- Study of the system Pr2O3-SeO2-H2O at 100°C and the properties of the compounds obtained
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The solubility of the system Pr2O3-SeO2-H2O at 100°C was studied. The fields of crystallization of Pr2(SeO3)3·H2O, PrH(SeO3)2, Pr(HSeO3/sub
- Gospodinov,Stancheva
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- Kinetics of isothermal decomposition of ZnSeO3 and CdSeO 3
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The kinetics of decomposition of ZnSeO3 and CdSeO3 was studied under isothermal heating on a derivatograph. The values of activation energy, pre-exponential factor in Arrhenius equation and change of entropy were calculated for the formation of the activated complex by the reagent. The dependencies observed are interpreted according to the generalized perturbation theory of chemical reactivity.
- Vlaev,Georgieva,Gospodinov
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- The synthesis and crystal structures of the first rare-earth alkaline-earth selenite chlorides MNd10(SeO3)12Cl8 (M=Ca and Sr)
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Two new alkaline-earth Nd selenite chlorides MNd10(SeO3)12Cl8 (M=Ca, Sr) were obtained using crystal growth from alkaline-earth chloride melts in quartz tubes. These new compounds crystallize in the orthorhombic system in space group C cca (#68). The compounds were studied by energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction. It was shown that both compounds adopt the same structure type, constructed by complex [M11(SeO3)12]8+ slabs separated by chloride anion layers perpendicular to the longest cell parameter. The SeO3 groups show a pyramidal shape and may be described as SeO3E tetrahedra. Such SeO3 groups decorate the Nd-O skeletons forming the [M11(SeO3)12]8+ slabs.
- Berdonosov,Olenev,Dolgikh,Lightfoot
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- A study of the selenites of cerium phase states in aqueous medium and thermal properties
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The solubilities of the systems CeO2-SeO2-H 2O and Ce2O3-SeO2-H2O were studied at 100°C. The field of crystallization of Ce(SeO 3)2 was established in the system CeO2-SeO 2-H2O, and fields of crystallization of Ce 2(SeO3)3 and Ce2(SeO 3)3 H2SeO3 were established in the system Ce2O3-SeO2-H2O. The compound obtained were identified by means of chemical, X-ray and derivatograph analysis. The mechanism of thermal dissociation of Ce(SeO3)2, Ce2(SeO3)3 and Ce2(SeO 3)3H2SeO3 was studied.
- Gospodinov,Stancheva
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- Structural and thermal studies on the solid products in the system MnSeO3-SeO2-H2O
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The solubility of MnSeO3-SeO2-H2O system was studied in the temperature region 25-300°C. The compounds of the three-component system were identified by the Schreinemaker's method. The phase diagram of manganese(II) selenit
- Vlaev,Tavlieva, Mariana P.
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- Mild Hydrothermal Synthesis of Cu(SeO3).2H2O: Structural Characterization, Thermal, Spectroscopic and Magnetic Studies
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Cu(SeO3).2H2O has been synthesized by hydrothermal technique under autogeneous pressure. The compound crystallizes in the P212121 orthorhombic space group. The unit cell parameters are a = 6.672(1), b
- Larranaga, Aitor,Mesa, Jose L.,Lezama, Luis,Arriortua, Maria I.,Rojo, Teofilo
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- Cadmium copper selenite chloride, CdCu2(SeO3)2Cl2, an insulating spin gap system
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Novel copper cadmium selenite chloride has been synthesized via vapor transport reaction as well as by solid state process. CdCu2(SeO3)2Cl2 crystallizes in a monoclinic space group I2/a with cell constants a ?= ?7.8057(3) ?, b ?= ?9.6036(4) ?, c ?= ?10.7817(5) ? and β ?= ?102.362(4)°, Z ?= ?4. Its crystal structure can be described as an open channel three-dimensional framework, formed by [CdO2Cl4] and [CuO4Cl2] polyhedra interconnected by pyramidal SeO3 groups. The copper polyhedra form magnetically isolated dimers with a spin gap Δ ?= ?38.7 ?± ?0.8 ?meV, as defined from magnetic susceptibility measurements. The electron band gap estimated by diffuse reflectance method Eg ?= ?2.82 ?± ?0.02 ?eV is in agreement with the yellow-green color of the substance. Density functional theory provides the values of electron (2.4 ?eV) and spin (36.6 ?meV) gaps consistent with experimental observations.
- Berdonosov, Peter S.,Danilovich, Igor L.,Dolgikh, Valery A.,Murtazoev, Alisher F.,Pchelkina, Zlata V.,Tafeenko, Victor A.,Vasiliev, Alexander N.
