Sodium ion-conducting solid electrolytes in the system Na3PO4Na2SO4

In the system Na₃PO₄Na₂SO₄, the high-temperature, cubic γ form of Na₃PO₄ forms an extensive range of solid solutions: Na_3−x(P_1−xS_x)O₄, 0 < x < (0.57 to 0.70, depending on temperature). For compositions in the range x = ca. 0.33 to 0.57, these γ solid solutions are thermodynamically stable at all temperatures. The conductivity of the γ solid solutions increases with increasing x and reaches a maximum at x = 0.5 to 0.6, with values of 2 × 10⁻⁵ ohm⁻¹ cm⁻¹ at 100°C, rising to 1.3 × 10⁻² ohm⁻¹ cm⁻¹ by 300°C; this conductivity increase with x is attributed to an increase in the sodium ion vacancy concentration, associated with the solid solution mechanism Na + PS. The phase diagram for the system Na₃PO₄Na₂SO₄ is given together with lattice parameters of the γ solid solutions.     

The electrochemical behaviour of polycrystalline silver electrodes in Na2CO3 solution and the effect of ClO− 4 ions

The electrochemical behaviour of polycrystalline silver electrodes in Na₂CO₃ solutions was studied under potentiodynamic and potentiostatic conditions and complemented with X-ray diffraction analysis. Potentiodynamic E/i anodic curves exhibit active passive transition prior to an oxygen evolution reaction. The active region involves a small peak AI followed by a major peak AII before the passive region. Peak AI is assigned to the formation of an Ag₂O layer while peak AII is due to the formation of an Ag₂CO₃ layer. The height of the anodic peaks increases with increasing Na₂CO₃ concentration, scan rate and temperature. The effect of increasing additions of NaClO₄ on the electrochemical behaviour of Ag in Na₂CO₃ solutions was investigated. The perchlorate ions stimulate the active dissolution of Ag, presumably as a result of the formation of soluble AgClO₄ salt. In the passive region, ClO⁻ ₄ ions tend to break down the dual passive film, leading to pitting corrosion at a certain critical pitting potential. The pitting potential decreases with ClO⁻ ₄ concentration. Potentiostatic current/time transients showed that the formation of Ag₂O and Ag₂CO₃ layers involves a nucleation and growth mechanism under diffusion control. However, in the presence of ClO⁻ ₄ ions, the incubation time for pit initiation decreases on increasing the anodic potential step. Received: 3 July 1998 / Accepted: 10 March 1999     

The structures of the solid solutions formed in the system (CrxFe1−x)VO4

Solid solutions (Cr_xFe_1−x)VO₄ can be prepared over a wide composition range and are thermally stable to above 900°C. They are isomorphous with α-MnMoO₄ rather than adopting the CrVO₄ or FeVO₄ structures. At 3000 atm pressure, a reversible transformation to a CrVO₄ type polymorph takes place. substitution of small amounts of phosphate into CrVO₄ also produces an α-MnMoO₄ isomorph.     

Sodium motion in the Nasicon related Na1+xZr2−xInx(PO4)3 solid solution: An NMR study

Sodium ion motion in Na_1+xZr_2−xIn_x(PO₄)₃ Nasicon-related materials (0 ≤ x ≤ 1.85) has been studied by NMR at two resonance frequencies from 170 to 450 K. At 8 MHz the resonance lines due to M1- and M2-type sites are well resolved. They are split by a strong second-order quadrupolar effect (ν_Q = 1.5 Megacycles (Mc)/sec). For NaZr₂(PO₄)₃ only the M1 site is occupied at RT, while a new site M5 appears at rising temperature (410 K). At 21 Mc/sec the line narrowing observed at increasing temperature illustrates the Na⁺ ion mobility within the skeleton. According to the temperature and the value of the ionic conductivity two diffusion mechanisms seem to occur.     

