Igor V. Zatovsky

NASICON-type Na3V2(PO4)3

Single crystals of the title compound, trisodium divanadium(III) tris(orthophosphate), were grown from a self-flux in the system Na4P2O7–NaVP2O7. Na3V2(PO4)3 belongs to the family of NASICON-related structures and is built up from isolated [VO6] octahedra (3. symmetry) and [PO4] tetrahedra (.2 symmetry) interlinked via corners to establish the framework anion [V2(PO4)3]3−. The two independent Na+ cations are partially occupied [site-occupancy factors = 0.805 (18) and 0.731 (7)] and are located in channels with two different oxygen environments, viz sixfold coordination for the first (. symmetry) and eightfold for the second (.2 symmetry) Na+ cation.

Equilibrium langbeinite-related phosphates Cs1 + xLnxZr2 − x(PO4)3 (Ln = Sm–Lu) in the melted systems Cs2O–P2O5–LnF3–ZrF4

Nine novel phosphates, based upon a combination of caesium, zirconium and lanthanide ions, were obtained from fluoride-containing fluxes using high-temperature crystallization. The structures of Cs(1.80)Eu(0.80)Zr(1.20)(PO(4))(3) (CsEuZrP), Cs(1.79)Gd(0.79)Zr(1.21)(PO(4))(3) (CsGdZrP), Cs(1.87)Tb(0.87)Zr(1.13)(PO(4))(3) (CsTbZrP), Cs(1.67)Dy(0.67)Zr(1.33)(PO(4))(3) (CsDyZrP), Cs(1.75)Ho(0.75)Zr(1.25)(PO(4))(3) (CsHoZrP), Cs(1.78)Er(0.78)Zr(1.22)(PO(4))(3) (CsErZrP), Cs(1.70)Tm(0.70)Zr(1.30)(PO(4))(3) (CsTmZrP), Cs(1.52)Yb(0.52)Zr(1.48)(PO(4))(3) (CsYbZrP) and Cs(1.63)Lu(0.63)Zr(1.37)(PO(4))(3) (CsLuZrP) were solved using single-crystal X-ray diffraction. All compounds are isostructural to the mineral langbeinite (cubic system, space group P2(1)3). Their framework structures originate from the cross-linking of metal octahedra [MO(6)] (M = Zr, Ln) by phosphate tetrahedra. Cs(+) cations are located in the closed cavities of the framework and preferentially occupy one of the two available sites. The principles of crystallization of the equilibrium langbeinite-related phosphates in the fluxes of the system Cs(2)O-P(2)O(5)-LnF(3)-ZrF(4) (Ln = La-Nd, Sm-Lu) are discussed based on their crystal structures.

Phase formation of complex phosphate K4Ti3Ni(PO)4 in K2O-P2O5-TiO2-NiO melt solutions

The principles of complex phosphate crystallization in K2O-P2O5-TiO2-NiO solution melts are studied for the ratios K/P = 0.7−1.4, Ti/P = 0.15, and Ni/Ti = 0.1−2.0. The phase-formation field and parameters are determined for a new complex phosphate K4Ti3Ni(PO4)6, which is isostructural to langbeinite. A single-crystal X-ray diffraction experiments is carried out for this phosphate (space group P213, a = 9.8247(10) Å).

Electronic Structure and Luminescence Spectroscopy of M'Bi(MoO4)2 (M' = Li, Na, K), LiY(MoO4)2 and NaFe(MoO4)2 Molybdates

The mechanisms of intrinsic luminescence in the set of molybdate crystals of MIMIII(MoO4)2 (MI = Li, Na, K; MIII =Bi, Y, Fe) type are revealed in complex experimental and theoretical studies. The luminescence spectroscopy under vacuum ultraviolet (VUV) synchrotron excitations is applied together with the electronic structure calculations carried out by the FLAPW method. The energy gaps (Eg) values of the crystals are determined in simultaneous analysis of diffuse reflectance and luminescence excitation spectra. It is found that the molybdate groups MoO42- play a dominant role in the processes of intrinsic luminescence in studied molybdate compounds

