Nikolay S. Slobodyanik

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).

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.

Crystallization from Na2O-P2O5-Fe2O3-MIIO (MII = Mg, Ni) melts and the structure of Na4MgFe(PO4)3

We have studied general trends of phosphate crystallization from Na2O-P2O5-Fe2O3-MIIO (MII = Mg, Ni) high-temperature solutions at Na/P = 1.0−1.4, MII/Fe = 1.0, and Fe/P = 0.15 or 0.3, and identified the stability regions of the phosphates Na4MIIFe(PO4)3 (MII = Mg, Ni), NaFeP2O7, and Na2NiP2O7. The synthesized compounds have been characterized by X-ray powder diffraction and infrared spectroscopy. The structure of Na4MgFe(PO4)3 (sp. gr.

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

R\bar 3c

Cs2Bi(PO4)(WO4)

, a = 8.83954(13) Å, c = 21.4683(4) Å) has been determined by Rietveld powder diffraction analysis.

Polyanionic identity of Ca2Zn2(V3O10)(VO4) photocatalyst manifested by X-ray powder diffraction and periodic boundary density functional theory calculations

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.