Potassium-conducting solid electrolytes in the K3 − 2x Cd x PO4 system

New potassium-conducting solid electrolytes of the K_{3 ? 2x} Cd _x PO₄ system are synthesized and studied. A wide range of solid solutions reaching x ≈ 0.35 with the structure of high-temperature modification of potassium orthophosphate forms in the system. An addition of cadmium ions leads to an abrupt increase in the K₃PO₄ conductivity due to the formation of potassium vacancies. The highest conductivity is approximately 10^?2 S cm^?1 at 300°C and above 10^?1 S cm^?1 at 700°C.     

Fe(III) extraction equilibria in the system: Fe2(SO4)3(NH4)2SO4 vs primene JM-T sulfate-toluene

Distribution coefficients for Fe(III) have been determined in the liquid-liquid extraction system Primene JM-T-toluene vs aqueous ammonium sulfate (and sodium sulfate) as a function of sulfate, acid, Fe(III) and amine sulfate concentrations. A study of loading equilibria as a function of time for this system indicates that equilibrium was largely achieved in 1 hr although some changes, possibly in the nature of the extracted species, occur up to approx. 20 hr. Extraction isotherms show a slope of 1 at low loadings, indicating the same degree of self association in both organic and aqueous phases, while the amine sulfate/iron ratio appears to approach 2.5 ± 0.25 at saturation loading. Results obtained by varying the sulfate concentration matrix indicates the formation of an aqueous complex of ferric ammonium sulfate which depresses iron distribution to the organic phase. The degree of aggregation of the amine sulfate, derived from iron distribution coefficient dependence on amine sulfate concentration data, is shown to be approx. 10.     

The state of metals in the supported bimetallic Pt−Pd/SO4/ZrO2 system

The behavior of the metals in the Pt−Pd/ZrO₂ and Pt−Pd/SO₄/ZrO₂ systems was studied by DRIFT spectroscopy. After reduction of Pt−Pd/ZrO₂ at 100 °C, the states of the metals are mainly Pt⁰ and Pd⁰ with a minor admixture of positively charged forms of Pt⁺ or Pd²⁺. An increase in the temperature of reduction leads to the formation of a bimetallic alloy. In the Pt−Pd/SO₄/ZrO₂ system, the effects of alloy formation and the interaction of the surface SO₄ groups superimpose. At low reduction temperatures, the surface SO₄ groups interact mainly with palladium. The influence of the surface sites on both supported metals increases with increasing reduction temperature. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1265–1270, July, 1999.     

The Raman spectra of tetracoordinate CdCl3X2− halogenocadmate(II) anions in the solid state

Anionic halogenocadmate(II) complexes of the type CdCl₃X²⁻ have been prepared and characterized as salts of tetrapropylammonium. The Raman spectra of these crystalline solids have been interpreted in terms of a C_3v symmetry. The tetrachlorocadmate(II) anion also possesses such a symmetry in the solid state.     

复盐K3Na(SO4)2的热化学研究

钾芒硝是一种成因复杂的复盐[1～ 3 ] ,并且由于钾芒硝Ｋ3 Ｎａ(ＳＯ4 ) 2 与硫酸钾石 [Ｋ3 Ｎａ(ＳＯ4 ) 2 或Ｎａ2 ＳＯ4 ·3Ｋ2 ＳＯ4 ]的化学组成相同 ,未能确定二者是否属于同一种复盐[4 ,5] 。我们合成了复盐Ｋ3 Ｎａ(ＳＯ4 )2[3 ] ,用溶解量热法测定了Ｋ3 Ｎａ(ＳＯ4 )2 和反应物 [Ｎａ2 ＳＯ4 (ｓ) +Ｋ2 ＳＯ4 (ｓ) ]的溶解焓 ,通过设计热化学循环计算出复盐的标准生成焓 ,为我们了解钾芒硝和硫酸钾石是否为同一复盐 ,并为进一步研究其成因和组成提供参考。1　实验部分1 1　试剂与仪器Ｋ2 ＳＯ4 (ｓ)和Ｎａ2 ＳＯ4 (ｓ)为Ａ .Ｒ .…     

