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.     

Synthesis and properties of laser-active liquids POCl<Subscript>3</Subscript>-SbCl<Subscript>5</Subscript>-<Superscript>235</Superscript>UO<Stack><Subscript>2</Subscript><Superscript>2+</Superscript></Stack>-Nd<Superscript>3+</Superscript>

The effect of the synthesis conditions on the properties of inorganic laser-active liquids POCl₃-SbCl₅-²³⁵UO ₂ ²⁺ -Nd³⁺ is considered. The kinetic dependences of the U(IV) content and decay time of the Nd³⁺ luminescence in POCl₃-SbCl₅-²³⁵UO ₂ ²⁺ -Nd³⁺ solutions for various synthesis procedures at 380 K have been obtained. In POCl₃-SbCl₅-²³⁵UO ₂ ²⁺ -Nd³⁺ solutions, nonradiative energy transfer Nd³⁺ → U⁴⁺ is observed, and quenching of the Nd³⁺ luminescence is described by the Stern-Volmer law: k _q = (6.4 ± 0.6) × 10⁵ l mol^?1 s^?1. Laser liquids POCl₃-SbCl₅-²³⁵UO ₂ ²⁺ -Nd³⁺ with neodymium concentration of up to 0.7 M, uranyl concentration of up to 0.1 M, and decay time of the Nd³⁺ luminescence of up to 220 μs have been prepared for the first time.     

Interaction of aqueous UO<Stack><Subscript>2</Subscript><Superscript>2+</Superscript></Stack> solutions with sorbents based on modified silica gel containing Cu,Ni, and Zn

Interaction of aqueous UO ₂ ²⁺ solutions with modified sorbents based on coarsely porous silica gel MSKG, containing Cu, Ni, and Zn ions, was studied. Uranyl ions are sorbed on all the sorbents. The decontamination factors of 10^?2 M aqueous UO ₂ ²⁺ solutions on straight MSKG and on MSKG modified with Cu, Ni, and Zn are of the same order of magnitude and do not exceed 100. In the case of 1.1 × 10^?1 M UO ₂ ²⁺ solutions, the decontamination factors on straight MSKG and on MSKG modified with Cu, Ni, and Zn are also of the same order of magnitude but do not exceed 10. Interaction of the modified Ni-containing sorbent with a UO ₂ ²⁺ solution results in formation of a swamp-green precipitate of the composition NiU(OH)₆·4N₂H₅OH, i.e., UO ₂ ²⁺ is reduced to U⁴⁺.     

Luminescence properties of uranyl in POCl<Subscript>3</Subscript>-SnCl<Subscript>4</Subscript> solvent

The spectral-luminescence properties of uranyl in aprotic binary solvent POCl₃-SnCl₄ were studied. The uranyl luminescence lifetime τ in the POCl₃-SnCl₄-²³⁵UO ₂ ²⁺ system does not exceed 20 μs. There is no concentration quenching of uranyl up to [UO ₂ ²⁺ ] = 0.14 M. When anhydrous UO₃ is dissolved, τ increases with increasing water content of the initial solvent,. In the solutions containing uranyl perchlorate, τ decreases with increasing uranyl and SnCl₄ concentrations. This effect is caused by products of ClO ₄ ^? decomposition scavenged by SnCl₄.     

Synthesis and properties of liquid luminophores based on the POCl<Subscript>3</Subscript>-BiCl<Subscript>3</Subscript>-MCl<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> system

Stable BiCl₃-containing solutions of phosphorus oxychloride, activated with UO ₂ ²⁺ and Nd³⁺ ions, can be prepared only in the presence of another Lewis acid MCl _x . The electronic absorption spectra of the liquids prepared and the decay times of the Nd³⁺ luminescence are characteristic of individual solutions based on POCl₃-MCl _x . The radiation-chemical yield of Nd³⁺ in the excited state ⁴ F _3/2 in POCl₃-BiCl₃-MCl _x -²³⁵UO ₂ ²⁺ -Nd³⁺ solutions upon homogeneous excitation with uranium α-particles is lower than in POCl₃-MCl _x -²³⁵UO ₂ ²⁺ -Nd³⁺ solutions at comparable component concentrations. Apparently, Bi³⁺ in solutions based on the POCl₃-BiCl₃-MCl _x system is not incorporated in neodymium- and/or uranyl-containing complexes and remains in the matrix.     

