnels along the a-axis where the Ba2+ cations are located. The polycrystalline form was prepared via the sol-gel method and its XRD pattern was refined by the Le Bail method. Morphological and elemental mapping analyses of this phosphate were performed by scanning electron microscopy. In addition, infrared and Raman spectroscopy provided more insights into chemical bonding. The magnetic behavior was antiferromagnetic below TN ∼ 20 K. Optical measurements revealed a direct bandgap with an energy Eg of 2.83 eV.

Distrontium trimanganese(II) bis-(hydro-gen-phosphate) bis-(ortho-phosphate).

The title compound, Sr2Mn3(HPO4)2(PO4)2, was synthesized under hydro-thermal conditions. In the structure, one of two Mn atoms is located on an inversion centre, whereas all others atoms are located in general positions. The framework structure is built up from two types of MnO6 octa-hedra (one almost undistorted, one considerably distorted), one PO3OH and one PO4 tetra-hedron. The centrosymmetric MnO6 octa-hedron is linked to two other MnO6 octa-hedra by edge-sharing, forming infinite zigzag chains parallel to [010]. The PO3OH and PO4 tetra-hedra connect these chains through common vertices or edges, resulting in the formation of sheets parallel to (100). The Sr(2+) cation is located in the inter-layer space and is bonded to nine O atoms in form of a distorted polyhedron and enhances the cohesion of the layers. Additional stabilization is achieved by a strong inter-layer O-H⋯O hydrogen bond between the PO3OH and PO4 units. The structure of the title phosphate is isotypic to that of Pb2Mn3(HPO4)2(PO4)2.

A new mixed-valence lead(II) mangan-ese(II/III) phosphate(V): PbMn(II) 2Mn(III)(PO4)3.

The title compound, lead trimanganese tris(orthophosphate), has been synthesized by hydro-thermal methods. In this structure, only two O atoms are in general positions and all others atoms are in the special positions of the Imma space group. Indeed, the atoms in the Wyckoff positions are namely: Pb1 and P1 on 4e (mm2); Mn1 on 4b (2/m); Mn2 and P2 on 8g (2); O1 on 8h (m); O2 on 8i (m). The crystal structure can be viewed as a three-dimensional network of corner- and edge-sharing PO4 tetra-hedra and MnO6 octa-hedra, building two types of chains running along the b axis. The first is an infinite linear chain, formed by alternating Mn(III)O6 octa-hedra and PO4 tetra-hedra which share one vertex. The second chain is built up from two adjacent edge-sharing octa-hedra (Mn(II) 2O10 dimers) whose ends are linked to two PO4 tetra-hedra by a common edge. These chains are linked together by common vertices of polyhedra in such a way as to form porous layers parallel to (001). These sheets are bonded by the first linear chains, leading to the appearance of two types of tunnels, one propagating along the a axis and the other along b. The Pb(II) ions are located within the inter-sections of the tunnels with eight neighbouring O atoms in form of a trigonal prism that is capped by two O atoms on one side. The three-dimensional framework of this structure is compared with similar phosphates such as Ag2Co3(HPO4)(PO4)2 and Ag2Ni3(HPO4)(PO4)2.

A triclinic polymorph of dicadmium divanadate(V).

The title compound, Cd2V2O7, was obtained under hydro-thermal conditions. Different from the known monoclinic form, the new polymorph of Cd2V2O7 has triclinic symmetry and is isotypic with Ca2V2O7. The building units of the crystal structure are two Cd(2+) cations, with coordination numbers of six and seven, and two V atoms with a tetra-hedral and a significantly distorted trigonal-pyramidal coordination environment, respectively. Two VO5 pyramids share an edge and each pyramid is connected to one VO4 tetra-hedron via a corner atom, forming an isolated V4O14 (8-) anion. These anions are arranged in sheets parallel to (-211) and are linked through the Cd(2+) cations into a three-dimensional framework structure.

SrMn(II) 2Mn(III)(PO4)3.

The title compound, strontium trimanganese tris-(ortho-phosphate), was synthesized under hydro-thermal conditions. Its structure is isotypic to that of the lead analogue PbMn(II) 2Mn(III)(PO4)3. Two O atoms are in general positions, whereas all others atoms are in special positions. The Sr and one P atom exhibit mm2 symmetry, the Mn(II) atom 2/m symmetry, the Mn(III) atom and the other P atom .2. symmetry and two O atoms are located on mirror planes. The three-dimensional network of the crystal structure is made up of two types of chains running parallel to [010]. One chain is linear and is composed of alternating Mn(III)O6 octa-hedra and PO4 tetra-hedra sharing vertices; the other chain has a zigzag arrangement and is built up from two edge-sharing Mn(II)O6 octa-hedra connected to PO4 tetra-hedra by edges and vertices. The two types of chains are linked through PO4 tetra-hedra, leading to the formation of channels parallel to [100] and [010] in which the Sr(II) ions are located. They are surrounded by eight O atoms in the form of a slightly distorted bicapped trigonal prism.