Temperature dependence of the substrate selectivity in the hydroxylation of alkylbenzenes in the H2O2−H2SO4 system

The substrate selectivity in the hydroxylation of methylbenzenes in the H₂O₂−H₂SO₄ (70 wt.%) system was studied at 15–55 °C. The activation entropy correlates with the basicity of the arenes, while the substrate selectivity and activation enthalpy correspond both with the basicity and ionization potentials of ArH. We concluded that the structure of the reaction transition state is intermediate between a charge transfer complex and σ-complex. L. M. Litvinenko Institute of Physical Organic and Coal Chemistry, National Academy of Sciences of Ukraine, 70 R. Lyuksemburg ul., Donetsk 340114, Ukraine. Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 35, No. 1, pp. 39–43, January–February, 1999.     

ESR characterisation of SO−3 and SO−4 radicals in X-irradiated kainite (KMgClSO4.3H2O)

The ESR spectra of the kainite (KMgClSO₄.3H₂O) crystal revealed an intense isotropic (g = 2.004) peak C attributed to the SO⁻₃ radical and two pairs of lines (A₁, A₂) and (B₁, B₂) bearing intensity ratio 5:3. The intensity and linewidth variation of peak C suggested that the signal contains an unresolved shf structure. The power saturation studies on SO⁻₃ indicate that its ESR line is homogeneously broadened and its line shape is Lorentzian. The spin—lattice and spin—spin relaxation times (T₁ and T₂) of SO⁻₃ have been estimated to be 0.44 s and 656 μs, respectively. The analysis of the anisotropic pairs of lines show that they constitute two sets A and B and are due to two chemically inequivalent SO⁻₄ radical species in the lattice. The ESR spectra of the polycrystalline samples recorded at 300 and 77 K confirm the isotropic behaviour of SO⁻₃ and chemical inequivalence of two types of SO⁻₄ radicals. The principal g-values of the SO⁻₄ radical were evaluated to be: g₁ = 2.007, g₂ = 2.011, g₃ = 2.014 for species A and g₁ = 2.008, g₂ = 2.012, g₃ = 2.015 for species B. The low microsymmetry of the SO²⁻₄ ion in the lattice seems to promote the radiation damage.     

An investigation of the polythermal diagram of the H2ONa2HPO4Na2SO4 system

The polythermal diagram of the ternary system H₂ONa₂HPO₄Na₂SO₄ has been established, setting up nine isotherms obtained between 0 and 25°C by conductimetric analysis. The solubility domains of the various solid phases have been determined. One eutectic, three stable and one metastable transitional transformations have been observed. Temperature and composition of the eutectic point have been obtained by thermal analysis at constant flow.     

Phase equilibria of the Na,K,Mg,Ca//SO4,Cl-H2O system at 50°C in the crystallization range of glaserite 3K2SO4·Na2SO4

Phase equilibria of the Na,K,Mg,Na,K,Mg,Ca//SO₄,Cl-H₂O system are studied at 50°C via translation in the crystallization range of glaserite (3K₂SO₄ · Na₂SO₄). It is found that glaserite as the equilibrium phase of the investigated system at 50°C participates in the formation of 21 invariant points, 21 monovariant curves, and 34 divariant fields. A fragment of the phase equilibria diagram of the investigated system is constructed in the crystallization range of glaserite.     

Synthesis and characterization of the ZnxCd1−xIn2S4 pseudoternary solid solution

We have synthesized several compounds of the Zn_xCd_1−xIn₂S₄ family by solid phase reactions and chemical transport reactions using iodine. The reaction products have been characterized as to composition, structure, and lattice dynamics. Here we discuss and compare the different results obtained by the two synthesis methods.     

