Preparation and crystal structure of members of the solid solution phase Ba5Ru2−xAl1+x−yCuyO11 with x=0.378, y=0.085 and x=0.5, y=0

Single crystals of the new phase Ba₅Ru_2−xAl_1+x−yCu_yO₁₁ (x=0.378, y=0.085) have been grown from a powder mixture of BaCO₃, RuO₂ and CuO in an alumina crucible. The new compound crystallizes isostructurally to Ba₅Ir₂AlO₁₁. The crystal structure was determined by X-ray single-crystal diffraction technique and refined to a composition of Ba₅Ru_1.622(8)Al_1.29(1)Cu_0.085(6)O₁₁ (orthorhombic, Pnma (No. 62), a=18.615(4) Å, b=5.771(1) Å, c=11.098(2) Å, Z=4, R₁=0.048, wR₂=0.075). The composition of the new compound obtained from crystal structure refinement is in good agreement with the result of electron probe microanalysis using wavelength-dispersive X-ray spectroscopy. Octahedra [RuO₆] are connected via faces forming pairs. The central positions of the octahedra pairs are statistically occupied by Ru and Al atoms. These octahedra pairs are interconnected to one-dimensional chains extending along [010] via tetrahedra [Al_1−yCu_yO₄]. Isotypic Ba₅Ru_1.5Al_1.5O₁₁ is a further member of the solid solution with the lattice parameters a=18.6654(5) Å, b=5.7736(1) Å, c=11.0693(3) Å according to Rietveld refinement on a microcrystalline sample.     

Mechanical properties of mixed conducting La0.5Sr0.5Fe1−x Co x O3−δ (0≤x≤1) materials

Young’s modulus, strain–stress behavior, fracture strength, and fracture toughness of (0≤×≤1) materials have been investigated in the temperature range 20–1,000°C. Young’s moduli of and , measured by resonant ultrasound spectroscopy, were 130±1 and 133±3 GPa, respectively. The nonlinear stress–strain relationship observed by four-point bending at room temperature was inferred as a signature of ferroelastic behavior of the materials. Above the ferroelastic to paraelastic transition temperature, the materials showed elastic behavior, but due to high-temperature creep, a nonelastic respond reappeared above ∼800°C. The room temperature fracture strength measured by four-point bending was in the range 107–128 MPa. The corresponding fracture toughness of , measured by single edge V-notch beam method, was 1.16±0.12 MPa·m^1/2. The measured fracture strength and fracture toughness were observed to increase with increasing temperature. The fracture mode changed from intragranular at low temperature to intergranular at high temperature. Tensile stress gradient at the surface of the materials caused by a frozen-in gradient in the oxygen content during cooling was proposed to explain the low ambient temperature fracture strength and toughness.     

Oxygen transport in La0.5Sr0.5Fe1−yTiyO3−δ (y=0.0, 0.2) membranes

The influence of partial substitution of Fe with Ti on the oxygen transport properties of La_1−x Sr _x FeO₃ membranes was investigated in view of their application for oxygen separation. Samples of composition (y=0, 0.2) were prepared and their oxygen transport properties characterised by potential step relaxation and by oxygen permeation measurement in an air/argon gradient. With the first technique, chemical diffusion and surface exchange (k _S) coefficients were obtained by fitting of the current relaxation data to a single expression valid over the complete time range. The Ti-substituted composition gave slightly larger values of and k _S. The trend was opposite for the measured oxygen permeation flux. In the latter experience, ordering of oxygen vacancies was observed at lower temperature, reducing significantly the performance of the material.     