BaMn(II) 2Mn(III)(PO4)3.

The title compound, barium trimanganese tris-(ortho-phosphate), was synthesized hydro-thermally. Its structure is isotypic with the lead and strontium analogues AMn(II) 2Mn(III)(PO4)3 (A = Pb, Sr). Except for two O atoms on general positions, all atoms are located on special positions. The Ba and one P atom exhibit mm2 symmetry, the Mn(II) atom 2/m symmetry, the Mn(III) atom and the other P atom .2. symmetry and two O atoms are located on mirror planes. The crystal structure contains two types of chains running parallel to [010]. One chain is linear and is composed of alternating Mn(III)O6 octa-hedra and PO4 tetra-hedra sharing vertices; the other chain has a zigzag arrangement and is built up from two edge-sharing Mn(II)O6 octa-hedra connected to PO4 tetra-hedra by edges and vertices. The two types of chains are linked through PO4 tetra-hedra into an open three-dimensional framework which contains channels parallel to [100] and [010] in which the Ba(II) ions are located. The alkaline earth cation is surrounded by eight O atoms in the form of a slightly distorted bicapped trigonal prism.

Crystal structure of barium dinickel(II) iron(III) tris-[orthophosphate(V)], BaNi2Fe(PO4)3.

The orthophosphate BaNi2Fe(PO4)3 has been synthesized by a solid-state reaction route and characterized by single-crystal X-ray diffraction and energy-dispersive X-ray spectroscopy. The crystal structure comprises (100) sheets made up of [Ni2O10] dimers that are linked to two PO4 tetra-hedra via common edges and vertices and of linear infinite [010] chains of corner-sharing [FeO6] octa-hedra and [PO4] tetra-hedra. The linkage of the sheets and chains into a framework is accomplished through common vertices of PO4 tetra-hedra and [FeO6] octa-hedra. The framework is perforated by channels in which positionally disordered Ba2+ cations are located.

Crystal structure reinvestigation and spectroscopic analysis of tricadmium orthophosphate.

Single crystals of tricadmium orthophosphate, Cd3(PO4)2, have been synthesized successfully by the hydro-thermal route, while its powder form was obtained by a solid-solid process. The corresponding crystal structure was determined using X-ray diffraction data in the monoclinic space group P21/n. The crystal structure consists of Cd2O8 or Cd2O10 dimers linked together by PO4 tetra-hedra through sharing vertices or edges. Scanning electron microscopy (SEM) was used to investigate the morphology and to confirm the chemical composition of the synthesized powder. Infrared analysis corroborates the presence of isolated phosphate tetra-hedrons in the structure. UV-Visible studies showed an absorbance peak at 289 nm and a band gap energy of 3.85 eV, as determined by the Kubelka-Munk model.

Dicobalt(II) lead(II) hydrogenphos-phate(V) phos-phate(V) hydroxide monohydrate.

The title compound, Co(2)Pb(HPO(4))(PO(4))OH·H(2)O, which was synthesized under hydro-thermal conditions, crystallizes in a new structure type. Except for two O atoms in general positions and two Co atoms on centres of symmetry, all other atoms in the asymmetric unit (1 Pb, 2 Co, 2 P, 8 O and 4 H) are located on mirror planes. The structure is built up from two infinite linear chains, viz.(1) (∞)[CoO(2/1)(H(2)O)(2/2)O(2/2)] and (1) (∞)[CoO(2/1)(OH)(2/2)O(2/2)], of edge-sharing CoO(6) octa-hedra running along [010]. Adjacent chains are linked to each other through PO(4) and PO(3)(OH) tetra-hedra, leading to the formation of layers parallel to (100). The three-dimensional framework is formed by stacking along [100] of adjacent layers that are held together by distorted PbO(8) polyhedra. Hydrogen bonds of the type O-H⋯O involving the water mol-ecule are very strong, while those O atoms involving the OH groups form weak bifurcated and trifurcated hydrogen bonds.

Dilead(II) trimanganese(II) bis(hydrogenphosphate) bis(phosphate).