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.     

Tailoring magnetic and dielectric properties of Co<Subscript>0.9</Subscript>Cu<Subscript>0.1</Subscript>Fe<Subscript>2</Subscript>O<Subscript>4</Subscript> with substitution of small fractions of Gd<Superscript>3+</Superscript> ions

This paper describes the structural, magnetic, and dielectric properties of Gd³⁺ substituted cobalt–copper ferrite. The influence of Gd³⁺ substitution on the structural, magnetic and electrical properties of cobalt–copper ferrite was investigated through various characterization techniques. Thermal analysis was carried out on the prepared gel to know the combustion and calcination temperature. The detailed structural analysis suggests that the substitution of a Fe³⁺ ion with a Gd³⁺ ion at B site results in lattice distortion, modification in crystallite size and grain size of the material. X-ray photoelectron spectroscopy confirmed the oxidation states of the elements present. Magnetic measurement performed at 300 and 50 K depicts the decrease in saturation magnetization (Ms) and increase in coercivity (Hc) with Gd³⁺ substitution in the cobalt–copper spinel ferrite. The dielectric measurements acquired over a wide range of frequencies and temperature showed an increase in dielectric constant with increasing Gd³⁺ concentration.     

The calorimetry and thermodynamic functions of Nd Mg<Stack><Subscript>3</Subscript><Superscript>I</Superscript></Stack>Mn<Subscript>4</Subscript>O<Subscript>12</Subscript> (Me<Superscript>I</Superscript>-Li,Na, K) manganites in the range from 298.15 to 673 K

The ceramic technology is employed for synthesizing manganites of composition Nd Mg ₃ ^I Mg₃Mn₄O₁₂(Me^I-Li, Na, K). The X-ray technique is used to find that the compounds crystallize in tetragonal syngony. The parameters of their crystal lattices are determined. Their heat capacities are experimentally determined in the range from 298.15 to 673 K, which enables one to reveal second-order phase transitions. In view of these transitions, equations describing the C _p ^° ～ f(T) dependence are derived, and the thermodynamic functions C _p ^° (T), H°(T)-H°(298.15), S°(T), and Φ ^xx (T) are calculated.     

Oxidation of Np(V) with Xenon Trioxide in an HClO<Subscript>4</Subscript> Solution

Oxidation of Np(V) to Np(VI) with xenon trioxide in a 0.5–1.4 M HClO₄ solution was studied by spectrophotometry. The reaction rate is described by the equation–d[Np(V)]/dt = k[Np(V)][XeO₃], where k = 4.6 × 10^–3 L mol^–1 s^–1 in 1 M HClO₄ at 92°С. The activation energy is close to 92 kJ mol^–1. The activated complex is formed in contact of NpO ₂ ⁺ and ХеО₃ without participation of Н⁺ ions. The activated complex transforms into NpO ₂ ²⁺ and the products: ОН, Хе, and О₂. The ОН radical oxidizes Np(V). Admixtures of Со²⁺ and especially Fe³⁺ accelerate the Np(V) oxidation.     

Reduction of U(VI) in POCl<Subscript>3</Subscript>-lewis acid solutions

Features of the behavior of uranyl ions in POC1₃-MCl _x -²³⁵UO ₂₊ ² solutions (M = Ti, Si, Zr, Sn, Sb) were considered. Irreversible accumulation of U(IV) in the course of synthesis of POCl₃-SnCl₄-²³⁵UO ₂₊ ² solutions prepared from water-containing U(VI) compounds, excluding UO₂(ClO₄)₂ · 5H₂O, was found. The reaction rate increases with increasing uranyl concentration, k _l[U(IV)] ～ (1.6±0.2) × 10^?6 s^?1 (T = 380 K). The U(IV) accumulation was also observed on heating (T = 360–380 K) POCl₃-SnCl₄-²³⁵UO ₂₊ ² and POCl₃-SbCl₅-²³⁵UO ₂₊ ² solutions hermetically sealed in glass cells and on irradiating them by the light of a xenon lamp. In POCl₃-SbCl₅-²³⁵UO ₂₊ ² solutions prepared from UO₂(C1O₄)₂ · 5H₂O, U(IV) disappears within several days after stopping the irradiation. The reduction of U(VI) is caused by formation of uranyl dichlorophosphate complexes and by deactivation of uranyl excitation with chlorine-containing agents.     