NxHy-Fe(x=0～2,y=0～3)配位簇的DFT计算

采用杂化密度泛函（DFT）之B3LYP/6-311G**方法研究了NxHy-Fe(x=0～2,y=0～3)配位簇的几何结构和振动光谱。讨论了在纯铁催化剂上,氮分子和氢分子逐步合成氨的反应机理。结果表明,合成氨过程可能经历N2和N2H2物种。在优化结构的基础上,计算了各个模型的振动频率并解释了有关实验结果。     

Electrical, electrochemical, and thermomechanical properties of perovskite-type (La1?x Sr x )1?y Mn0.5Ti0.5O3?δ (x?=?0.15–0.75, y?=?0–0.05)

Strontium additions in (La_1?x Sr _x )_1?y Mn_0.5Ti_0.5O_3?δ (x?=?0.15–0.75, y?=?0–0.05) having a rhombohedrally distorted perovskite structure under oxidizing conditions lead to the unit cell volume contraction, whilst the total conductivity, thermal and chemical expansion, and steady-state oxygen permeation limited by surface exchange increase with increasing x. The oxygen partial pressure dependencies of the conductivity and Seebeck coefficient studied at 973–1223?K in the p(O₂) range from 10^?19 to 0.5?atm suggest a dominant role of electron hole hopping and relatively stable Mn³⁺ and Ti⁴⁺ states. Due to low oxygen nonstoichiometry essentially constant in oxidizing and moderately reducing environments and to strong coulombic interaction between Ti⁴⁺ cations and oxygen anions, the tracer diffusion coefficients measured by the ¹⁸O/¹⁶O isotopic exchange depth profile method with time-of-flight secondary-ion mass spectrometric analysis are lower compared to lanthanum–strontium manganites. The average thermal expansion coefficients determined by controlled-atmosphere dilatometry vary in the range 9.8–15.0?×?10^?6?K^?1 at 300–1370?K and oxygen pressures from 10^?21 to 0.21?atm. The anodic overpotentials of porous La_0.5Sr_0.5Mn_0.5Ti_0.5O_3?δ electrodes with Ce_0.8Gd_0.2O_2-δ interlayers, applied onto LaGaO₃-based solid electrolyte, are lower compared to (La_0.75Sr_0.25)_0.95Cr_0.5Mn_0.5O_3?δ when no metallic current-collecting layers are introduced. However, the polarization resistance is still high, ~2 Ω?×?cm² in humidified 10?% H₂–90?% N₂ atmosphere at 1073?K, in correlation with relatively low electronic conduction and isotopic exchange rates. The presence of H₂S traces in H₂-containing gas mixtures did not result in detectable decomposition of the perovskite phases.     

Hydrogen content in proton-conducting perovskites CaZr1 − x Sc x O3 − x /2 (x = 0.0–0.2)

The hydrogen content in CaZr_{1 ? x} Sc _x O_{3 ? x/2} (x = 0.00–0.20) and BaZr_0.9Y_0.1O_3-α (for comparison) was studied by powder nuclear microanalysis. The samples were saturated with heavy water (D₂O) vapors at 350 and 400°C in air. The chemical expansion of the CaZr_0.95Sc_0.05O_3-α and BaZr_0.95Y_0.05O_3-α samples at 700°C was measured at different water vapor pressures. A model was suggested to explain the lowered hydrogen content in oxides based on CaZrO₃.     

Global Minimum Search and Bonding Analysis of Tl2Hx and Tl3Hy (x=0–6; y=0–5) Series

A remarkable distinction between boron and carbon hydrides lies in their extremely different bonding patterns and chemical reactivity, resulting in diverse areas of application. Particularly, carbon, characterized by classical two-center – two-electron bonds, gives rise to organic chemistry. In contrast, boron forms numerous exotic and non-intuitive compounds collectively called non-classical structures. It is reasonable to anticipate that other elements of Group 13 exhibit their own unusual bonding patterns; however, our knowledge of the hydride chemistry for other elements in Group 13 is much more limited, especially for the heaviest stable element, thallium. In this work, we performed a conformational analysis of Tl₂H_x and Tl₃H_y (x=0–6, y=0–5) series via Coalescence Kick global minimum search algorithm, DFT, and ab initio quantum chemistry methods; we investigated the bonding pattern using the AdNDP algorithm, thermodynamic stability, and stability toward electron detachment. All found global minimum structures are classified as non-classical structures featuring at least one multi-center bond.     