The title compound, Pb(2)Mn(3)(HPO(4))(2)(PO(4))(2), was synthesized by a hydro-thermal method. All atoms are in general positions except for one Mn atom which is located on an inversion center. The framework of the structure is built up from PO(4) tetra-hedra and two types of MnO(6) octa-hedra, one almost ideal and the other very distorted with one very long Mn-O bond [2.610 (4) Šcompared an average of 2.161 Šfor the other bonds]. The centrosymetric octa-hedron is linked to two distorted MnO(6) octa-hedra by an edge common, forming infinite zigzag Mn(3)O(14) chains running along the b axis. Adjacent chains are linked by PO(4) and PO(3)(OH) tetra-hedra through vertices or by edge sharing, forming sheets perpendicular to [100]. The Pb(2+) cations are sandwiched between the layers and ensure the cohesion of the crystal structure. O-H⋯O hydrogen bonding between the layers is also observed.

Crystal growth, structure elucidation and CHARDI/BVS investigations of ß-KCoFe(PO4)2.

Single crystals of ß-KCoFe(PO4)2, potassium cobalt(II) iron(III) bis-(ortho-phosphate), were grown from the melt under atmospheric conditions. This phosphate crystallizes isotypically with KZnFe(PO4)2 in space group C2/c, adopting a zeolite-ABW type of structure. The structure of the present phosphate is distinguished by an occupational disorder of the two transition-metal sites with ratios Fe:Co of 0.5725:0.4275 for the first and 0.4275:0.5725 for the second site. In the crystal structure, PO4 and (Co,Fe)O4 tetra-hedra are linked through vertices to form elliptical rings with the sequence DDDDUUUU of up (U) and down (D) pointing vertices. Each eight-membered ring is surrounded by four other rings of the same type, delimiting inter-stices with rectangular shape. This arrangement leads to the formation of [(Co/Fe)(PO4)]- ∞ sheets parallel to (001). Stacking of the sheets into a three-dimensional framework results in the formation of two types of channels. The first one is occupied by potassium cations, whereas the second one remains vacant. Calculations of bond-valence sums and charge distribution were used to confirm the structure model.

Disilver(I) trinickel(II) hydrogenphos-phate bis-(phosphate), Ag(2)Ni(3)(HPO(4))(PO(4))(2).

The title compound, Ag(2)Ni(3)(HPO(4))(PO(4))(2), has been synthesized by the hydro-thermal method. Its structure is formed by two types of chains running along the b axis. The first chain results from a linear and continuous succession of NiO(6) octa-hedra linked to PO(4) tetra-hedra by a common vertex. The second chain is built up from two adjacent edge-sharing octa-hedra (dimers) whose ends are linked to two PO(4) tetra-hedra by a common edge. Those two types of chains are linked together by the phosphate groups to form polyhedral sheets parallel to the (001) plane. The three-dimensional framework delimits two types of hexa-gonal tunnels parallel to the a-axis direction, at (x, 1/2, 0) and (x, 0, 1/2), where the Ag atoms are located. Each silver cation is surrounded by eight O atoms. The same Ag(+) coordination is found in other phosphates with the alluaudite structure, for example, AgMn(3)(PO(4))(HPO(4))(2). Moreover, O-H⋯O hydrogen bonds link three PO(4) tetra-hedra so as to build a three-dimensional network.

Disilver(I) tricobalt(II) hydrogenphos-phate bis-(phosphate), Ag(2)Co(3)(HPO(4))(PO(4))(2).

Ag(2)Co(3)(HPO(4))(PO(4))(2) contains CoO(6) octa-hedra and phosphate groups linked to form a three-dimensional network defining tunnels parallel to the a axis that are occupied by Ag(+) ions.

Thorium divanadate dihydrate, Th(V(2)O(7))(H(2)O)(2).

The title compound, Th(V(2)O(7))(H(2)O)(2), was synthesized by a hydro-thermal reaction. The crystal structure consists of ThO(7)(OH(2))(2) tricapped trigonal prisms that share edges, forming [ThO(5)(OH(2))(2)](n) chains along [010]. The edge-sharing ThO(7)(OH(2))(2) polyhedra share one edge and five vertices with the V(2)O(7) divanadate anions having a nearly ecliptic conformation parallel to [001]. This results in an open framework with the water mol-ecules located in channels. O-H⋯O hydrogen bonding between water molecules and framework O atoms is observed. Bond-valence-sum calculations are in good agreement with the chemical formula of the title compound.

Heptamagnesium bis-(phosphate) tetra-kis-(hydrogen phosphate) with strong hydrogen bonds: Mg(7)(PO(4))(2)(HPO(4))(4).