Compounds WAl<Subscript>4</Subscript>, WAl<Subscript>3</Subscript>, W<Subscript>3</Subscript>Al<Subscript>7</Subscript>, and WAl<Subscript>2</Subscript> and Al-W-N combustion products

X-ray diffraction data are presented for combustion products in the Al-W-N system. New, nonequilibrium intermetallic compounds have been identified, their diffraction patterns have been indexed, and their unit-cell parameters have been determined. The phases α-and β-WAl₄ are shown to exist in three isomorphous forms, differing in unit-cell centering. The phases α′-, α″-, and α?-WAl₄ are monoclinic, with a ₀ = 5.272 Å, b ₀ = 17.770 Å, c ₀ = 5.218 Å, β = 100.10°; point groups C12/c1, A12/n1, I12/a1, respectively. The phases β′-, β″-, and β?-WAl₄ are monoclinic, with a ₀ = 5.465 Å, b ₀ = 12.814 Å, c ₀ = 5.428 Å, β = 105.92°; point groups A112/m, B112/m, I112/m, respectively. The compounds WAl₂ and W₃Al₇, identified each in two isomorphous forms, differ in cell metrics (doubling) but possess the same point group: P222. WAl ₂ ^′ : orthorhombic, a ₀ = 5.793 Å, b ₀ = 3.740 Å, c ₀ = 6.852 Å. WAl ₂ ^″ : orthorhombic, a ₀ = 11.586 Å, b ₀ = 3.740 Å, c ₀ = 6.852 Å. W₃Al ₇ ^′ : orthorhombic, Pmm2, a ₀ = 6.225 Å, b ₀ = 4.806 Å, c ₀ = 4.437 Å. W₃Al ₇ ^″ : orthorhombic, Pmm2, a ₀ = 12.500 Å, b ₀ = 4.806 Å, c ₀ = 8.874 Å. The new phase WAl₃: triclinic, P1, a ₀ = 8.642 Å, b ₀ = 10.872 Å, c ₀ = 5.478 Å, α = 104.02°, β = 64.90°, γ = 107.15°.     

Enhanced magnetoelectric coupling in La-modified Bi<Subscript>5</Subscript>Co<Subscript>0.5</Subscript>Fe<Subscript>0.5</Subscript>Ti<Subscript>3</Subscript>O<Subscript>15</Subscript> multiferroic ceramics

Multiferroic properties of La-modified four-layered perovskite Bi_5?x La _x Fe_0.5Co_0.5Ti₃O₁₅ (0 ≤ x ≤ 1) ceramics were investigated, by analyzing the magnetodielectric effect, magneto-polarization response and magnetoelectric conversion. X-ray diffraction indicated the formation of pure Aurivillius ceramics, and Raman spectroscopy revealed the Bi ions displacement and the crystal structure variation. The enhancement of ferromagnetic and ferroelectric properties was observed in Bi_5?x La _x Fe_0.5Co_0.5Ti₃O₁₅ after La modification. The evidence for enhanced ME coupling was determined by magnetic field-induced marked variations in the dielectric constant and polarization. A maximum ME coefficient of 1.15 mV/cm·Oe was achieved in Bi_4.25La_0.75Fe_0.5Co_0.5Ti₃O₁₅ ceramic, which provides the possible promise for novel magnetoelectric device application.     

Scaling behavior of dynamic hysteresis in Bi<Subscript>3.15</Subscript>Nd<Subscript>0.85</Subscript>Ti<Subscript>3</Subscript>O<Subscript>12</Subscript> ceramics

The scaling behavior of dynamic hysteresis was investigated in Bi_3.15Nd_0.85Ti₃O₁₂ bulk ceramics at a frequency of 1–1000 Hz and an external electric field amplitude of 79–221 kV/cm. The scaling behavior at low amplitude (E ₀ ≤ 114 kV/cm) takes the form of \(\langle A \rangle \propto f^{ - 0.013} E_{0}^{0.7}\) for low frequency (f ≤ 200 Hz) and \(\langle A \rangle \propto f^{ - 0.013} E_{0}^{0.22}\) for high frequency (f > 200 Hz), where \(\langle A \rangle\) is the area of hysteresis loop and f and E ₀ are frequency and amplitude of external electric field, respectively. At high amplitude (E ₀ > 114 kV/cm), we obtain \(\langle A \rangle \propto f^{0.011} E_{0}^{1.163}\) at low frequency and \(\langle A \rangle \propto f^{ - 0.015} E_{0}^{0.7}\) at high frequency. At low E ₀, the contribution to the scaling relation mainly results from reversible domain switching, while at high E ₀ reversible and irreversible domain switching concurrently contribute to the scaling relation.     