Determination of the stability constants of Pb–(DIPSO)x–(OH)y and Pb–(AMPSO)x–(OH)y systems

In this work, complexation between lead ion and the ligands 3-[N,N-bis(2-hydroxyethyl)amino]-2-hydroxypropanesulfonic acid (DIPSO) and N-(1,1-dimethyl-2-hydroxyethyl)-3-amino-2-hydroxypropanesulfonic acid (AMPSO), which are commercial pH buffers, is presented. Both ligands form complexes with lead in their pH buffer range (between pH 6.5 and 8.5 for DIPSO and between pH 8.0 and 9.0 for AMPSO). The final models and the overall stability constants, which are reported here, were determined by direct current polarography and glass electrode potentiometry [only for the Pb–(DIPSO)_x–(OH)_y system] at 25.0 °C and 0.1 M KNO₃ ionic strength. For the Pb–(DIPSO)_x–(OH)_y system, the proposed final model contains PbL, PbL₂, PbL₂(OH), and PbL₂(OH)₂ with stability constants, as log β, of 3.4 ± 0.1, 6.35 ± 0.15, 12.8 ± 0.2, and 18.0 ± 0.3, respectively. For the Pb–(AMPSO)_x–(OH)_y system, the species observed are PbL, PbL(OH), and PbL(OH)₂ with stability constants, as log β, of 2.9 ± 0.5, 9.4 ± 0.1, and 14.5 ± 0.2, respectively. For AMPSO, the possible adsorption of the ligand at the mercury electrode surface was evaluated by alternating current polarography through calculation of the capacitance of the double layer.     

Electroconductivity and nature of ion transfer in La1 − x Sr x Sc1 − y Mg y O3 − α system (0.01 ≤ x = y ≤ 0.20) in dry and humid air

The conductivity and ion and proton transfer numbers were measured in La_{1 ? x} Sr _x Sc_{1 ? y} Mg _y O_{3 ? α} system (x = y = 0.10–0.20). The partial conductivities (total ion, proton, oxygen, hole) and their effective activation energies were calculated. The measurements were carried out in air with respect to humidity (pH₂O = 0.04?2.65 kPa) within the temperature range from 630 to 920°C.     

Phase Transitions in the BaCe1–x Nd x O3–δ System (x = 0–0.15)

Phase transitions in BaCe_{1 – x} Nd _x O_3– (x = 0–0.15) are studied on ceramic samples by dilatometry (at 370–1100 K) and by measuring electroconductivity (at 750–1220 K). Ion transport numbers are measured by an EMF method at 850–1240 K. All measurements are done in dry air (₂ 40 Pa). By treating the obtained temperature dependences of linear expansion with a difference method (difference between first-degree polynomial approximating the dependence and experimental points), the position and the sort of the phase transitions are determined. High-temperature phase transitions are confirmed by measuring the electroconductivity and ion transport numbers. Second-order phase transitions in pure BaCeO₃ are discovered at 480 ± 10, 530 ± 10, 900 ± 10, 1030 ± 20, and 1170 ± 10 K and a first-order transition, at 665 ±10 K. Phase transitions at 900 and 1030 K are discovered for the first time ever.     

Synthesis and crystal structure of Mo6−x Nb x I11 (x = 1–1.5)

A solid solution Mo_{6 ? x} Nb _x I₁₁ (x = 1.1–1.5) containing cluster cores {Mo₅NbI₈} is obtained by the high-temperature reaction of molybdenum, niobium, and iodine (550°C, 70 h, quartz ampule). According to the X-ray diffraction data, heating at 800°C in a molybdenum container results in the decomposition of the solution to Mo₆I₁₂ and Nb₆I₁₁. According to the X-ray structure analysis data, the compounds are isostructural to the high-spin modification Nb₆I₁₁ (space group Pccn). The presence of Nb atoms in the structure changes the structural type from the layered (Mo₆I₁₂) to framework structure, noticeably increases the metalmetal distances (2.661–2.716 Å, 2.695 Å) Mo₆ octahedron with the retention of the distance from the metal (M) to the μ₃-“capped” I atoms, and strongly elongates the M₆-I-M₆ bridges almost to the value observed in Nb₆I₁₁.     