The title compound, Mg(7)(PO(4))(2)(HPO(4))(4), was synthesized by the hydro-thermal method. The structure is based on a framework of edge- and corner-sharing MgO(6) and MgO(4)(OH)(2) octa-hedra, an MgO(5) polyhedron, PO(4) and PO(3)(OH) tetra-hedra. All atoms are in general positions except for one Mg atom, which is located on a crystallographic inversion centre. The OH groups, bridging Mg-(OH)-P, are involved in strong hydrogen bonds. Compounds with the general formula M(7)(PO(4))(2)(HPO(4))(4) (M = Mg, Mn, Fe and Co) are all isostructural with their homologue arsenate Mg(7)(AsO(4))(2)(HAsO(4))(4).

Dicobalt copper bis-[orthophosphate(V)] monohydrate, Co(2.39)Cu(0.61)(PO(4))(2)·H(2)O.

In an attempt to hydro-thermally synthesize a phase with composition Co(2)Cu(PO(4))(2)·H(2)O, we obtained the title compound, Co(2.39)Cu(0.61)(PO(4))(2)·H(2)O instead. Chemical analysis confirmed the presence of copper in the crystal. The crystal structure of the title compound can be described as a three- dimensional network constructed from the stacking of two types of layers extending parallel to (010). These layers are made up from more or less deformed polyhedra: CoO(6) octa-hedra, (Cu/Co)O(5) square pyramids and PO(4) tetra-hedra. The first layer is formed by pairs of edge-sharing (Cu/Co)O(5) square pyramids linked via a common edge of each end of the (Cu/Co)(2)O(8) dimer to PO(4) tetra-hedra. The second layer is undulating and is built up from edge-sharing CoO(6) octa-hedra. The linkage between the two layers is accomplished by PO(4) tetra-hedra. The presence of water mol-ecules in the CoO(4)(H(2)O)(2) octa-hedron also contributes to the cohesion of the layers through O-H⋯O hydrogen bonding.

A one-dimensional inorganic-organic hybrid compound: catena-poly[ethyl-enediammonium [indate(III)-di-µ-hydrogenphosphato(V)-µ-hydroxido] monohydrate].

The title compound, (C(2)H(10)N(2))[In(HPO(4))(2)(OH)]·H(2)O, was synthesized under hydro-thermal conditions. The structure of this hybrid compound consists of isolated inorganic chains with composition (∞)[In(HPO(4))(4/2)(OH)(2/2)] running along [010]. The coordination of the In(III) atom is distorted octa-hedral. The ethyl-enediammonium cation and the disordered water mol-ecule (site-occupation factors = 0.7:0.3) ensure the cohesion of the structure via N-H⋯O and O-H⋯O hydrogen bonds.

The γ-polymorph of AgZnPO(4) with an ABW zeolite-type framework topology.

The γ-polymorph of the title compound, silver zinc orthophos-phate, was synthesized under hydro-thermal conditions. The structure consists of ZnO(4), PO(4) and AgO(4) units. The coord-ination spheres of Zn(II) and P(V) are tetra-hedral, whereas the Ag(I) atom is considerably distorted from a tetra-hedral coordination. Each O atom is linked to each of the three cations. An elliptic eight-membered ring system is formed by corner-sharing of alternating PO(4) and ZnO(4) tetra-hedra, leading to a framework with an ABW-type zeolite structure. The framework encloses channels running parallel to [100] in which the Ag cations are located, with Ag⋯Ag contacts of 3.099 (3) Å. This short distance results from d(10)⋯d(10) inter-actions, which play a substantial role in the crystal packing. The structure of γ-AgZnPO(4) is distinct from the two other polymorphs α-AgZnPO(4) and ß-AgZnPO(4), but is isotypic with NaZnPO(4)-ABW, NaCoPO(4)-ABW and NH(4)CoPO(4)-ABW.

Poly[ethyl-enediammonium [tris-[µ(3)-hydrogenphosphato(2-)]dicadmium] monohydrate].

The title compound, {(C(2)H(10)N(2))[Cd(2)(HPO(4))(3)]·H(2)O}(n), was synthesized under hydro-thermal conditions. The structure of this hybrid compound consists of CdO(6), CdO(5) and PO(4) polyhedra arranged so as to build an anionic inorganic layer, namely [Cd(2)(HPO(4))(3)](2-), parallel to the ab plane. The edge-sharing CdO(6) octa-hedra form infinite chains running along the a axis and are linked by CdO(5) and PO(4) polyhedra. The ethyl-ene-diammonium cation and the water mol-ecule are located between two adjacent inorganic layers and ensure the cohesion of the structure via N-H⋯O and O-H⋯O hydrogen bonds.