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- Syntheses, structures, and properties of Ag4(Mo2O5)(SeO4)2(SeO3) and Ag2(MoO3)3SeO3
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Ag4(Mo2O5)(SeO4)2(SeO3) has been synthesized by reacting AgNO3, MoO3, and selenic acid under mild hydrothermal conditions. The structure of this compound consists of cis-MoO22+ molybdenyl units that are bridged to neighboring molybdenyl moieties by selenate anions and by a bridging oxo anion. These dimeric units are joined by selenite anions to yield zigzag one-dimensional chains that extended down the c-axis. Individual chains are polar with the C2 distortion of the Mo(VI) octahedra aligning on one side of each chain. However, the overall structure is centrosymmetric because neighboring chains have opposite alignment of the C2 distortion. Upon heating Ag4(Mo2O5)(SeO4)2(SeO3) looses SeO2 in two distinct steps to yield Ag2MoO4. Crystallographic data: (193 K; MoKα, λ=0.71073 A): orthorhombic, space group Pbcm, a=5.6557(3), b=15.8904(7), c=15.7938(7) A, V=1419.41(12), Z=4, R(F)=2.72% for 121 parameters with 1829 reflections with I>2σ(I). Ag2(MoO3)3SeO3 was synthesized by reacting AgNO3 with MoO3, SeO2, and HF under hydrothermal conditions. The structure of Ag2(MoO3)3SeO3 consists of three crystallographically unique Mo(VI) centers that are in 2+2+2 coordination environments with two long, two intermediate, and two short bonds. These MoO6 units are connected to form a molybdenyl ribbon that extends along the c-axis. These ribbons are further connected together through tridentate selenite anions to form two-dimensional layers in the [bc] plane. Crystallographic data: (193 K; MoKα, λ=0.71073 A): monoclinic, space group P21/n, a=7.7034(5), b=11.1485(8), c=12.7500(9) A, β=105.018(1) V=1002.7(2), Z=4, R(F)=3.45% for 164 parameters with 2454 reflections with I>2σ(I). Ag2(MoO3)3SeO3 decomposes to Ag2Mo3O10 on heating above 550 °C.
- Ling, Jie,Albrecht-Schmitt, Thomas E.
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- Synthesis and structural, spectroscopic and magnetic studies of two new polymorphs of Mn(SeO3)·H2O
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Two new manganese(II) selenite polymorphs with formula Mn(SeO 3)·H2O have been synthesized by slow evaporation from an aqueous solution. The crystal structure of both compounds (1) and (2) have been solved from X-ray diffraction data. The structure of (1) was determined from single-crystal X-ray diffraction techniques. The compound crystallizes in the Ama2 space group, with a=5.817(1), b=13.449(3), c=4.8765(9)A and Z=4. The structure of (2) has been solved from X-ray powder diffraction data. This phase crystallizes in the P21/n space group with unit-cell parameters of a=4.921(3), b=13.121(7), c=5.816(1)A, β=90.03(2)° and Z=4. Both polymorphs exhibit a layered structure formed by isolated sheets of MnO6 octahedra and (SeO3) 2- trigonal pyramids in the (010) plane. These layers, which contain one manganese and selenium atom crystallographically independent, are formed by octahedra linked between them through the selenite oxoanions. The difference of both compounds consists in the stacking of the layers along the b-axis. The IR spectra show the characteristic bands of the selenite anion. Studies of luminescence performed at 6 K and diffuse reflectance spectroscopy have been carried out for both phases. The Dq and Racah (B and C) parameters, from luminescence and diffuse reflectance spectroscopy, are Dq=705, B=750, C=3325cm-1 for (1) and Dq=720, B=745, C=3350cm-1 for (2). The ESR spectra of both compounds are isotropic with g-values of 1.99(1). Magnetic measurements indicate the presence of antiferromagnetic couplings in both phases. The J-exchange parameters have been estimated by fitting the experimental magnetic data to a model for square-planar lattice. The values obtained are J/k=-0.83, -0.91 K and J′/k=-0.97, -1.20 K, for polymorphs (1) and (2), respectively.
- Larranaga, Aitor,Mesa, Jose L.,Pizarro, Jose L.,Pena,Olazcuaga, Roger,Arriortua, Maria I.,Rojo, Teofilo
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- Pressure-induced structural deformations in SeO2
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The high-pressure behavior of low-dimensional selenium dioxide SeO2 (P42/mbc, Z = 8) is studied with Raman scattering and synchrotron angle-dispersive X-ray powder diffraction in a diamond anvil cell up to 23 GPa at room temperature. Pressure-induced transformations in this material involve a sequence of structural distortions of the chain structure. The transformation occuring above 7.0 GPa is due to symmetry lowering to space group Pbam (Z = 8) without major changes of the crystal lattice dimensions and coordination around the Se atoms. Like in the ambient pressure polymorph, the structural unit is a SeO3E polyhedron, where E is a Se non-bonded electron lone pair, or an irregular tetrahedron with the O atoms and Se lone pair at the vertices. Further structural transitions above 17 GPa are likely to be the result of additional distortions leading to monoclinic symmetry of the crystal structure. All transformations are reversible with little hysteresis.