Synthesis and magnetic properties of Cu0.5Fe0.5 ? x In x Cr2S4 (x = 0?0.4) solid solutions

Multistep synthesis with X-ray diffraction monitoring of the phase composition has been carried out, optimal synthesis parameters have been determined, and the magnetic properties of solid solutions between thiospinels with ordered tetrahedral A lattices (ferrimagnet Cu_0.5Fe_0.5Cr₂S₄ (T _C = 347 K) and anti-ferromagnet Cu_0.5In_0.5Cr₂S₄ (T _N = 35 K) have been studied. Both compounds crystallize in F $\bar 4$ 3m (T _d ² ) structure. Measurements over wide ranges of fields (0.05?C40 kOe) and temperatures (5?C300 K) highlighted the nature of magnetism in the samples; new magnetic species have been discovered.     

Novel red-emitting phosphors, (Mg(1−x−y)MnxDyy)Al2Si2O8 and (Mg(1−x−y)MnxTmy)Al2Si2O8

Mn⁴⁺ doped and Dy³⁺, Tm³⁺ co-doped MgAl₂Si₂O₈-based phosphors were prepared by conventional solid state reaction at 1,300 °C. They were characterized by thermogravimetry, differential thermal analysis, X-ray powder diffraction, photoluminescence, and scanning electron microscopy. The luminescence mechanism of the phosphors, which showed broad red emission bands in the range of 600–715 nm and had a different maximum intensity when activated by UV illumination, was discussed. Such a red emission can be attributed to the ²E → ⁴A₂ transitions of Mn⁴⁺.     

Synthesis and characterization of a NASICON phase of variable composition Na1 − x Ni1 − x Sc1 + x (MoO4)3 (0 ≤ x ≤ 0.5)

Subsolidus phase ratios in the Na₂MoO₄-NiMoO₄-Sc₂(MoO₄)₃ system have been studied using X-ray diffraction, differential thermal analysis, and vibrational spectroscopy. A phase of variable composition Na_{1 ? x} Ni_{1 ? x} Sc_{1 + x} (MoO₄)₃ (0 ≤ x ≤ 0.5) having NASICON structure (space group \(R\bar 3c\) ) and a triple molybdate crystallizing in triclinic system (space group \(P\bar 1\) ) have been obtained. The high conductivity of Na_{1 ? x} Ni_{1 ? x} Sc_{1 + x} (MoO₄)₃ allows the phase of variable composition to be regarded as a promising sodiumion-conductive solid electrolyte.     

Synthesis and Properties of Colored Copper-Containing Apatites of Composition Ca5(PO4)3CuyO y + δ(OH)0.5 − y − δX0.5 (X = OH,F, Cl)

Ca₅(PO₄)₃Cu_yO _{y + δ}(OH)_{0.5 ? y ? δ}X_0.5 compounds (for X = OH, y = 0.01–0.3; for X = F, y = 0.01–0.1; for X = Cl, y = 0.1) have been synthesized by heat treatment of oxide-carbonate mixtures at 1150°C in air and have been characterized by X-ray diffraction, electronic spectroscopy, and magnetic measurements. The compounds have an apatite structure in which copper atoms substitute for part of the hydroxyl hydrogen atoms in hexagonal channels. The electronic spectrum shows two main absorption bands due to d-d transitions in copper(II) linearly coordinated to two oxygen atoms, as well as extra, weaker bands, whose contribution to the overall spectrum decreases with decreasing y. The latter are assignable to copper atoms occupying other sites in the crystal lattice. The temperature dependence of the magnetic susceptibility of the compounds obeys the Curie-Weiss law with a Curie constant close to zero. The Weiss constant characterizes the copper(II) content of the compounds and correlates qualitatively with the intensity of the main absorption bands in the visible spectrum. The fraction of copper(II) in the total amount of copper in the apatites increases in the substituent order X: Cl, OH, F, as well as upon the low-temperature annealing of the compounds in air. At the same time, copper(II) fraction depends only slightly on the total copper content. As the copper(II) content increases, the color of apatite changes from pink to dark claret.     

