Nataliya Yu. Strutynska

Rietveld refinement of AgCa10(PO4)7 from X-ray powder data.

Polycrystalline silver(I) decacalcium heptakis(orthophosphate), AgCa10(PO4)7, was obtained by solid-state reaction. It is isotopic with members of the series MCa10(PO4)7 (M = Li, Na, K and Cs), and is closely related to the structure of β-Ca3(PO4)2. The crystal structure of the title compound is built up from a framework of [CaO9] and two [CaO8] polyhedra, one [CaO6] octahedron (site symmetry 3.) and three PO4 tetrahedra (one with site symmetry 3.). The Ag+ cation is likewise located on a threefold rotation axis and resides in the cavities of the rigid [Ca10(PO4)7]− framework. It is surrounded by three O atoms in an almost regular triangular environment.

The triple pyrophosphate Cs3CaFe(P2O7)2.

The complex phosphate tricaesium calcium iron bis(diphosphate), Cs(3)CaFe(P(2)O(7))(2), has been prepared by the flux method. Isolated [FeO(5)] and [CaO(6)] polyhedra are linked by two types of P(2)O(7) groups into a three-dimensional framework. The latter is penetrated by hexagonal channels along the a axis where three Cs atoms are located. Calculations of caesium Voronoi-Dirichlet polyhedra give coordination schemes for the three Cs atoms as [8 + 3], [9 + 1] and [9 + 4]. The structure includes features of both two- and three-dimensional frameworks of caesium double pyrophosphates.

Chemical Interaction of Phosphates MII2P4O12 with Melted MICl or MINO3 (MI – Li, Na, K; MII – Mg, Co, Ni, Zn)

The interaction in the systems MII2P4O12-MICl (MINO3) (MI – Li, Na, K; MII – Mg, Co, Ni, Zn) was investigated in temperature range 1073-673 K. The conditions of formation phosphates: Li3PO4, MIMIIPO4 (MI – Na, K), Na4MII3(PO4)2P2O7, Na9Co3(PO4)5 have been established. Obtained crystalline phases have been investigated using X-ray powder diffraction, Diffuse reflectance, Raman and FTIR spectroscopy and scanning electron microscopy methods.

KNi(0.93)Fe(II)(0.07)Fe(III)(PO4)2: a new type of structure for a compound of composition M(I)M(II)M(III)(PO4)2.

The solid solution KNi(0.93)Fe(II)(0.07)Fe(III)(PO4)2 {potassium [nickel(II)/iron(II)] iron(III) bis(orthophosphate)} has been prepared by the flux method. The compound shows a new type of structure for a phosphate with the general composition M(I)M(II)M(III)(PO4)2. The framework is formed by [(Ni/Fe)O6] polyhedra [Fe site occupancy = 0.069 (14)] linked via shared oxygen vertices forming a cis-like parallel chain stretching along a and [FeO5] polyhedra (located on alternate sides of the chains) connected via two types of PO4 groups into a three-dimensional structure. The K atoms are disordered between two sites, denoted K1A and K1B, with occupancies of 0.930 (9) and 0.070 (9), respectively, and reside inside channels along the a axis. Calculations of the Voronoi-Dirichlet polyhedra of the K atoms give a coordination scheme for K1A of [9 + 3] and for K1B of [10 + 2]. The most remarkable feature of the structure is the splitting of the K-atom site and the population of the K1A and K1B positions due to substitution of Ni by Fe in the (Ni/Fe) position.

Rietveld refinement of whitlockite-related K0.8Ca9.8Fe0.2(PO4)7

The title compound, K0.8Ca9.8Fe0.2(PO4)7 (potassium decacalcium iron heptaphosphate), belongs to the whitlockite family. The structure is built up from several types of metal–oxygen polyhedra: two [CaO8], one [CaO7] and one [(Ca/Fe)O6] polyhedron with a mixed Ca/Fe occupancy in a 0.8:0.2 ratio, as well as three tetrahedral [PO4] units. Of the 18 sites in the asymmetric unit, the site with the mixed Ca/Fe occupation, the K site, one P and one O site are on special positions 6a with 3 symmetry, whereas all other sites are on general positions 18b. The linkage of metal–oxygen polyhedra and [PO4] tetrahedra via edges and corners results in formation of a three-dimensional framework with composition [Ca9.8Fe0.2(PO4)7]0.8−. The remaining K atoms (site-occupation factor = 0.8) are located in large closed cavities and are nine-coordinated by oxygen.