- Grzechnik, Andrzej,Farina,Lauck,Syassen,Loa,Bouvier
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- Age-induced phase transitions on mechanically alloyed amorphous GaSe
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After aging it for four years at room temperature, a mechanically alloyed amorphous GaSe powder was transformed to a multi-phase crystalline alloy, where major phase is the trigonal Se one. The structural, thermal and optical properties of this aged amorphous GaSe were investigated through systematic X-ray diffraction, differential scanning calorimetry and Raman scattering measurements. The X-ray diffraction results on the aged GaSe powder suggest the presence of oxides, and X-ray absorption spectroscopy was employed to further investigate it.
- Campos,de Lima,Grandi,Souza,Pizani
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- Oxidation of polycrystalline zinc selenide with atmospheric oxygen
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Oxidation of granulated polycrystalline zinc selenide (grain size 0.2-6.5 mm) with atmospheric oxygen at 430-700°C was studied. The optimal conditions for the oxidation were found. An installation for the oxidation of kilogram amounts of zinc selenide was
- Khlopochkina,Gaivoronskii,Gavrishchuk,Elliev,Yashina
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- Thermal and other studies on bivalent metal selenites
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BaSeO3·2.5H2O(I), PbSeO3·2H2O(II) and CdSeO3·3.5H2O(III) were prepared and analysed. Their hygroscopicity and solubility were investigated. These compounds have high thermal stability, as s
- Verma,Khushu
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- Polymorphism in mercury(I) selenite(IV): Preparation, crystal structures of α-, β-and γ-Hg2SeO3, and thermal behavior of the α- and β-modification
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Mercury(I) selenite(IV) is polymorphic and crystallizes at least in three modifications, named α-, β-and γ-Hg2SeO3. Polycrystalline β-Hg2SeO3 was prepared by precipitation of a concentrated mercurous nitrate solution with selenous acid. Hydrothermal treatment of the colorless β-Hg2SeO3 powder in demineralized water at 250°C (10days) yields light-yellow single crystals of α-Hg2SeO3 which show the highest density of the three modifications. Colorless needle-shaped single crystals of β-Hg2SeO3 and very few single crystals of γ-Hg2SeO3 co-crystallize from strongly diluted Hg2(NO3)2 and H2SeO3 solutions and were grown by a diffusion technique. All crystal structures were solved and refined from single crystal diffractometer data sets and are based on Hg22+ dumbbells and trigonal pyramidal SeO32- anions as the main building units. A common structural feature of all modifications is the formation of open channels extending parallel to the shortest crystallographic axis. The non-bonding orbitals of the SeIV atoms are stereochemically active and protrude into the channels. Upon heating in an open system under N2 atmosphere, both α- and β-Hg2SeO3 decompose in a well-separated three-step mechanism. The first step (T > 250°C) involves disproportionation into elementary mercury and α-HgSeO3 which at ca. 400°C subsequently transforms into β-HgSeO3. The second step between T = 400 and 500°C is accompanied by a loss of Hg and SeO2 and the formation of the basic salt Hg3SeO6. In the third step, at temperatures between T = 500° and 600°C, this material decomposes completely. Upon heating in a closed system (sealed silica capillaries), β-Hg2SeO3 transforms between 320-340°C into the more dense α-Hg2SeO3 which on further heating likewise converts into elementary mercury and β-HgSeO3.
- Weil, Matthias
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- Quartz-crystal microbalance study of the growth of Zn(Se,O) thin-films in a chemical bath. A sequential electroless-chemical process
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The chemical bath deposition of Zn(Se,O) thin films is studied with a quartz crystal microbalance (QCM). The deposition velocity is measured with QCM under different experimental conditions, including substrate properties, bath temperature and bath composition. The plots of the growth velocity vs. time reflect the sequence of processes for the deposition of the film. At the beginning, an induction period takes place, which ends up with the formation of first ZnSe particles. These particles activate an electroless reaction induced by a reducer, hydrazine or hydroxide, which gives rise to deposition of a film with ZnO and ZnSe composition. This step is necessary to attain compact and thicker films with appropriate conditions for solar cell application. The electroless mechanism is decelerated after deposition of some nanometers of film, hence, a second growth mechanism starts to predominate consisting in the chemical reaction of soluble selenide with hydroxide and Zn2+ cations on the substrate surface. The layers resulting from this second mechanism have higher proportion of ZnSe than the previously electroless generated layers. At longer times, the predominant growth mechanism is the deposition of ZnSe clusters formed in the solution, which produces less compact and poorly adherent top layers. This sequence of mechanisms gives rise to films with heterogeneous morphology and composition in depth.