Forms of oxygen in La1 − x Ca x MnO3 + δ (x = 0–1) perovskites and their reactivities in oxidation reactions

The effects of substitution in the cationic sublattice and of the synthesis procedure on the reactivity of different forms of oxygen in La_{1 ? x} Ca _x MnO_{3 + δ} perovskites synthesized by mechanochemical and ceramic processing was studied by temperature-programmed reduction (TPR) with hydrogen. As the calcium content of the perovskite is raised, the maxima of the TPR peaks shift to lower temperatures and the extent of reduction of the perovskite increase, implying an increase in the reactivity of the system. Conversely, raising the calcination temperature or extending the calcination time shifts the maxima of the peaks to higher temperatures and diminishes the extent of reduction of the sample. TPR data for the intermediate-composition samples can be explained in terms of the dependence of microstructure on the synthesis procedure (near-surface calcium segregation in the mechanochemically synthesized samples and the microheterogeneous structure of the ceramic samples). The reduction process Mn⁴⁺ → Mn²⁺ takes place in the low- and medium-temperature regions. According to the literature, the bulk reduction process Mn³⁺ → Mn²⁺ occurs at high temperatures. The activity of the system in CO oxidation is correlated with the amount of the most reactive surface oxygen, which is eliminated in hydrogen TPR runs below 250–300°C.     

Vibrational spectra and electrophysical properties of a NASICON phase of variable composition Na1 − x Co1 − x Sc1 + x (MoO4)3 (0 ≤ x ≤ 0.5)

Subsolidus phase ratios of the Na₂MoO₄-CoMoO₄-Sc₂(MoO₄)₃ system have been studied by X-ray diffraction, differential thermal analysis, and vibrational spectroscopy. A phase of variable composition Na_{1 ? x} Co_{1 ? x} Sc_{1 + x} (MoO₄)₃, 0 ≤ x ≤ 0.5 having NASICON structure (space group \(R\bar 3c\) ) and triple molybdate NaCo₃Sc(MoO₄)₅ crystallizing in triclinic system (space group \(P\bar 1\) ) have been obtained. The high conductivity of Na_{1 ? x} Co_{1 ? x} Sc_{1 + x} (MoO₄)₃ allows the phase of variable composition to be regarded as a promising sodium-ion conducting solid electrolyte.     

The electronic structure and properties of Ni1−xLixO1−y (0⩽x⩽1/4, 0⩽y⩽1/8)

The electronic structures of NiO, Ni_0.875O, NiO_0.875, Ni_0.875Li_0.125O, Ni_0.875Li_0.125O_0.875 and Ni_0.75Li_0.25O_0.875 with a NaCl-type crystal structure have been calculated using the ab initio linear muffin-tin orbitals method in the LSDA+U approximation. The effect of vacancies in the metal and metalloid sublattices and lithium ions on parameters of the NiO electronic spectrum (the energy gap and the valence band widths, etc.) has been analyzed. It is shown that the defects like the dipole LiV_O and the tripole LiV_OLi impaired stability and could reduce electrical conductivity of the nickel–oxide-based phases.     

Magnetic properties of (Cu0.5Ga0.5)1 − x Fe x Cr2S4 solid solutions

Magnetic properties are studied and a magnetic phase diagram is constructed for (Cu_0.5Ga_0.5)_{1 ? x} Fe _x Cr₂S₄ solid solutions formed between chromium chalcogenide spinels (Cu_0.5Ga_0.5)Cr₂S₄ and FeCr₂S₄.