Phase transitions and high-temperature crystal chemistry of polymorphous modifications of Cs<Subscript>2</Subscript>(UO<Subscript>2</Subscript>)<Subscript>2</Subscript>(MoO<Subscript>4</Subscript>)

Phase transitions and thermal deformations of - and -Cs₂(UO₂)₂(MoO₄)₃ were studied by high-temperature X-ray diffraction analysis. In heating of -Cs₂(UO₂)₂(MoO₄)₃ to 625 ± 25°C, the reconstructive phase transition proceeds. -Cs₂(UO₂)₂(MoO₄)₃ is stable up to 700 ±25°C. The thermal expansion of both phases is sharply anisotropic: ₁₁ = 10 × 10^–6, ₂₂ = 33 × 10^–6, ₃₃ = 10 × 10^–6, _V = 53 × 10^–6 deg^–1 for -Cs(UO₂)₂(MoO₄)₃ and ₁₁ = 13 × 10^–6, ₃₃ = 3 × 10^–6, _V = 31 × 10^–6 deg^–1 for -Cs₂ (UO₂)₂ (MoO₄)₃. The anisotropy of thermal expansion is explained by features of the crystal structure of the compounds.Translated from Radiokhimiya, Vol. 46, No. 5, 2004, pp. 405–407.Original Russian Text Copyright © 2004 by Nazarchuk, Krivovichev, Filatov.     

Synthesis and crystal structure of [UO<Subscript>2</Subscript>(OH)(CO(NH<Subscript>2</Subscript>)<Subscript>2</Subscript>)<Subscript>3</Subscript>]<Subscript>2</Subscript>(ClO<Subscript>4</Subscript>)<Subscript>2</Subscript>

The complex [UO₂(OH)(CO(NH₂)₂)₃]₂(ClO₄)₂ (I) was synthesized. A single crystal X-ray diffraction study showed that compound I crystallizes in the triclinic system with the unit cell parameters a = 7.1410(2), b = 10.1097(2), c = 11.0240(4) Å, α = 104.648(1)°, β = 103.088(1)°, γ = 108.549(1)°, space group \(P\bar 1\), Z = 1, R = 0.0193. The uranium-containing structural units of the crystals are binuclear groups [UO₂(OH)· (CO(NH₂)₂)₃] ₂ ²⁺ belonging to crystal-chemical group AM²M ₃ ¹ [A = UO ₂ ²⁺ , M² = OH^?, M¹ = CO(NH₂)₂] of uranyl complexes. The crystal-chemical analysis of nonvalent interactions using the method of molecular Voronoi-Dirichlet polyhedra was performed, and the IR spectra of crystals of I were analyzed.     

Elastic properties of Li<Subscript>2</Subscript>Zn<Subscript>2</Subscript>(MoO<Subscript>4</Subscript>)<Subscript>3</Subscript> single crystals

The complete elastic modulus matrix of Li₂Zn₂(MoO₄)₃ single crystals has been measured for the first time. The sound velocity has been measured in different directions of the crystals by a pulse-phase method. The measurement results have been used to calculate elastic moduli. The sound velocity has been calculated in the three main crystallographic planes of the crystals.     

Na<Subscript>2</Subscript>MoO<Subscript>4</Subscript>-CaMoO<Subscript>4</Subscript>-Ce<Subscript>2/3</Subscript>MoO<Subscript>4</Subscript> scheelite-like solid solutions

We have studied tetragonal scheelite-like solid solutions in the ternary system Na₂MoO₄-CaMoO₄-Ce_2/3MoO₄: Na _0.7Ca_y Ce_{1.1 ? 2y/3} (MoO₄)₂ (0 ≤ y ≤ 0.6) and Na_0.3 Ca_zCe_{1.23? 2z/3} (MoO₄)₂ (0 ≤ z ≤ 1.4). The solid solutions melt congruently at temperatures from 1100 to 1200°C. Their lattice parameters have been determined. Using reflection spectra, we evaluated the color parameters of all the samples studied.     