- Chaparro,Gutiérrez,Herrero
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- Synthesis, thermal, spectroscopic and magnetic studies of the Mn(SeO3)·2H2O and Fe2(SeO3)3·3H2O selenites
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Mn(SeO3)·2H2O (1) and Fe2(SeO3)3·3H2O (2) have been synthesized by slow evaporation from an aqueous solution in the case of (1) and using mild hydrothermal conditions for (2). The crystal structures of both phases have been refined by the Rietveld method. The compounds crystallize in different spatial groups, the P21/n monoclinic one with parameters a = 6.649(1) A, b = 6.542(1) A, c = 10.890(1) A and β = 103.85(1)° being Z = 4 for (1) and the R3c trigonal space group with parameters a = 9.361(1) A, c = 20.276(1) A and Z = 6 for (2). The crystal structure of compound (1) consists of a three-dimensional framework formed by MnO6 octahedra and (SeO3)2- oxoanions with trigonal pyramidal geometry, which gives rise to Mn2O10 dimers of edge-sharing octahedra. The crystal structure of phase (2) can be described as a three-dimensional framework formed by MnO6 octahedra and (SeO3)2- oxoanions with trigonal pyramidal geometry. In this phase the octahedral entities are linked along the three crystallographic axes through the selenite anions. Diffuse reflectance spectrum and luminescent measurements for (1) indicate the existence of Mn2+ cations in a slightly distorted octahedral environment. Diffuse reflectance spectrum and Moessbauer spectroscopy, in the paramagnetic region, for (2) show the existence of Fe3+ cations in slightly distorted octahedral symmetry. ESR spectra of both compounds are isotropic with a g-value of 1.99(1) and 2.00(1), respectively. Magnetic measurements of both phases indicate an antiferromagnetic behavior. For phase (2), both, the ESR and magnetic measurements suggest a spin change from Fe3+ (S = 5/2) to Fe2+ (S = 2) at low temperatures.
- Larranaga, Aitor,Mesa, Jose L.,Pizarro, Jose L.,Lezama, Luis,Arriortua, Maria I.,Rojo, Teofilo
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- Thermodynamic properties and rare-earth spectroscopy of Cu3Nd(SeO3)2O2X (X = Cl, Br)
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The kagome lattice of copper ions in francisite-type compounds is quite sensitive to external stimuli, being easily affected by temperature and magnetic field. The rare-earth ions inserted between buckled layers of transition metal add new dimension to ma
- Markina, Maria M.,Zakharov, Konstantin V.,Berdonosov, Peter S.,Dolgikh, Valery A.,Kuznetsova, Elena S.,Klimin, Sergei A.,Yumashev, Oleg B.,Vasiliev, Alexander N.
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- Supercritical hydrothermal synthesis of Cu2O(SeO3): Structural characterization, thermal, spectroscopic and magnetic studies
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Cu2O(SeO3) has been synthesized in supercritical hydrothermal conditions, using an externally heated steel reactor with coupled hydraulic pump for the application of high pressure. The compound crystallizes in the P213 cub
- Larra?aga, Aitor,Mesa, José L.,Lezama, Luis,Pizarro, José L.,Arriortua, María I.,Rojo, Teófilo
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- Synthesis and powder X-ray diffraction analysis of new mixed rare-earth and selenium oxychlorides with composition LnSeO3Cl
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A series of new mixed rare-earth and selenium oxychlorides with composition LnSeO3Cl (Ln = La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb, or Y) were prepared by annealing together LnOCl and SeO2 in sealed silica tubes. The resulting compounds were characterized by powder X-ray diffraction. The unit cell parameters of the phases were determined. Lanthanum - europium oxychlorides crystallized in the tetragonal system to give the Sillen phases analogously to tellurium compounds with the similar formula, whereas Tb-Yb and Y oxychlorides crystallized in the orthorhombic system. It is likely that the latter oxychlorides are not layered compounds.
- Shabalin,Berdonosov,Dolgikh,Oppermann,Schmidt,Popovkin
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- Evaluation of titanium dioxide and cerium oxide as anodes for the electrooxidation of toluene: A theoretical approach of the electrode process
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Cerium oxide and titanium dioxide were prepared by thermal decomposition of the precursor salts and thermal treatment of titanium plates. In aqueous medium, the metal oxides show a well-defined electrochemical reaction; a solid state redox process takes place in the cathodic range of potentials and only water discharge reaction occurs in the anodic region. At the experimental conditions, the prepared materials were not totally active for the electrooxidation of toluene. The theoretical modeling suggests that the lack of activity is due to the weak interaction between toluene and the metal oxide surface.
- D'Elia, Luis F.,Rincón,Ortíz
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- Synthesis and structure of cyclic selenium oxide SeVISe2IVO7
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Nitromethane is the only presently known organic solvent for highly reactive selenium trioxide (SeO3)4. The stability of the solutions is limited and the beginning of the reaction between both components depends significantly on conc
- Touzin,Kilian,Zak
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- Physicochemical study of the compounds in the three-component system Sc2O3-SeO2-H2O AT 100°C
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The selenites of scandium are used as new materials in producing instrument and semi-conductor engineering. Like tellurites, they can also be applied as materials for making lasers. The process of producing scandium selenides by the reduction of the corresponding selenites has the advantage of taking place at relatively low temperatures and high rate. In this respect, it is necessary to command methods of obtaining high-purity selenites and to obtain data concerning their thermal stability. A physicochemical study of the system Sc2O3-SeO2-H2O was carried out at 100°C in order to find solutions to these problems. The possible compounds in the system at a given temperature were obtained. The compounds were identified by the Schreinemakers' method and also by chemical and X-ray phase analyses. The mechanism of thermal decomposition was determined by means of a derivatograph.
