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.     

Liquid phosphors POCl3-ZrCl4-235UO 2 2+ -Nd3+

Liquid phosphors POCl₃-ZrCl₄-²³⁵UO ₂ ²⁺ and POCl₃-ZrCl₄-²³⁵UO ₂ ²⁺ -Nd³⁺ with concentrations of Nd³⁺ and UO ₂ ²⁺ of up to 0.75 and 0.12 M were prepared; the lifetime of the Nd³⁺ luminescence was up to 300 μs. The lifetime of the Nd³⁺ luminescence in POCl₃-ZrCl₄-²³⁵UO ₂ ²⁺ -Nd³⁺ solutions decreases with increasing neodymium concentration, and this decrease is more pronounced than that in POCl₃-ZrCl₄-Nd³⁺ solutions. At molar ratio [ZrCl₄]/[Nd³⁺] < 1.5, the luminescence lifetime sharply decreases with decreasing ZrCl₄ concentration. The intensity of the absorption bands of the OH groups observed in the near-IR range of the absorption spectra of POCl₃-ZrCl₄-²³⁵UO ₂ ²⁺ -Nd³⁺ solutions increases with increasing neodymium concentration. Upon storage of POCl₃-ZrCl₄-²³⁵UO ₂ ²⁺ -Nd³⁺ solutions for 2 years without contact with the environment, the intensity of the IR absorption bends of the OH groups gradually increases, whereas the lifetime of the Nd³⁺ luminescence decreases to 60-80 μs.     

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.     

Liquid phosphors POCl3-TiCl4-235UO 2 2+ -Nd3+: 2. Nd3+ luminescence lifetime

Lifetime of the Nd³⁺ luminescence in POCl₃-TiCl₄-²³⁵UO ₂ ²⁺ -Nd³⁺ solutions is almost independent of the concentrations of neodymium and uranyl ions; it attains the maximal value of 220 μs at [TiCl₄] = 0.20?0.35 M and increases with increasing synthesis time, reaching 220 μs at t = 40?60 min. Upon storage, the Nd³⁺ luminescence lifetime decreases by 20–30% in 2 months, and in 2 years it decreases to 60–80 μs in all the samples. Simultaneously with decreasing Nd³⁺ luminescence lifetime, multiple increase in the intensity of the absorption bands of the OH groups is observed in the near-IR range of the absorption spectra of POCl₃-TiCl₄-²³⁵UO ₂ ²⁺ -Nd³⁺ solutions.     

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.     

Liquid luminophores POCl3-SiCl4-235UO 2 2+ -Nd3+

Samples of liquid luminophores POCl₃-SiCl₄-Nd³⁺, POCl₃-SiCl₄-²³⁵UO ₂ ²⁺ , and POCl₃-SiCl₄-²³⁵UO ₂ ²⁺ Nd³⁺ were prepared for the first time. The physicochemical properties and absorption spectra of the samples were compared. The solubility of Nd and U(VI) compounds in the POCl₃ SiCl₄ binary solvent was examined. The Nd³⁺ concentration attains a maximum of 0.3 mM when Nd and U(VI) trifluoroacetates are jointly dissolved at the [POCl₃]/[SiCl₄] molar ratio of 6 8. The shapes of the absorption band of the Nd ions at 860–900 nm, corresponding to the ⁴ I _9/2 → ⁴ F _3/2 electronic transition, differ significantly in POCl₃-SiCl₄-Nd³⁺ and POCl₃-SnCl₄-Nd³⁺ solutions, and in POCl₃-SiCl₄-²³⁵UO ₂ ²⁺ -Nd³⁺ solutions the band shape also depends on the type of the Nd and U(VI) compounds introduced. The near-IR region of the absorption spectra of POCl₃-SiCl₄-²³⁵UO ₂ ²⁺ and POCl₃-SiCl₄-²³⁵UO ₂ ²⁺ -Nd³⁺ solutions contains absorption bands of the OH groups. The band intensity is analyzed in relation to the characteristics of the solutions. The Nd³⁺ luminescence lifetime τ in the luminophores synthesized was estimated at 70–20 μs.     