Kinetics, substrate selectivity and mechanisms of the first step in the oxidation of alkylbenzenes in the HVO3−H2SO4 system

The kinetics, kinetic isotope effects, and substrate selectivity were studied for the oxidation of alkylbenzenes in the HVO₃−H₂SO₄ system at 30°C. The reaction proceeds by an electrophilic substitution mechanism through a slow step involving formation of a charge transfer complex between the arene and VO ₂ ⁺ cation and is similar to nitration by the NO ₂ ⁺ cation. L. M. Litvinenko Institute of Physical Organic and Coal Chemistry, National Academy of Sciences of Ukraine, 70 R. Lyuksemburg ul., Donetsk 340114, Ukraine. Translated from Teoreticheskaya i éksperimental'naya Khimiya, Vol. 35, No. 6, pp. 349–353, November–December, 1999.     

A study of the thermal analysis of the solid solution (AgxK1−xNO3

The effect of partial replacement of K⁺ by Ag⁺ in the mixed system of KNO₃ and AgNO₃ during a set of DSC heating cycles was studied by means of a modern computerized DSC system. Thermal analysis was performed in the vicinity of the phase transition II I for pure KNO₃. The results revealed a large change in enthalpy and the phase transition temperature close to the morphotropic boundary x=0.5–0.6. At this boundary, the transformation enthalpy reached the maximum value of 101 J g^–1. On the basis of the data obtained from this accurate thermal analysis work, a model is suggested for the energy barrier of rotation of the nitrate ion in the mixed nitrate system.     

Phase equilibria in the system Rb3PO4–Ba3(PO4)2

The system Rb₃PO₄–Ba₃(PO₄)₂ was investigated by thermoanalytical methods, X-ray powder diffraction, ICP, and FT-IR. On the basis of the obtained results its phase diagram was proposed. For this system with one intermediate compound, BaRbPO₄, we found that this compound melts congruently at 1700 °C, exhibits a polymorphic transition at 1195 °C and is high-temperature unstable. Also, the intermediate compound was subject to gradual decomposes to Ba₃(PO₄)₂ (the solid phase) and vaporization (with conversion of phosphorus and rubidium oxides into vapor phase). We also found that Rb₃PO₄ melts congruently at 1450 °C and shows a polymorphic transition at 1040 °C. Regarding Ba₃(PO₄)₂, we have confirmed that it melts congruently at 1605 °C and exhibits a polymorphic transition at 1360 °C.     

Thermochemical investigations of the systems KCl−KBr−H2O,K2SO4−(NH4)2SO4−H2O and KNO3−NH4NO3−H2O at 298.15 K

For the equilibrium solid phases occurring in the systems: KCl?KBr?H₂O, K₂SO₄?(NH₄)₂SO₄?H₂O and KNO₃?NH₄NO₃?H₂O, the concentration dependencies of differential solution enthalpies, Δ_sol H ₂ for several crystallization paths, were measured. The limiting differential solution enthalpies, Δ_sol H ₂ ⁰ , were determined by extrapolation of the above dependencies to the ionic strength,I _m ⁰ , corresponding to the appropriate binary solutions. For KCl?KBr?H₂O system only, the clear dependence between Δ_sol H ₂ ⁰ andI _m ⁰ values was found and discussed.     

The formation of the Ba(CuOx)1−y(CO3)y

Carbocuprate compounds are generally described as multiple perovskites with CO ₃ ² - and Cu-O alternating layers containing Ba and/or Sr; they have gained an unexpected importance in the high temperature superconductivity field, because many compounds with transition temperature above 100 K belong to this class of materials.We have started a systematic study on phase formation and stabilisation in the Ba-Cu-C-O system in the temperature range 20-600°C, by using thermal analysis techniques. Starting from a BaCO₃-BaO₂-CuO mixture (311 mol), a new phase isomorphic with BaCO₃ formed after heat treatment above 390°C in air. TG, DSC, EGA and high temperature XRD were employed to follow the complex interaction of the reactants with the atmosphere and the formation of the new phase.