- Gospodinov,Stancheva
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- Strontium nickel and barium nickel selenites: Synthesis and X-ray diffraction parameters
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A new strontium nickel selenite, Sr2Ni(SeO3) 3, was prepared and structurally characterized. The compound crystallizes in triclinic system (space group P1?, a = 7.2860(10) ?, b = 7.581(2) ?, c = 8.722(2) ?, α = 103.02(2)°, β = 105.580(10)°, γ = 95.260(10)°, Z = 2) and is isostructural to cobalt and copper analogues. The structure of Sr2Ni(SeO 3)3 is a three-dimensional framework built of eight-vertex polyhedra [SrO8] and distorted octahedra [NiO6] sharing edges and vertices. The framework channels accommodate selenium atoms bonded to the framework oxygen atoms. The selenite groups SeO3 are pyramidal, which is indicative of high stereochemical activity of the Se(IV) lone pair. The possibility of replacement of some Ni atoms by Cu in Sr2Ni(SeO 3)3 was studied. The search for analogous barium phases did not reveal such compounds, but BaM(SeO3)2 phases were found, where M = Co, Ni, or Cu. The unit cell parameters of the new selenite BaM(SeO3)2 were determined: space group Pnma, a = 14.989(5) ?, b = 5.439(2) ?, c = 7.161(3) ?, Z = 4.
- Berdonosov,Batunin,Olenev,Dolgikh
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- Thermochemical investigation of RE2O3-SeO2 systems. III. Yttrium selenium oxides in the pseudo-binary system
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Ternary pure phases in the thermodynamical equilibrium Y2SexO3+2x in the pseudo-binary Y2O3-SeO2 system have been synthesized by solid state reactions and characterized by X-ray powder diffraction, IR spectroscopy and DSC measurements. A new phase Y2Se3.5O10 was found besides the known phases Y2Se4O11, Y2Se3O9 and Y2SeO5. The thermal decomposition properties of the compounds have been determined by total pressure measurements and their thermodynamics data have been derived from their decomposition functions and Cp values. The phase diagram and the phase barogram have been established.
- Zhang-Presse,Oppermann
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- Study on the kinetics of isothermal decomposition of selenites from IVB group of the periodic system
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The thermal stability and kinetics of isothermal decomposition of the selenites of germanium, tin and lead was studied. A dependence between the process activation energy and the radius and electron polarizability of the cations was observed. It was explained with the different degree of the effect of counterpolarization of the selenite anion. The negative value of the change of entropy of activation showed that the active complex is more complicated formation than the reagent. The higher absolute value of the change of entropy measured for the formation of the active complex Ge(SeO3)2 compared to that for Sn(SeO3)2 shows that the degree of rearrangement (necessary changes) of the initial crystalline structure increases with the decrease of cation radius. The isothermal decomposition of the selenites from IVB group of the periodic system was considered to be 'slow' reaction due to the significantly lower than unity values of the steric factor.
- Vlaev,Gospodinov,Genieva
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- Two new octahedral/pyramidal frameworks containing both cation channels and lone-pair channels: Syntheses and structures of Ba2Mn IIMn2III(SeO3)6 and PbFe2(SeO3)4
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The hydrothermal syntheses, single crystal structures, and some properties of Ba2MnIIMn2III(SeO 3)6 and PbFe2(SeO3)4 are reported. These related phases contain three-dimensional frameworks of vertex (FeO6) and vertex/edge linked (MnO6) octahedra and SeO3 pyramids. In each case, the MO6/SeO3 framework encloses two types of 8 ring channels, one of which encapsulates the extra-framework cations and one of which provides space for the SeIV lone pairs. Crystal data: Ba2Mn3(SeO3) 6, Mr=1201.22, monoclinic, P21/c (No. 14), a=5.4717 (3) A, b=9.0636 (4) A, c=17.6586 (9) A, β=94.519 (1)°, V=873.03 (8) A3, Z=2, R(F)=0.031, wR(F 2)=0.070; PbFe2(SeO3)4, M r=826.73, triclinic, P1- (No. 2), a=5.2318 (5) A, b=6.7925 (6) A, c=7.6445 (7) A, α=94.300 (2)°, β=90.613 (2)°, γ=95.224 (2)°, V=269.73 (4) A3, Z=1, R(F)=0.051, wR(F2)=0.131. Polyhedral view of the structure of the mixed valence barium manganese selenite Ba 2Mn3(SeO3)6 projected onto (100).
- Johnston, Magnus G.,Harrison, William T.A.
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- Study of the compounds present in the three-component system Dy2O3-SeO2-H2O at 100 °C
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The solubility isotherm of the system Dy2O3-SeO2-H2O at 100 °C was studied and drawn. The selenites present in the system were identified and isolated. A thorough TG, DTG and DTA analysis was made. By modelling the conditions of TG, DTG and DTA analysis, the phases of the thermal decomposition were isolated and identified. The chemistry of the reaction was described.