Specific absorption coefficient of chromium in (TeO<Subscript>2</Subscript>)<Subscript>0.80</Subscript>(MoO<Subscript>3</Subscript>)<Subscript>0.20</Subscript> glass

We have prepared (TeO₂)_0.80(MoO₃)_0.20 glass samples containing 0.01 to 0.11 wt % chromium and determined their optical transmission in the range from 450 to 2800 nm. The glasses have been shown to have a strong absorption band centered at 660 nm. From the attenuation coefficient as a function of Cr³⁺ concentration in the glasses, we have evaluated their specific absorption coefficient, which has been shown to be 190 ± 2 cm^–1/wt % at the maximum of the absorption band.     

Crystal structure of KNa<Subscript>3</Subscript>[(UO<Subscript>2</Subscript>)<Subscript>5</Subscript>O<Subscript>6</Subscript>(SO<Subscript>4</Subscript>)]

The crystal structure of a previously unknown compound KNa₃[(UO₂)₅O₆(SO₄)] [space group Pbca, a = 13.2855(15), b = 13.7258(18), c = 19.712(2) Å, V = 3594.6(7) ų] was solved by direct methods and refined to R ₁ = 0.055 for 3022 reflections with |F _hkl | ≥ 4σ |F _hkl |. In the structure there are five sym-metrically nonequivalent uranyl cations. They are linked by cationcation (CC) interactions to form a pentamer whose central cation is U(2)O ₂ ²⁺ forming two three-centered CC bonds. All the uranyl ions are coordinated in the equatorial plane by five O atoms, which leads to the formation of pentagonal bipyramids sharing common edges to form layers parallel to the (100) plane. The sulfate tetrahedron links the uranyl layers into a 3D framework. The K⁺ and Na⁺ cations are arranged in framework voids. A brief review of CC interactions in U(VI) compounds is presented.     

Synthesis and study of uranyl phosphates (UO<Subscript>2</Subscript>)<Subscript>3</Subscript>(PO<Subscript>4</Subscript>)<Subscript>2</Subscript>·<Emphasis Type="Italic">n</Emphasis>H<Subscript>2</Subscript>O

Uranyl phosphate (UO₂)₃(PO₄)₂·8H₂O was synthezied. Its dehydration was studied by X-ray diffraction, IR spectroscopy, and thermal and chemical analysis. The dehydration products were isolated and characterized by X-ray diffraction and IR spectroscopy. Their structural features were determined.     

Microstructure of (Na<Subscript>0.5</Subscript>La<Subscript>0.5</Subscript>)MoO<Subscript>4</Subscript> crystals coactivated with cerium and erbium ions

Crystals with the scheelite structure have been grown by the Czochralski technique from a melt of composition (Na_0.5La_0.345Ce_0.15Er_0.005)MoO₄ (NLM:Ce,Er) and have been characterized by scanning and transmission electron microscopy and x-ray microanalysis. The crystals are shown to contain carbon inclusions and CeO₂ precipitates, the latter oriented relative to the host matrix: [100]{0\(\bar 1\)2} NLM:Ce,Er ‖ [100]{0\(\bar 1\)1} CeO₂. High-temperature annealing leads to recrystallization and growth of the CeO₂ particles, which seems to be responsible for the adverse effect of annealing on the optical quality of the crystals.     

Synthesis and crystal structure CoNi<Subscript>2</Subscript>(BO<Subscript>3</Subscript>)<Subscript>2</Subscript>

A new metal orthoborate compound, cobalt dinickel orthoborate, CoNi₂(BO₃)₂ has been successfully synthesized for the first time. The title compound was synthesized by thermally-induced solid-state chemical reaction at 900°C between the initial reagents of Co(NO₃)₂ · 6H₂O, Ni(NO₃)₂ · 6H₂O and H₃BO₃ which were mixed with the mol ratio of 1: 2: 2 respectively. The obtained product was structurally characterized by X-ray powder diffraction technique. It has been found that the CoNi₂(BO₃)₂ crystallizes in the kotoite type and isostructural with the compounds having the chemical formula M₃(BO₃)₂ where M—Mg, Co and Ni. The synthesized compound belongs to the orthorhombic crystal system with the refined unit cell parameters of a = 5.419(9) Å, b = 8.352(0) Å, c = 4.478(8) Å and Z = 2. The space group was determined as Pnmn. Further characterizations by FTIR, elemental analysis and thermal analysis were also performed.     