Influence of isovalent and heterovalent substitution for Bi<Superscript>3+</Superscript> and Fe<Superscript>3+</Superscript> on the properties of Bi<Subscript>2</Subscript>Fe<Subscript>4</Subscript>O<Subscript>9</Subscript>-based solid solutions

Bi_2–хLa_хFe₄O₉ and Bi₂Fe_4–2xTi_xCo_xO₉ ferrites have been prepared by solid-state reactions at a temperature of 1073 K. X-ray diffraction data indicate that, in the Bi_2–хLa_хFe₄O₉ system, the limiting degree of La³⁺ substitution for Bi³⁺ ions in Bi₂Fe₄O₉ does not exceed 0.05 and that the limiting degree of substitution in the Bi₂Fe_4–2xTi_xCo_xO₉ system lies in the range 0.05 < x < 0.1. The specific magnetization and specific magnetic susceptibility of the samples have been measured at temperatures from 5 to 300 K in a magnetic field of 0.86 T. The field dependences of magnetization obtained for the Bi_2–хLa_хFe₄O₉ and Bi₂Fe_4–2xTi_xCo_xO₉ ferrites at temperatures of 300 and 5 K demonstrate that partial isovalent substitution of La³⁺ for Bi³⁺ ions in Bi₂Fe₄O₉ and heterovalent substitution of Ti⁴⁺ and Co²⁺ ions for two Fe³⁺ ions leads to partial breakdown of the antiferromagnetic state and nucleation of a ferromagnetic state.     

Effect of NaOH Concentration and Adding Sequences on Structural and Magnetic Properties of Ni<Subscript>0.4</Subscript>Co<Subscript>0.6</Subscript>Fe<Subscript>2</Subscript>O<Subscript>4</Subscript> Nanopowders Prepared Via Co-precipitation Route

Ni_0.4Co_0.6Fe₂O₄ nanopowders were prepared via the co-precipitation route followed by annealing treatment. The structural and magnetic properties of the as-synthesized samples were determined by XRD, FT-IR, TG-DSC, and PPMS measurements, respectively. The XRD patterns indicated a single-phase cubic spinel structure for all the Ni-Co ferrite samples, regardless of adding sequences of the reactants or NaOH concentration. The analysis of the XRD patterns revealed that the enhancement in lattice constant with increasing NaOH concentration is related to the prevention of oxidization of Co²⁺ ions in the Ni-Co ferrite lattice. The FT-IR spectra indicated that samples prepared in the B process have fewer impurities than those prepared in the A process. The enhancement in saturation magnetization with the increase in sodium hydroxide concentration could be attributed to the strengthening of super-exchange interaction between A and B sublattices, due to replacements of Co³⁺ ions (magnetic moment of 0 μ _B) by Co²⁺ ions (magnetic moment of 3 μ _B) at B sublattices. The obvious increase in the coercivity field with the increase in concentration of NaOH solutions can be interpreted in terms of enhancement of magneto-crystalline anisotropy that originated from gradual substitutions of Co³⁺ ions with Co²⁺ ions at the octahedral sites.     

The magnetic properties of BiY<Subscript>2</Subscript>Fe<Subscript>5</Subscript>O<Subscript>12</Subscript> nanoparticles doped with Cr ions

BiY₂Cr _x Fe_5?x O₁₂ (x = 0, 0.05, 0.1, 0.2, 0.3) nanocrystals were synthesized by using a sol-gel method. Samples were characterized by the powder X-ray diffraction (XRD), the thermal gravity analysis (TGA) and the differential thermal analysis (DTA), the vibrating sample magnetometer(VSM) and Mössbauer spectrums. The average sizes of the particles were determined by the Scherrer’s formula. The special Ms and Mössbauer spectra of BiY₂Cr _x Fe_5?x O₁₂ nanocrystals are researched at room temperature. It is seen that the special Mss of samples are initially increased with increasing Cr³⁺ content (x < 0.1), and decreased with increasing content of Cr³⁺ ions (x > 0.1).     