- Gospodinov,Stancheva
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- Thermal analysis of the selenites of the ternary system Nd 2O3-SeO2-H2O at 100°C
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The solubility isotherm of the system Nd2O3-SeO 2-H2O at 100°C was studied and drawn. All possible selenites of neodymium were obtained and characterized. Thermal decomposition of all phases in the system was st
- Gospodinov,Stancheva
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- Synthesis, structure, and properties of V2O3(XO 4)2 (X = S, Se)
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Compounds described as V2O3(XO4) 2, where X = S or Se, were prepared from vanadium(V) oxide mixtures with concentrated sulfuric and selenic acids. The physicochemical properties of the products were studied; for V2O3(SeO4) 2, the crystal structure was determined by powder X-ray diffraction and neutron diffraction, and its key differences from the structure of V 2O3(SO4)2 were identified. V 2O3(SeO4)2 crystallizes in the monoclinic system with the unit cell parameters a = 15.3831(2)?, b = 5.54096(5)?, c = 9.71644(7)?, β = 111.886(1)°, V = 768.51?3, space group C2/c (no. 15).
- Tyutyunnik,Krasil'Nikov,Zubkov,Perelyaeva,Baklanova
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- New quaternary tellurite and selenite: Synthesis, structure, and characterization of centrosymmetric InVTe2O8 and noncentrosymmetric InVSe2O8
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Two new quaternary mixed metal oxide materials-InVTe2O 8 and InVSe2O8-have been synthesized, as crystals and pure bulk powders by standard solid-state reactions using In 2O3, V2O5, and TeO2 (or SeO2) as reagents. The crystal structures of the reported materials were determined using single-crystal X-ray diffraction. InVTe2O 8 crystallizes in the monoclinic centrosymmetric space group P2 1/n (No. 14), with unit-cell parameters of a = 7.8967(16) A, b = 5.1388(10) A, c = 16.711(3) A, β = 94.22(3)°, and Z = 4, and InVSe2O8 crystallizes in the noncentrosymmetric space group Pm (No. 6) with unit-cell parameters of a = 4.6348(9) A, b = 6.9111(14) A, c = 10.507(2) A, β = 97.77(3)°, and Z = 2. While the centrosymmetric InVTe2O8 shows a two-dimensional (2D) layered structure composed of InO6 octahedra, VO4 tetrahedra, and TeO4 polyhedra, the noncentrosymmetric InVSe 2O8 exhibits a three-dimensional (3D) framework structure with distorted InO6 octahedra, VO5 square pyramids, and SeO3 polyhedra. Powder second-harmonic generation (SHG) measurements on InVSe2O8, using 1064-nm radiation, indicate that the material has a SHG efficiency ~30 times that of α-SiO2. Additional SHG measurements reveal that the material is not phase-matchable (Type 1). Infrared, ultraviolet-visible light (UV-vis) diffuse reflectance, and thermogravimetric analyses for the two compounds are also presented, as are dipole moment calculations.
- Lee, Dong Woo,Oh, Seung-Jin,Halasyamani, P. Shiv,Ok, Kang Min
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- Bi6(SeO3)3O5Br2: A new bismuth oxo-selenite bromide
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A new bismuth oxo-selenite bromide Bi6(SeO3) 3O5Br2 was synthesized and structurally characterized. The crystal structure belongs to the triclinic system (space group P1, Z=2, a=7.1253(7) A, b=10.972(1) A, c=12.117(1) A, α=67.765(7)°, β=82.188(8)°, γ=78.445(7)°) and is unrelated to those of other known oxo-selenite halides. It can be considered as an open framework composed of BiOx or BiOyBrz polyhedrons forming channels running along [1 0 0] direction which contain the selenium atoms in pyramidal shape oxygen coordination (SeO3E). The spectroscopic properties and thermal stability were studied. The new compound is stable up to 400 °C.
- Berdonosov, Peter S.,Kirsanova, Maria A.,Dolgikh, Valery A.,Olenev, Andrei V.,Lebed, Julia B.
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- Thermochemical investigations on the pseudobinary system YbOCl/SeO 2
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On the pseudobinary section YbOCl/SeO2 four thermodynamically stable compounds exist in accordance with the thermal decomposition and the phase analysis of defined powder mixtures: YbOCl·3 SeO2 = YbSe3O7Cl, YbOC
- Schmidt,Quoc, H. Dao,Oppermann,Ruck,Berdonosov,Dolgikh,Popovkin
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- Formation and thermal stability of selenites and hydrogen selenites of samarium
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The solubility isotherm of the Sm2O3-SeO 2-H2O system was studied at 100°C. The two compounds obtained in the three-component system were identified by the Schreinemakers' method as well as by chemical, thermoan
- Gospodinov,Stancheva
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- Copper lanthanide selenite oxohalides with francisite structure: Synthesis and structural characteristics
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The reaction of lanthanide oxohalides with CuO and SeO2 gave the products Cu3Ln(SeO3)2O2X (Ln = lanthanide, X = Cl, Br). The oxochlorides are formed with all lanthanides, while oxobromides are formed
- Berdonosov,Dolgikh
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p. 1353 - 1358
(2009/05/06)
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- Kinetic parameters of decomposition of some selenites: Generalized perturbation theory of chemical reactivity
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Studying the kinetics of isothermal decomposition of thirteen selenites at isothermal heating, the values of activation energy E of the process, pre-exponential factor A in Arrhenius equation and changes of entropy Δ S≠ for the formation of the activated complex of the reagent were calculated. Direct dependence between the thermal stability of the selenites and their cation radii on their 'hardness' or 'softness' was found. The dependence was interpreted in the terms of the generalized perturbation theory of chemical reactivity. Kinetic compensation effect was observed only for the selenites, which thermally decompose by the same mechanism.