Synthesis,crystal structure,and absorption spectra of a complex neptunium(v) chromate,Na<Subscript>3</Subscript>[NpO<Subscript>2</Subscript>(CrO<Subscript>4</Subscript>)<Subscript>2</Subscript>](H<Subscript>2</Subscript>O)<Subscript>5</Subscript>

A new Np(V) chromate complex with outer-sphere sodium cations, Na₃[NpO₂(CrO₄)₂](H₂O)₅ (I), was synthesized from aqueous solution. Its composition and structure were determined by single crystal X-ray diffraction. The structure of I is based on anionic chains of the composition [NpO₂(CrO4)2] _n ³ⁿ⁻, running along [010] and forming layers parallel to the (101) plane. The Na⁺ ions and water molecules of crystallization are arranged between the layers. The coordination polyhedra of the Np atoms (pentagonal bipyramids) are combined pairwise by sharing common equatorial edges formed by two bridging oxygen atoms of bidentate chelate-bridging CrO₄ groups. The absorption spectra of I in the IR and visible ranges are presented.     

Graphene oxide-decorated Fe<Subscript>2</Subscript>(MoO<Subscript>4</Subscript>)<Subscript>3</Subscript> microflowers as a promising anode for lithium and sodium storage

Mixed transition metal oxides (MTMOs) have received intensive attention as promising anode materials for lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs). In this work, we demonstrate a facile one-step water-bath method for the preparation of graphene oxide (GO) decorated Fe₂(MoO₄)₃ (FMO) microflower composite (FMO/GO), in which the FMO is constructed by numerous nanosheets. The resulting FMO/GO exhibits excellent electrochemical performances in both LIBs and SIBs. As the anode material for LIBs, the FMO/GO delivers a high capacity of 1,220 mAh·g^–1 at 200 mA·g^–1 after 50 cycles and a capacity of 685 mAh·g^–1 at a high current density of 10 A·g^–1. As the anode material for SIBs, the FMO/GO shows an initial discharge capacity of 571 mAh·g^–1 at 100 mA·g^–1, maintaining a discharge capacity of 307 mAh·g^–1 after 100 cycles. The promising performance is attributed to the good electrical transport from the intimate contact between FMO and graphene oxide. This work indicates that the FMO/GO composite is a promising anode for high-performance lithium and sodium storage.

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Synthesis and structure of (NH<Subscript>4</Subscript>)<Subscript>3</Subscript>[UO<Subscript>2</Subscript>(CH<Subscript>3</Subscript>COO)<Subscript>3</Subscript>]<Subscript>2</Subscript>(NCS)

The compound (NH₄)₃[UO₂(CH₃COO)₃]₂(NCS) (I) was synthesized and examined by single crystal X-ray diffraction analysis. The compound crystallizes in the rhombic system with the unit cell parameters a = 11.5546(4), b = 18.5548(7), c = 6.7222(3) Å, V = 1441.19(10) ų, space group P2₁2₁2, Z = 2, R = 0.0345. The uranium-containing structural units of crystals of I are isolated mononuclear groups [UO₂(CH₃COO)₃]^? belonging to crystal-chemical group AB ₃ ⁰¹ (A = UO ₂ ²⁺ , B⁰¹ = CH₃COO^?) of uranyl complexes. The specific features of packing of the uranium-containing complexes in the crystal structure are considered.     