Reduction of U(VI) in laser liquids POCl3-SnCl4-235UO 2 2+ -Nd3+

U(IV) is irreversibly accumulated during synthesis of laser liquids POCl₃-SnCl₄-²³⁵UO ₂ ²⁺ -Nd³⁺ prepared from various initial Nd(III) and U(VI) compounds, irrespective of the way of their introduction. The rate of U(IV) accumulation in POCl₃-SnCl₄-²³⁵UO ₂ ²⁺ -Nd³⁺ solutions increases with increasing UO ₂ ²⁺ and Nd³⁺ concentrations; for laser liquids with the Nd³⁺ luminescence lifetime τ > 150 μs the observed rate constant of U(IV) accumulation by the second-order reaction k ₂[U⁴⁺] is equal to (3 ± 1) × 10^?5 1 mol^?1 s^?1 at T = 380 K. U(IV) is accumulated during storage of POCl₃-SnCl₄-²³⁵UO ₂ ²⁺ -Nd³⁺ solutions in hermetically sealed glass cells at room temperature and upon irradiation of solutions by xenon lamp light in the spectral region of UO ₂ ²⁺ absorption. The U(VI) reduction proceeds by chemical and photochemical activation of uranyl with formation of stable U⁴⁺ complexes with dichlorophosphate ions and also with Nd³⁺. Deactivation of the uranyl ion excitation with proton-and chlorine-containing impurities prevents U(VI) reduction.     

Synthesis and properties of laser liquids based on POCl3-TlCl3

New laser-active liquids, POCl₃-TlCl₃-Nd³⁺ and POCl₃-TlCl₃-²³⁵UO ₂ ²⁺ -Nd³⁺, were prepared. U(VI) compounds dissolve in POCl₃-TlCl₃ only in the presence of Nd, and in stable solutions [Nd³⁺]/[UO ₂ ²⁺ ] > 4. The experimental data confirm the previously found correlation between the properties of POCl₃-MCl _x -²³⁵UO ₂ ²⁺ -Nd³⁺ solutions and chemical affinity of M ^x+ for oxygen. The radiation-chemical yield of Nd³⁺ in the excited state ⁴ F _3/2 upon homogeneous excitation of POCl₃-TlCl₃-²³⁵UO ₂ ²⁺ -Nd³⁺ solutions with uranium α-radiation increases in proportion with the Nd³⁺ concentration, is independent of the [TlCl₃]/[Nd³⁺] ratio, and is equal to 1 excited ion per 100 eV at [Nd³⁺] = 0.35 M.     

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⁺.     

Synthesis and properties of laser liquids based on POCl3-BCl3

POCl₃-BCl₃ solutions activated with Nd³⁺ and UO ₂ ²⁺ ions were prepared. Significant differences were found in the absorption and luminescence spectra of Nd³⁺ in inorganic laser liquids prepared from different neodymium compounds. In POCl₃-BCl₃-Nd³⁺ solutions prepared from Nd(ClO₄)₃ and Nd(CF₃COO)₃, the half-width of the Nd³⁺ luminescence band corresponding to the main laser transition, ⁴ F _3/2 → ⁴ I _11/2, is 14.0 ± 0.1 and 5.2 ± 0.2 nm, respectively. It is assumed that the Nd³⁺ heterocomplex that is formed in solutions and has uniquely narrow luminescence band incorporates six BCl₃ molecules. The POCl₃-BCl₃-²³⁵UO ₂ ²⁺ -Nd³⁺ solutions have properties typical of POCl₃-MCl _x solutions with halides of metals characterized by high oxygen affinity (M = Zr, Ti, Si, and Al).     

