Crystal structure of β′-Zn2V2O7

The crystal structure of the high-temperature modification of zinc pyrovanadate, namely, β′-Zn₂V₂O₇, is refined by the full-profile Rietveld method (GSAS) using the high-temperature X-ray diffraction data. The crystals are monoclinic (space group C2/m, Z = 2); the unit cell parameters are as follows: a = 6.9324(2) Å, b = 8.4394(2) Å, c = 5.0326(1) Å, and β = 108.272(2)°. Comparative analysis of the crystal structures of β′-Zn₂V₂O₇, β-Mn₂V₂O₇, and Cd₂V₂O₇ is performed.     

Synthesis and electrical properties of new perovskite-like <Emphasis Type="Italic">A</Emphasis>Mn<Subscript>3</Subscript>V<Subscript>4</Subscript>O<Subscript>12</Subscript> (A = Ca,Ce, and Sm) compounds

AMn₃V₄O₁₂ (A = Ca, Ce, and Sm) compounds with a perovskite structure are synthesized at high pressures and temperatures. The crystalline structure of these compounds (space group \(Im\bar 3\)Z = 2) is determined via X-ray analysis. If ions in the A sublattice are changed in the order Ca²⁺–Sm³⁺–Ce³⁺, the valence is redistributed from Ca²⁺Mn₃²⁺V₄⁴⁺O₁₂ to Sm³⁺Mn₃²⁺V₄^3.75+O₁₂, and to Ce³⁺Mn₃²⁺V₄^3.75+O₁₂. The temperature dependences of the electrical resistivity are studied.     

Novel IR Phosphor Based on Sr3La2(Ge3O9)2 : Nd3+,Ho3+ Germanate

Physics of the Solid State - Cyclogermanate Sr3La2(Ge3O9)2, isostructural to silicate Sr3Er2(Si3O9)2, activated by neodymium and holmium is obtained for the first time by the precursor method. Ion...     

Phase transformations of the Re<Subscript>0.3</Subscript>Ir<Subscript>0.7</Subscript> solid solution

Transformations of the nonequilibrium solid solution Re_0.3Ir_0.7 at increased pressure (1–10 GPa) and temperature (2000°C) have been studied. A phase transition from the hexagonal close-packed cell to the face-centered cubic cell without a loss of density and volume per atom has been detected.     

Crystal structure and spectroscopic properties of A[VO2(SO4)(H2O)2] · H2O (A = K, Rb, Tl, NH4) compounds

The crystal structure of dioxovanadium(V) sulfate trihydrates A[VO₂(SO₄)(H₂O)₂] · H₂O, where A is K, Rb, Tl, or NH₄, has been determined based on a combination of neutron and X-ray diffraction data. The compounds are isostructural and have a monoclinic lattice (space group P2₁, Z = 2) with unit cell parameters a = 6.24535(8), 6.26016(7), 6.25817(5), and 6.2500(1) Å; b = 9.8417(1), 9.99736(8), 9.96217(9), and 9.9742(1) Å; c = 6.52113(8), 6.69303(5), 6.70379(6), and 6.70334(9) Å; β = 106.99(1)°, 107.83(1)°, and 107.83(1)°, 107.99(1)°, respectively. The SO₄ tetrahedra and VO₄(H₂O)₂ octahedra share an oxygen vertex to form infinite isolated chains. Atoms A have CN = 10. IR and Raman spectroscopy data are reported.     

Crystal structure and spectroscopic properties of AVO2SO4 (A = K, Rb) compounds

The crystal structure of alkali-metal dioxovanadium(V) sulfates AVO₂SO₄, where A is K or Rb, has been determined based on a combination of neutron and X-ray diffraction data. The compounds are isostructural and have an orthorhombic lattice (space group P2₁2₁2₁, Z = 4) with unit cell parameters a = 11.1004(2) and 10.8193(1) Å; b = 8.2626(2) and 8.9042(1) Å; c = 5.4772(1) and 5.5722(1) Å, respectively. The structures are of the chain type. Zigzag chains are formed by vertex-sharing VO₆ octahedra. Sulfate groups SO₄ link neighboring chains and form a spatial framework with cavities accommodating alkali-metal atoms with CN = 9 (K) and 8 (Rb). IR and Raman spectroscopy data are reported.     

Determination of Osmium Traces in Natural Samples

A method is proposed for the autoclave sample preparation of osmium-containing rocks and ores. The method is compatible with the subsequent diffusion preconcentration of osmium. The best composition of the acid mixture is found for the autoclave decomposition of chromites and other hard-to-decompose materials; the best conditions for the decomposition of rocks are found in order to avoid a loss of osmium at this stage. The detection limits of osmium in chromites are 2.5 ng/g for kinetic determination, 5 ng/g for ICP AES determination, and 0.1 ng/g for ICP MS determination.     

Phosphor for the Near-IR and Short-Wave IR Ranges Based on a Garnet Structured Cubic Modification of Lithium–Lanthanum Niobate

Physics of the Solid State - Cubic garnets activated by neodymium and holmium, Li6CaLa2Nb2O12:Nd3+,Ho3+, were obtained by solid-state method. The main regularities of changes in the luminescence...