- Vlaev,Georgieva,Genieva
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p. 421 - 427
(2008/10/09)
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- Study of the crystallization fields of nickel(II) selenites in the system NiSeO3-SeO2-H2O
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The solubility of NiSeO3-SeO2-H2O system in the temperature region 298-573 K was studied. The compounds of the three-component system were identified by the Schreinemakers' method. The phase diagram of nickel(II) selenites
- Vlaev,Genieva, Svetlana D.,Georgieva, Velyana G.
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p. 449 - 456
(2008/10/09)
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- In situ X-ray photoelectron spectroscopy study of the oxidation of CuGaSe2
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The thermal and native oxidation of CuGaSe2 thin films was studied by in situ X-ray photoelectron spectroscopy (XPS). The special design of the XPS chamber allowed to measure XP-spectra under oxidizing gas atmospheres at pressures of up to 5 mb
- Würz,Rusu,Schedel-Niedrig,Lux-Steiner,Bluhm,H?vecker,Kleimenov,Knop-Gericke,Schl?gl
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- Native oxidation of CuGaSe2 crystals and thin films studied by electron paramagnetic resonance and photoelectron spectroscopy
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The oxidation of CuGaSe2 crystals and polycrystalline thin films was investigated with electron paramagnetic resonance (EPR) and photoelectron spectroscopy (PES). An EPR signal assigned to Cu2+ evolves when the samples were stored under ambient conditions for a few months, independent of the morphology of the specimens. The formation of a native oxide layer consisting of Ga2O3 and SeO2 was observed in PES during the initial stage of oxidation. Only after long term oxidation for several months an additional copper hydroxide phase, Cu(OH)2, was detected. When the Cu(OH)2 phase was reduced by annealing in vacuum at 200 °C or removed by etching in KCN also the Cu2+ EPR signal disappeared. It is shown that the Cu2+ EPR signal originates from the Cu(OH)2 phase and the activation energy for the thermal reduction of Cu2+ to nonparamagnetic Cu+ is Ea=0.29 eV. A model for the native oxidation of CuGaSe2 will be presented and implications for solar cell device performance discussed.
- Wuerz, R.,Meeder, A.,Fuertes Marron, D.,Schedel-Niedrig, Th.,Knop-Gericke, A.,Lips, K.
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- The kinetics of dehydration of some selenites under nonisothermal conditions
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The kinetics of dehydration of H2SeO3, Na 2SeO3·5H2O·CoSeO 3·2H2O, and NiSeO3·2H 2O under nonisothermal conditions was studied on a derivatograph. A mathematical procedure implementing the Horowitz-Metzger and Coats-Redfern methods was used. The activation energies, frequency factors, entropies, enthalpies, and Gibbs energies of formation of activated complexes from the reagents were compared.
- Vlaev,Genieva,Gospodinov
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p. 1410 - 1415
(2007/10/03)
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- Thermochemical investigations on systems M2O3/SeO2 - Determination of specific heat capacities
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The experimental determination of the molar heat capacities of the ternary compounds M2SexO3+2x (M = Bi, Y, Nd, Sm) and the comparison with theoretical derivatives are described. It is shown, how the functions of the binar
- Schmidt, Peer,Zhang-Presse, Mei,Oppermann, Heinrich
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p. 2665 - 2670
(2008/10/08)
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- The kinetics of isothermal decomposition of antimony and bismuth selenites
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The kinetics of isothermal decomposition of Sb2(SeO3)2 was studied in the temperature range 623-773 K. The decomposition products were (SbO)2SeO3, and SeO2. The activation energy, the frequency and steric factors, and the entropy, enthalpy, and Gibbs energy of formation of an activated complex from the reagent were determined. The numerical values of these parameters were compared with those for Bi2(SeO3)3. The thermal stability of selenites was found to correlate with the radius of the cation.
- Vlaev,Gospodinov,Genieva
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p. 1437 - 1440
(2007/10/03)
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- Study on the kinetics of the isothermal decomposition of selenites from IIIB group of the periodic system
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Both the thermal stability and the kinetics of the isothermal decompositions of the selenites of aluminium, gallium and indium have been studied. A relationship between the activation energy of the process and the radius of cations was found. Such a relationship is believed to result from the effect of counter-polarization of the selenite anion, that depends on the cation nature. The negative values of the activation entropy changes show that the active complex has a more complicated structure than the starting reactant. The increase of the observed absolute values of the activation entropy changes from indium to aluminium selenite also indicates that the structure of the active complex improves with the decrease of cation radius. The values of the steric factor calculated from the Arrhenius equation are significantly lower than unity which means that the isothermal decomposition of selenites from IIIB group of the periodic system belongs to the so-called slow reactions.