Ce and Eu activated Na<Subscript>2</Subscript>Zn<Subscript>5</Subscript>(PO<Subscript>4</Subscript>)<Subscript>4</Subscript>, a new promising novel phosphor

A new efficient phosphor, Eu²⁺/Eu³⁺ and Ce³⁺ activated Na₂Zn₅(PO₄)₄ has been synthesized by solid-state reaction technique at high temperature. X-ray powder diffraction analysis confirmed the formation of Na₂Zn₅(PO₄)₄ host lattice. Scanning electron microscopy indicated that the microstructure of the phosphor consisted of irregular fine grains with a size of about 0·5–2 μm. Photoluminescence excitation spectrum measurements of Ce³⁺ activated Na₂Zn₅(PO₄)₄ show that the phosphor can be efficiently excited by UV-Vis light from 280 to 310 nm to realize emission in the visible (blue) range due to the 5d-4f transition of Ce³⁺ ions which is applicable for scintillation purpose, whereas Eu²⁺/Eu³⁺ activated Na₂Zn₅(PO₄)₄ phosphor emits blue, green and red emission spectrum shows at 487 nm, 546 nm with a dominant peak at 611 nm respectively, due to Eu²⁺/Eu³⁺ ions which is promising candidate for solid state lighting. Therefore, newly synthesised, by low cost and easy technique prepared, novel phosphors may be useful as RGB phosphor for solid state lighting application.     

Electrical Conductivity and Electrochemical Characteristics of Na<Subscript>3</Subscript>V<Subscript>2</Subscript>(PO<Subscript>4</Subscript>)<Subscript>3</Subscript>-Based NASICON-Type Materials

NASICON-type materials with the compositions Na₃V_2–xAl_x(PO₄)₃, Na₃V_{2 - x}Fe_x(PO₄)₃, Na_{3 + x}V_2–xNi_x(PO₄)₃, and Na₃V_{2 - x}Cr_x(PO₄)₃ (x = 0, 0.03, 0.05, and 0.1) have been prepared and characterized by X-ray diffraction analysis, electron microscopy, and impedance spectroscopy. The results demonstrate that the highest electrical conductivity among the samples studied is offered by the material doped with 5% Fe: Na₃V_1.9Fe_0.1(PO₄)₃. The activation energy for low-temperature conduction in the doped materials decreases from 84 ± 2 to 54 ± 1 kJ/mol and that for high-temperature conduction is ~33 kJ/mol. The discharge capacity of Na₃V_1.9Fe_0.1(PO₄)₃/C under typical working conditions of cathodes of sodium ion batteries has been shown to exceed that of Na₃V₂(PO₄)₃/C. The capacity of the more porous material prepared by the Pechini process (Na₃V_1.9Fe_0.1(PO₄)₃/C-{II}) approaches the theoretical one at a low charge–discharge rate and retains its high level as the charge rate is raised (its discharge capacity was 117.6, 108.8, and 82.6 mAh/g at a discharge rate of 0.1C, 2C, and 8C, respectively).     

Liquid-phase epitaxy of NdAl<Subscript>3</Subscript>(BO<Subscript>3</Subscript>)<Subscript>4</Subscript> and Yb-doped YAl<Subscript>3</Subscript>(BO<Subscript>3</Subscript>)<Subscript>4</Subscript>

Epitaxial layers of NaAl₃(BO₃)₄ (NAB) and YAl₃(BO₃)₄〈Yb〉 (YAB〈Yb〉) containing up to 10 at % Yb have been grown by liquid-phase epitaxy on YAB substrates. Their growth kinetics have been studied at relative supersaturations of the high-temperature solution from 2 × 10^?2 to 16 × 10^?2. The ytterbium concentration in YAB〈Yb〉 has been shown to vary little during the epitaxial process. Near the edges of the substrate, the surface morphology of the layers is complicated by vicinals, which have a spiral form in the case of YAB〈Yb〉. On \(\{ 10\overline 1 1\} \) YAB substrates, homogeneous single-crystal NAB films have been grown.     