Effect of Ti-ion non-stoichiometry on microstructure and microwave dielectric characteristic of Li<Subscript>2</Subscript>ZnTi<Subscript>3</Subscript>O<Subscript>8</Subscript> ceramics

This paper studies the microwave dielectric properties, microstructure, vibration and densification of Li₂ZnTi_3+xO_8+2x (\(- 0.04 \le {\text{x}} \le +0.06\)) ceramics, manufactured via a conventional mixed oxide route. The X-ray diffraction and Raman spectroscopy revealed the unit cell parameter and cation ordering in LZT non-stoichiometry in their vibrational modes. The densification and phase composition were characterized by the EDX and SEM methods. It was found that a slight Ti vacancy can improve the relative density to the maximum value (96.2%). The XRD results showed that the second phase of TiO₂ in the Li₂ZnTi_3.06O_8.12 composition is formed. The sintered samples were detected in the microwave frequency range by using the resonance technique. The \({\text{~}}{\tau _f}\) values of the ceramics within Ti excess adjusted to near zero. The Li₂ZnTi_2.96O_7.92 ceramic showed the best relative density, single phase and best microwave dielectric \({\varepsilon _r}~={\text{ }}25.98\), Q?×?f?=?61,000 GHz, \({\tau _f}={\text{ }} - 17.4{\text{ ppm/}}^\circ {\text{C}}\) sintered at 1100 °C for 4 h.     

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.     

Kinetics of Technetium Reactions: XV. Tc(IV) Oxidation with Persulfate Ions in HClO<Subscript>4</Subscript> Solution

Tc(IV) is oxidized with persulfate ions in HClO₄ solution by reactions with both S₂O ₈ ²⁻ ion and product of its thermal decomposition, Caro acid, H₂SO⁵. The reaction rate at 35°C and solution ionic strength μ = 1 is described by the equation d[Tc(IV)]/dt = k ₁[Tc(IV)][S₂O ₈ ²⁻ ] + k ₃[Tc(IV)][HSO ₅ ⁻ ]/[H⁺], where k ₁ = 0.88±0.04 l mol⁻¹ min⁻¹ and k ₃ = 110±5 min⁻¹. With increasing ionic strength to μ = 2, both rate constants decrease (k ₁ = 0.58±0.08 l mol⁻¹ min⁻¹ and k ₃ = 52±2 min⁻¹ at 35°C). The activation energy of the overall reaction is 77.7±8.1 kJ mol⁻¹. The mechanisms of both reactions are discussed. __________ Translated from Radiokhimiya, Vol. 47, No. 2, 2005, pp. 145–149. Original Russian Text Copyright ? 2005 by V. Koltunov, Gomonova, G. Koltunov.     

Synthesis and characterization of magnetic and microwave absorbing properties in polycrystalline cobalt zinc ferrite (Co<Subscript>0.5</Subscript>Zn<Subscript>0.5</Subscript>Fe<Subscript>2</Subscript>O<Subscript>4</Subscript>) composite

In this research work, magnetic and microwave absorption loss and other response characteristics in cobalt zinc ferrite composite has been studied. Cobalt zinc ferrite with the composition of Co_0.5Zn_0.5Fe₂O₄ was prepared via high energy ball milling followed by sintering. Phase characteristics of the as-prepared sample by using XRD analysis shows evidently that a high crystalline ferrite has been formed with the assists of thermal energy by sintering at 1250 °C which subsequently changes the magnetic properties of the ferrite. A high magnetic permeability and losses was obtained from ferrite with zinc content. Zn substitution into cobalt ferrite has altered the cation distribution between A and B sites in spinel ferrite which contributed to higher magnetic properties. Specifically, Co_0.5Zn_0.5Fe₂O₄ provides electromagnetic wave absorption characteristics. It was found that cobalt zinc ferrite sample is highly potential for microwave absorber which showed the highest reflection loss (RL) value of ??24.5 dB at 8.6 GHz. This material can potentially minimize EMI interferences in the measured frequency range, and was therefore used as fillers in the prepared composite that is applied for microwave absorbing material.