Synthesis and properties of liquid luminophores POCl3-SbCl5-Nd3+ and POCl3-SbCl5-235UO 22+

Luminophores POCl₃-SbCl₅-Nd³⁺ with Nd concentration of up to 0.8 M and Nd³⁺ luminescence lifetime of up to 220 μs and POCl₃-SbCl₅-²³⁵UO ₂ ²⁺ with uranyl concentration of up to 0.16 M were prepared. It was found that stable liquids POCl₃-SbCl₅-Nd³⁺ and POCl₃-SbCl₅-²³⁵UO ₂ ²⁺ can be obtained when salt crystal hydrates are used or water is added to anhydrous Nd and U(VI) compounds. The SbCl₅ content should be 1 ≤ [SbCl₅]/[Nd³⁺] ≤ 2 for the POCl₃-SbCl₅-Nd³⁺ system and [SbCl₅]/[UO ₂ ²⁺ ] > 3 for the POCl₃-SbCl₅-²³⁵UO ₂ ²⁺ system. Based on the solubility of Nd and U(VI) compounds in the POCl₃-SbCl₅ solvent and spectral-luminescence properties of Nd³⁺ and UO ₂ ²⁺ in the luminophores obtained, the following compositions of the complexes formed were suggested: Nd(PO₂Cl₂)_3−y (SbCl_y)_y · xPOCl₃, where y = 1, 2, and 3, and UO₂(PO₂Cl₂)(SbCl₆) · xPOCl₃. Original Russian Text ? G.V. Tikhonov, S.V. Kiselev, 2007, published in Radiokhimiya, 2007, Vol. 49, No. 6, pp. 524–528.     

Thermal reduction of U(VI) in laser liquids based on phosphorus oxychloride

The kinetics of U(VI) reduction in laser liquids POCl₃-SnCl₄-²³⁵UO₂²⁺-Nd³⁺ and POCl₃-SbCl₅-²³⁵UO₂²⁺-Nd³⁺ at 340, 360, and 370 K under the conditions ensuring protection from light was studied. The molar extinction coefficients of U(IV) at λ = 549, 635, 670, and 1148 nm were determined. The rate of U(IV) accumulation increases with temperature and with Nd³⁺ and UO₂²⁺ concentrations. The observed rate constants of U(IV) accumulation in POCl₃-SbCl₅-²³⁵UO₂²⁺-Nd³⁺ are 2–3 times lower than in POCl₃-SnCl₄-²³⁵UO₂²⁺-Nd³⁺. The activation energy of the U(IV) accumulation in the temperature range 340–370 K was 128 and 131 kJ mol⁻¹ for POCl₃-SnCl₄-²³⁵UO₂²⁺-Nd³⁺ and POCl₃-SbCl₅-²³⁵UO₂²⁺-Nd³⁺, respectively. The Stern-Volmer constant of intracomplex nonradiative excitation energy transfer Nd³⁺ → U⁴⁺ amounted to (9.1 ± 1.8) × 10⁵ and (8.4 ± 1.2) × 10⁵ l mol⁻¹ s⁻¹ for POCl₃-SnCl₄-²³⁵UO₂²⁺-Nd³⁺ and POCl₃-SbCl₅-²³⁵UO₂²⁺-Nd³⁺, respectively.     

Reduction of U(VI) in laser liquids based on phosphorus oxychloride in the course of prolonged storage

The kinetic parameters of the reduction U(VI) → U(IV) in laser liquids POCl₃-SnCl₄-²³⁵UO₂²⁺-Nd³⁺ and POCl₃-SbCl₅-²³⁵UO₂²⁺-Nd³⁺ in the course of their prolonged storage at 294 ± 3 K were determined. The rate constant of the U(IV) accumulation depends on particular starting Nd and U(VI) compounds and on the concentration of proton-containing impurities in the liquids. The rate constants of U(IV) accumulation in POCl₃-SnCl₄-²³⁵UO₂²⁺-Nd³⁺ are lower than in POCl₃-SbCl₅-²³⁵UO₂²⁺-Nd³⁺, which correlates with the difference in the oxygen affinities of Sn⁴⁺ and Sb⁵⁺. The activation energy of U(IV) accumulation in POCl₃-SbCl₅-²³⁵UO₂²⁺-Nd³⁺ and POCl₃-SnCl₄-²³⁵UO₂²⁺-Nd³⁺ at 294 ± 3 K was 134 and 175 kJ mol⁻¹, respectively.     

