V. S. Kurazhkovskaya

Synthesis and crystal chemical characteristics of the structure of M0.5Zr2(PO4)3 phosphates

Double phosphates of zirconium and metals with an oxidation degree of +2 of the composition M0.5Zr2(PO4)3 (M = Mg, Ca, Mn, Co, Ni, Cu, Zn, Sr, Cd, and Ba) are synthesized and characterized by X-ray diffraction methods and IR spectroscopy. The crystal structures of all the compounds are based on three-dimensional frameworks of corner-sharing PO4-tetrahedra and ZrO6-octahedra. Phosphates with large Cd2+, Ca2+, Sr2+, and Ba2+ cations octahedrally coordinated with oxygen atoms form rhombohedral structures (space group R3), whereas phosphates with small tetrahedrally coordinated Mg2+, Ni2+, Cu2+, Co2+, Zn 2+, and Mn2+-cations are monoclinic (space group P21/n). The effect of various structure-forming factors on the M0.5Zr2(PO4)3 compounds with a common structural motif but different symmetries are discussed.

Synthesis, structure, and thermal expansion of sodium zirconium arsenate phosphates

Sodium zirconium arsenate phosphates NaZr2(AsO4)x(PO4)3−x were synthesized by precipitation technique and studied by X-ray diffraction and IR spectroscopy. In the series of NaZr2(AsO4)x(PO4)3−x, continuous substitution solid solutions are formed (0 ≤ x ≤ 3) with the mineral kosnarite structure. The crystal structure of NaZr2(AsO4)1.5(PO4)1.5 was refined by full-profile analysis: space group R

Synthesis and investigation of the new phosphates K2LnZr(PO4)3 (Ln = Ce-Yb, Y) with langbeinite Structure

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Synthesis and properties of LiZr2(AsO4)3 and LiZr2(AsO4) x (PO4)3 − x

c, a = 8.9600(4)Å, c = 22.9770(9) Å, V = 1597.5(1) Å3, Rwp = 4.55. The thermal expansion of the arsenate-phosphate NaZr2(AsO4)1.5(PO4)1.5 and the arsenate NaZr2(AsO4)3 was studied by thermal X-ray diffraction in the temperature range of 20–800°C. The average linear thermal expansion coefficients (αav = 2.45 × 10−6 and 3.91 × 10−6 K−1, respectively) indicate that these salts are medium expansion compounds.

Calcium thorium phosphate (Whitlockite-type mineral). Synthesis and structure refinement

New orthophosphates of potassium, zirconium, and rare earth elements K2LnZr(PO4)3 (Ln = Ce-Yb, Y) that crystallize in a langbeinite structure (cubic system, sp. gr. P213, Z = 4) were prepared and investigated by X-ray diffraction and IR spectroscopy. The structure of the K2PrZr(PO4)3 phosphate was refined by the Rietveld method using neutron powder diffraction data (DN-2 time-of-flight diffractometer, Joint Institute for Nuclear Research, Dubna). This structure is characterized by a mixed framework [PrZr(PO4)3] with large cavities in which potassium cations are located. Pr3+ and Zr4+ cations are distributed in order over two independent crystallographic positions. The limits of the incorporation of lanthanide cations into the anionic framework in phosphates with sodium-zirconium phosphate and langbeinite structures are considered.

Molybdenum Fixation in Crystalline NZP Matrices

The LiZr2(AsO4)3 arsenate and LiZr2(AsO4)x(PO4)3 − x solid solutions have been prepared through precipitation followed by heat treatment, and characterized by X-ray diffraction, X-ray structure analysis, IR spectroscopy, and impedance spectroscopy. We have established conditions for the crystallization of the arsenate and a continuous series of arsenate phosphate solid solutions (0 ≤ x ≤ 3), which have been obtained as two polymorphs: monoclinic and hexagonal. Using the Rietveld method, we have refined the crystal structures of the polymorphs of LiZr2(AsO4)3 (sp. gr. P21/n, a = 9.1064(2), b = 9.1906(2), c = 12.7269(3) Å, β = 90.844(2)°, V =1065.03(5) Å3, Z = 4; sp. gr. R

IR study of the structure of rhombohedral zirconium and alkali metal orthophosphates

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Infrared spectroscopy and the structure of rare-earth chromium borates RCr3(BO3)4 (R = La-Er)

c, a = 9.1600(4), c = 22.9059(13) Å, V = 1664.44(14) Å, Z = 6) and LiZr2(AsO4)1.5(PO4)1.5. Their structural frameworks are built up of AsO4 tetrahedra—or (As,P)O4 tetrahedra occupied by arsenic and phosphorus atoms at random—and ZrO6 octahedra, with the lithium atoms in between. The ionic conductivity of the materials has been measured. The cation conductivity of monoclinic LiZr2(AsO4)x(PO4)3 − x with 0 ≤ x ≤ 1 has been shown to exceed the conductivity of lithium zirconium phosphate.

Synthesis and structural study of Rb2FeZr(PO4)3 phosphate with langbeinite structure

The crystal structure of a new calcium thorium phosphate has been refined by the full-profile Rietveld method using X-ray powder diffraction data. The sample has been synthesized by the sol-gel technique. The phosphate has been identified by X-ray powder diffraction and IR spectroscopy. The refined composition is represented by the formula Ca10.26Th0.12(PO4)7. The CaOn and PO4 polyhedra are distorted compared to the corresponding polyhedra in the basic compound β-Ca3(PO4)2.

Synthesis and Crystal-Chemical Properties of Phosphates BIIRIIIMIV(PO4)3 Containing f, d, and Alkaline-Earth Elements

A possibility of fixation of molybdenum present in spent nuclear fuel in ceramic matrices with the structure of the NaZr2(PO4)3 (NZP) type was studied. The crystallochemical features of molybdenum incorporation into various crystallographic NZP structures depending on the synthesis conditions were considered. New molybdate-phosphates of variable composition Na1-xZrMoxO12 (0 ≤ x ≤ 0.6), crystallizing in the NZP crystal type, were prepared and characterized by X-ray diffraction and IR spectroscopy. The synthesis conditions and the concentration and temperature fields of stability of molybdate-phosphates in the system Na2O-ZrO2-MoO2-P2O5 were studied. The crystallographic parameters of single-phase samples were evaluated. The results obtained suggest that the basic factors of formation of chemically stable single-phase NZP ceramics incorporating MoO42- anions are the composition of wastes and oxidative synthesis conditions.