A novel In3O16 fragment in Cs3In3(PO4)4.

The double phosphate Cs(3)In(3)(PO(4))(4), prepared by a flux technique, features a fragment of composition In(3)O(16) formed by three corner-sharing InO(6) polyhedra. The central In atom resides on a twofold rotation axis, while the other two In atoms are on general positions. The O atoms in this fragment also belong to PO(4) tetrahedra, which link the structure into an overall three-dimensional anionic In-O-P network that is penetrated by tunnels running along c. Two independent Cs(+) cations reside inside the tunnels, one of which sits on a centre of inversion. In general, the organization of the framework is similar to that of K(3)In(3)(PO(4))(4), which also contains an In(3)O(16) fragment. However, in the latter case the unit consists of one InO(7) polyhedron and one InO(6) polyhedron sharing an edge, with a third InO(6) octahedron connected via a shared corner. Calculations of the Voronoi-Dirichlet polyhedra of the alkali metals give coordination schemes for Cs of [9+2] and [8+4] (1 symmetry), and for K of [8+1], [7+2] and [7+2]. This structural analysis shows that the coordination requirements of the alkali metals residing inside the tunnels cause the difference in the In(3)O(16) geometry.

NASICON-related Na3.4Mn0.4Fe1.6(PO4)3

The solid solution, sodium [iron(III)/manganese(II)] tris(orthophosphate), Na3.4Mn0.4Fe1.6(PO4)3, was obtained using a flux method. Its crystal structure is related to that of NASICON-type compounds. The [(Mn/Fe)2(PO4)3] framework is built up from an (Mn/Fe)O6 octahedron (site symmetry 3.), with a mixed Mn/Fe occupancy, and a PO4 tetrahedron (site symmetry .2). The Na+ cations are distributed over two partially occupied sites in the cavities of the framework. One Na+ cation (site symmetry -3.) is surrounded by six O atoms, whereas the other Na+ cation (site symmetry .2) is surrounded by eight O atoms.

Synthesis, characterization and electrical properties of glass-ceramic samples of M I x Na 4−x CoFe(PO 4 ) 3 (M I - Li, K) composition

The vitreous samples of M^I_xNa_4-xCoFe(PO₄)₃ (x = 0, 0.2 and 1.0, M^I - Li, K) composition were prepared by melt method. Formation of Nasicon-related crystalline samples was caused by the annealing at 600 °C. The cell parameters calculation showed that its evolution along two series agrees with the substitution of Na⁺ by smaller Li⁺ and bigger K⁺ cations. The electrical properties were investigated by the impedance method.

Synthesis, characterization and EPR investigation of γ-induced defects for nanoparticles of (M I , CO 3 )-containing (M I - Na, K) apatites

The results of a comparative study of amorphous (Na, CO₃)- and (K, CO₃)-containing apatites by TPM MS analysis, FTIR, XRD, SEM and EPR are presented. Annealing of amorphous apatite at temperatures below 400°C does not lead to changing of nanoparticle shape and size and an extent of its crystallinity. A significant difference in the formation of γ-induced defects in (Na, CO₃)- and (K,CO₃)-containing apatites was found.

Interaction in the systems M II 2 P 4 O 12 -M I Cl(M I NO 3 ) (M I - Li, Na, K; M II - Co, Ni)

The interaction in the systems M^II₂P₄O₁₂-M^ICl (M^INO₃) (M^I - Li, Na, K; M^II - Co, Ni) was investigated in temperature range 673-1073 K. Obtained crystalline phases have been investigated using X-ray powder diffraction, electronic, Raman and FTIR spectroscopy and scanning electron microscopy.