Synthesis and crystal structure of Cu<Subscript>2</Subscript>{(UO<Subscript>2</Subscript>)<Subscript>3</Subscript>[(S,Cr)O<Subscript>4</Subscript>]<Subscript>5</Subscript>}(H<Subscript>2</Subscript>O)<Subscript>17</Subscript>

Cu₂{(UO₂)₃[(S,Cr)O₄]₅}(H₂O)₁₇ crystals were prepared by evaporation of aqueous solutions. The crystal structure was solved by the direct method and refined to R ₁ = 0.064 (wR ₂ = 0.177) for 8120 reflections with ¦F _hkl¦ 4 ¦F _hkl¦. Rhombic system, space group Pbca, a = 18.0586(8), b = 19.9898(9), c = 20.5553(8) Å, V = 7420.2(6) ų. The structure is based on {(UO₂)₃[(S,Cr)O₄]₅}^4– anionic layers, formed by combination of UO₇ pentagonal bipyramids and TO₄ tetrahedra through common vertices. The { (UO₂)₃ [(S,Cr)O₄]₅}^4– layers are parallel to the (010) plane. The Cu²⁺ (H₂O)₆ octahedra and additional water molecules are located in the interplanar space and provide binding of the layers in the structure by hydrogen bonds. Based on the occupancy of tetrahedral positions, more accurate chemical formula of the compound should be written as Cu₂{(UO₂)₃[(S_0.804 Cr_0.196)O₄]₅} (H₂O)₁₇.Translated from Radiokhimiya, Vol. 46, No. 5, 2004, pp. 408–411.Original Russian Text Copyright © 2004 by Krivovichev, Burns.     

Crystal structure of a complex of Pu(VI) nitrate with triphenylphosphine oxide, [PuO<Subscript>2</Subscript>(NO<Subscript>3</Subscript>)<Subscript>2</Subscript>(OP(C<Subscript>6</Subscript>H<Subscript>5</Subscript>)<Subscript>3</Subscript>)<Subscript>2</Subscript>]

Single crystals of [PuO₂(NO₃)₂(TPPO)₂] (TPPO = OPPh₃) isostructural to the related compounds of uranyl and neptunyl were isolated, and the structure of this complex was determined. Contrary to the complexes [AnO₂(TPPO)₄](ClO₄)₂ studied previously, the interatomic distances and volumes of coordination polyhedra of An in these compounds somewhat decrease in the series U-Np-Pu. This difference was attributed to a change in the number of TPPO ligands in the compounds and weakening of their interaction with oxygen atoms of the AnO ₂ ²⁺ groups in passing from [AnO₂(TPPO)₂](ClO₄)₂ to [AnO₂(No₃)₂(TPPO)₂].     

Beta-LaSc<Subscript>3</Subscript>(BO<Subscript>3</Subscript>)<Subscript>4</Subscript>: correction of the crystal structure

The published structure data of trigonal beta-LaSc₃(BO₃)₄ are incorrect because they are not compatible with the formula of the compound. After correcting the positional atom co-ordinates of one O atom the structure is found to be isotypic with CeSc₃(BO₃)₄ which crystallizes with the huntite CaMg₃(CO₃)₄ structure type.Response to paper, titled "Structure of medium temperature phase -LaSc₃(BO₃)₄ crystal," by He MY et al., published in MRI, vol. 2, issue 6, pp. 345–348, DOI     

Acousto-optic properties of LiBi(MoO<Subscript>4</Subscript>)<Subscript>2</Subscript> single crystals grown at low temperature gradients

This paper reports the starting charge composition and process parameters for low thermal gradient (<1°C/cm) Czochralski growth of uniform bulk LiBi(MoO₄)₂ crystals. The acousto-optic figure of merit (M ₂) of a LiBi(MoO₄)₂ crystal has been measured in different directions.     

Thermodynamic properties of NaZr<Subscript>2</Subscript>(AsO<Subscript>4</Subscript>)<Subscript>3</Subscript>

The heat capacity C _p ⁰ of crystalline NaZr₂(AsO₄)₃ has been measured in the range 7–650 K using precision adiabatic calorimetry and differential scanning calorimetry. The experimental data have been used to calculate the standard thermodynamic functions of the arsenate: C _p ⁰, enthalpy H ⁰(T) − H ⁰(0), entropy S ⁰(T), and Gibbs function G ⁰(T) − H ⁰(0) from T → 0 to 650 K. The standard entropy of its formation from elements is Δ_f S ⁰(NaZr₂(AsO₄)₃, cr, 298.15 K) = −1087 ± 1 J/(mol K).