- Vlaev,Gospodinov
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- Effect of oxygen impurity on the optical transmission of As 2Se3.4 glass
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As2Se3.4 glass samples with controlled oxygen content in the range (1.4-7.9) × 10-2wt % were used to assess the effect of oxygen impurity on the IR absorption spectrum of the glass. The spectral dependence of the extinctio
- Churbanov,Shiryaev,Smetanin,Pimenov,Zaitseva,Kryukova,Plotnichenko
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p. 1188 - 1194
(2008/10/08)
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- Phase states of europium selenites in aqueous medium and in thermal analysis
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The solubility isotherm of the system Eu2O3-SeO2-H2O was studied at 100 °C. Certain amounts of the obtained selenites (normal and acid) were subjected to thermal analysis. The intermediate phases were isolated a
- Gospodinov,Stancheva
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p. 221 - 226
(2008/10/08)
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- Kinetics of the highly selective liquid-phase oxidation of side chain alkyl groups in 2-methylpyrazine and picolines by selenium dioxide
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Kinetics of the liquid-phase oxidation of alkyl groups in 2-methylpyrazine and picolines with selenium dioxide at moderate conditions were studied. Thus, 2-methylpyrazine was oxidized to pyrazinoic acid with selenium dioxide in pyridine at 115 °C with 99% selectivity at a 2-methylpyrazine conversion of 100% in 8 h. It was deduced that the reaction follows secondorder kinetics and the activation energy was found to be 35 kcal/mol. The same reaction-scheme was found to hold for picolines oxidation to obtain picolinic acids. The byproduct selenium, formed in the reaction, was converted back to selenium dioxide by nitric acid oxidation with 100% selectivity.
- Mukhopadhyay, Sudip,Chandalia, Sampatraj B.
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p. 455 - 459
(2013/09/08)
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- Antiparasitic marcfortines and paraherquamides
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The present invention includes various substituted marcfortines of the type exemplfied by the compounds of formula STR1 and paraherquamides which are useful as antiparasitic agents.
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- OXIDATION OF CADMIUM SELENIDE SULFIDE BY ATMOSPHERIC OXYGEN.
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The authors studied the kinetics of oxidation of cadmium selenide sulfide and its components by atmospheric oxygen. Specimens in the form of tablets pressed from powders were used for studying the oxidation rate. They also studied the course of oxidation of the pigment, CdS, CdSe, and mixtures of these components with powdered vitreous-enamel frit of the composition (mass %): 47 SiO//2, 9. 9 Al//2O//3, 14. 4 Na//2O, 3. 6 K//2O, 6. 4 CaO, 11. 8 B//2O//3, 7. 3 F at a uniform heating rate of 10 deg/min. It is shown that the main process during firing of enamel colored with CdS or selenium-cadmium pigment before the start of spreading is formation of CdSO//4. In the case of CdS the sulfate is formed on the surface, whereas in the case of the pigment CdSO//4 may also be formed within the volume of the latter. This must be taken into account in selection of the composition of the frit. It must be as fusible as possible, because sulfates have a harmful effect on the quality of colored enamels.
- Zupnik,Buler,Perminov,Setnik
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p. 2171 - 2173
(2008/10/08)
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- Vibrational spectra of trihaloselenate(IV) ions, SeOX3-
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Several trifluoro- and tribromoselenate(IV) compounds, MSeOF3 and MSeOBr3, have been made and characterized by IR and Raman spectroscopy. Comparison of the spectra with those of the trichloroselenate(IV) compounds previously reported has been made. In all cases the spectra are consistent with trigonal-bipyramidal stereochemistry predicted by valence-shell-electron-pair repulsions with the oxygen and lone electron pair equatorial. Anion polymerization via oxygen or halogen bridging is very weak for MSeOF3 (M = K, Cs) but becomes significant for MSeOCl3 where M = K and for MSeOBr3 where M = Me4N. Compounds with larger cations contain isolated SeOX3- anions. Normal-coordinate analysis has been used to assist in assigning the spectra. The force constants calculated show the equatorial halogen is more strongly bound to selenium than is the axial halogen.
- Milne, John,Lahaie, Pierre
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p. 2425 - 2428
(2008/10/08)
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- Recovery of selenium from copper anode slimes
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It is shown that the deselenization of decopperized slimes (obtained in copper refining) in an oxidizing atmosphere proceeds initially by the volatilization of the free selenium content at about 360 C. At higher temperatures,svrsnde is decomposed either directly or via the formation of silver selenite and its subsequent decomposition. It is also shown that the deselenization of pelletized slimes is feasible if a forced air flow is provided ovr the reacting particle.
- DUTTON WA,VAN DEN STEEN AJ,THEMELIS NJ
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p. 3091 - 3097
(2008/10/08)
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