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 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.     

Magnetic properties of LaInO<Subscript>3</Subscript>-based perovskite-structure photoluminescent materials doped with Nd<Superscript>3+</Superscript>, Cr<Superscript>3+</Superscript>, and Mn<Superscript>3+</Superscript> ions

Single-phase ceramic samples of La_1–xNd_xInO₃ (0.007 ≤ x ≤ 0.05), LaIn_0.99M_0.01O₃, and La_0.95Nd_0.05In_0.995M_0.005O₃ (M = Cr³⁺ and Mn³⁺) solid solutions have been prepared by solid-state reactions, and their crystal structure, magnetic field dependences of their specific magnetization at 5 and 300 K, and temperature dependences of their molar magnetic susceptibility have been studied. It has been shown that the 300-K specific magnetization of the La_1–xNd_xInO₃ (x = 0.02, 0.05), La_0.95Nd_0.05In_0.995M_0.005O₃ (M = Cr³⁺ and Mn³⁺), and LaIn_0.99Mn_0.01O₃ solid solutions increases linearly with increasing magnetic field strength up to 14 T and that the magnitude of the 300-K specific magnetization of the La_0.993Nd_0.007InO₃ and LaIn_0.99Cr_0.01O₃ solid solutions increases linearly, but they have diamagnetic magnetization. At a temperature of 5 K, the magnetization of all the indates studied here increases nonlinearly with increasing magnetic field strength, gradually approaching magnetic saturation, without, however, reaching it in a magnetic field of 14 T. In the temperature range where the Curie–Weiss law is obeyed (5–30 K), the effective magnetic moments obtained for the Nd³⁺ ion (\({\mu _{effN{d^{3 + }}}}\)) in the La_1–xNd_xInO₃ solid solutions with x = 0.007, 0.02, and 0.05 are 2.95μ_B, 3.09μ_B, and 2.75μ_B, respectively, which is well below the theoretical value \({\mu _{effN{d^{3 + }}}}\)= 3.62μ_B. The effective magnetic moments of the Cr³⁺ and Mn³⁺ ions in the LaIn_0.99Cr_0.01O₃ and LaIn_0.99Mn_0.01O₃ solid solutions are 3.87μ^B and 5.11μ^B, respectively, and differ only slightly from the theoretical values \({\mu _{effC{r^{3 + }}}}\)= 3.87μ^B and \({\mu _{effM{n^{3 + }}}}\)= 4.9μ^B.     

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.     

Size effect in laser-active solutions based on POCl3-MCl x

The effect of the size of the central atom of a Lewis acid on the spectroscopic and luminescence properties of solutions based on POCl₃-MCl _x (M = B, Al, Si, Ti, Zr, Sn, Sb), activated with Nd³⁺ and ²³⁵UO ₂ ²⁺ , was discovered. With a decrease in the effective ionic radius of M ^x+, the half-width of the Nd³⁺ luminescence band decreases from ～12 nm in POCl₃-ZrCl₄ solutions to 5 nm in POCl₃-BCl₃ solutions.     

Fluid Luminophores POCl3-TiCl4-235UO22+-Nd3+: 1. Synthesis and Absorption Spectra

Samples of fluid luminophores POCl₃-TiCl₄-²³⁵UO₂ ²⁺-Nd³⁺ were prepared for the first time. The absorption spectra of POCl₃-TiCl₄ containing Nd³⁺ and UO₂ ²⁺ ions were studied. The IR spectra exhibited absorption bands that were previously unknown for solutions of phosphorus oxychloride. These bands were identified as overtones 1 and 2 of the stretching vibrations of the OH group. The absorption band grows in intensity with increasing both the synthesis time and the titanium tetrachloride concentration in solution. Changes in the uranyl concentration affect the intensity and position of the Nd3+ absorption band maximum, corresponding to the ⁴ I9/2⁴ F3/2 transition.     

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.