K2Ho(PO4)(WO4)

A new compound, dipotassium holmium(III) phosphate(V) tungstate(VI), K2Ho(PO4)(WO4), has been obtained during investigation of the K2O–P2O5–WO3–HoF3 phase system using the flux technique. The compound is isotypic with K2Bi(PO4)(WO4). Its framework structure consists of flat ∞ 2[HoPO4] layers parallel to (100) that are made up of ∞ 1[HoO8] zigzag chains interlinked via slightly distorted PO4 tetrahedra. WO4 tetrahedra are attached above and below these layers, leaving space for the K+ counter-cations. The HoO8, PO4 and WO4 units exhibit 2 symmetry.

A disordered cerium(IV) phosphate with a tunnel structure, K4CeZr(PO4)4

Tetrapotassium cerium(IV) zirconium tetrakis(monophosphate) crystallizes in the tetragonal system (space group I4(1)/amd). A complex disorder in K4CeZr(PO4)4 involves the mixing of Ce and Zr atoms on a single site with -4m2 symmetry and the splitting of P- and O-atom positions, equivalent to a rotation of the phosphate groups, to yield eight- and sixfold coordination environments around Ce and Zr, respectively. The K atoms are located in tunnels running parallel to the a and b axes.

K2MIII2(MVIO4)(PO4)2 (MIII = Fe, Sc; MVI = Mo, W), Novel Members of the Lagbeinite-Related Family: Synthesis, Structure, and Magnetic Properties

The possibility of PO(4)(3-) for MoO(4)(2-) partial substitution in the langbeinite framework has been studied by exploration of the K-Fe(Sc)-Mo(W)-P-O systems using the high-temperature solution method. It was shown that 1/3PO(4)(3-) for MoO(4)(2-) substitution leads to formation of three novel compounds K(2)Fe(MoO(4))(PO(4))(2), K(2)Sc(MoO(4))(PO(4))(2), and K(2)Sc(WO(4))(PO(4))(2) with slightly increased lattice parameters and significant distortion of the anion tetrahedra without structure changes. In contrast, the antiferromagnetic structure is modified by substitution in the low-temperature region. The structural peculiarities are discussed in light of bond-valence sums calculations.

Structure of Biocompatible Coatings Produced from Hydroxyapatite Nanoparticles by Detonation Spraying.

Detonation-produced hydroxyapatite coatings were studied by scanning electron microscopy (SEM), X-ray powder diffraction (XRD), Raman spectroscopy, and electron paramagnetic resonance (EPR) spectroscopy. The source material for detonation spraying was a B-type carbonated hydroxyapatite powder. The coatings consisted of tetracalcium phosphate and apatite. The ratio depended slightly on the degree of crystallinity of the initial powder and processing parameters of the coating preparation. The tetracalcium phosphate phase was homogeneous; the apatite phase contained defects localized on the sixfold axis and consisted of hydroxyapatite and oxyapatite. Technological factors contributing to the transformation of hydroxyapatite powder structure during coating formation by detonation spraying are discussed.

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.

Rietveld refinement of langbeinite-type K2YHf(PO4)3

Potassium yttrium hafnium tris(orthophosphate) belongs to the langbeinite-family and is built up from [MO6] octahedra [in which the positions of the two independent M sites are mutually occupied by Y and Hf in a 0.605 (10):0.395 (10) ratio] and [PO4] tetrahedra connected via vertices into a three-dimensional framework. This framework is penetrated by large closed cavities in which the two independent K atoms are located; one of the K atoms is nine-coordinated and the other is 12-coordinated by surrounding O atoms. The K, Y and Hf atoms lie on threefold rotation axes, whereas the P and O atoms are located in general positions.