Electroconductance of single-crystal Li2 + x Fe 2 − 2x 2+ Fe x 3+ (MoO4)3 (x = 0.22)

Electrophysical properties of single-crystal Li_{2 + x} Fe _{2 ? 2x} ²⁺ Fe _x ³⁺ (MoO₄)₃ (x = 0.22) are studied at 25–400°C. It is found that the conduction is of electronic nature and the conductivity equals 5 × 10^-2 S/cm at 300°C. The activation energy for the electron transport is 0.23 eV. The conductance in molybdate Li_2.22Fe _1.56 ²⁺ Fe _0.22 ³⁺ (MoO₄)₃ is markedly anisotropic.     

High-pressure synthesis and local structure of corundum-type In(2-2x)Zn(x)Sn(x)O(3) (x ≤ 0.7)

The corundum-type In(2-2x)Zn(x)Sn(x)O(3) solid solution (cor-ZITO, x ≤ 0.7) was synthesized at 1000 °C under a high pressure of 70 kbar. cor-ZITO is a high-pressure polymorph of the transparent conducting oxide bixbyite-In(2-2x)Zn(x)Sn(x)O(3) (x ≤ 0.4). Analysis of the extended X-ray absorption fine structure suggests that significant face-sharing of Zn and Sn octahedra occurs, as expected for the corundum structure type. In contrast to the ideal corundum structure, however, Zn and Sn are displaced and form oxygen bonds with lengths that are similar to those observed in high-pressure ZnSnO(3). Powder X-ray diffraction patterns of cor-ZITO showed the expected unit cell contraction with increased cosubstitution, but no evidence for ilmenite-type ordering of the substituted Zn and Sn. A qualitative second harmonic generation measurement, for the solid solution x = 0.6 and using 1064 nm radiation, showed that Zn and Sn adopt a polar LiNbO(3)-type arrangement.     

Formation of (C x H2x+1)4NBr·nH2O (x = 1–3) hydrate

The phase diagram of the binary system tetramethylammonium bromide-water was studied by the differential thermal analysis. In the stable region two phases, ice and the salt itself, were detected, and in the metastable region, three tetramethylammonium bromide hydrates (bromide-water, 1 : 4, mp 68.8°C, 1 : 5, mp 36.0°C, 1 : 7.5, mp ?19.5°C) were found. Formation of (C _x H_2x+1)₄NBr·nH₂O (x = 1–3, n = 4, 5, 7.5) hydrates was revealed.     

Synthesis and Ionic Conductivity of LiZr2(VO4)x(PO4)3 – x

Russian Journal of Electrochemistry - Vanadate phosphates LiZr2(VO4)x(PO4)3 – x are synthesized by the sol-gel technique with subsequent annealing and studied using X-ray diffraction...     

Synthesis of Calcium Phosphates by PO(OH)x(OBut)3−x and CaO2C2H4

In this work, an alkoxide solution route to synthesize Ca phosphates was developed. For the precursors, a CaO₂C₂H₄ solution was prepared by dissolving Ca metal powder into ethylene glycol, and a PO(OH)_x(OBut)_3–x solution was prepared by dissolving P₂O₅ inton -butanol under reflux conditions. In order to obtain a mixed solution of the two precursors, acetic acid was used as an additive. The experimental results show that (1) -2CaO · P₂O₅, -3CaO · P₂O₅, and hydroxyapatite can be easily synthesized by converting the corresponding mixed solutions to powder products in a hot plate, and calcining the as prepared products at 1100°C; (2) acetic acid behaves as a good agent for controlling the reactions between the two precursors by modifying the CaO₂C₂H₄ species in solution and decreasing the reactivity of the PO(OH)_x(OBut)_3–x species.     

Crystal structure of Ag2TeS3 and Na(Na1−x Ag x )TeS3 (x≈0.5) and the geometry of Te(IV)S3 polyhedra

Summary Structural data determined by single crystal X-ray experiments (T=300 K) are reported for Ag₂TeS₃ (monoclinic, Cc-C _s ⁴ ;a=6.783(1),b=11.567(2),c=7.693(1) Å; =114.44(1)°;Z=4;R=0.044) and for Na(Na_1–x Ag _x )TeS₃ x0.5; monoclinic, P2₁/c-C _2h ⁵ ;a=5.761(9),b=12.171(8),c=8.342(4) Å; =92.26(6)°;Z=4;R=0.030). In both compounds the atomic arrangements are characterized by isolated trigonal pyramidal TeS₃ polyhedra, irregularly coordinated Ag and Na atoms forming AgS₄ and (Na, Ag)S₄ polyhedra, and slightly distorted NaS₆ octahedra. Crystals of both compounds were synthesized under moderate hydrothermal conditions from an equimolar mixture of the elements in concentrated aqueous ammonia and 5N NaOH solution, respectively.

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Kristallstruktur von Ag₂TeS₃ und Na(Na_1–x Ag _x )TeS₃ (x0.5) nebst einem Vergleich der Geometrie von TeS₃-Gruppen

Zusammenfassung Es wird über die mittels Röntgenbeugungsexperimenten an Einkristallen bei 300 K bestimmten Strukturen von Ag₂TeS₃ (monoklin Cc-C _s ⁴ ;a=6.783(1),b=11.567(2),c=7.693(1) Å; =114.44(1)°;Z=4;R=0.044) und Na(Na_1–x Ag _x )TeS₃ (x0.5; monoklin, P2₁/c-C _2h ⁵ ;a=5.761(9),b=12.171(8),c=8.342(4)Å; =92.26(6)°;Z=4;R=0.030) berichtet. In beiden Verbindungen ist die Atomanordnung durch isolierte trigonal-pyramidale TeS₃-Polyeder, unregelmäßig koordinierte Ag- und Na-Atome, AgS₄- und (Na, Ag)S₄-Polyeder bildend, sowie leicht verzerrte NaS₆-Oktaeder charakterisiert. Kristalle der beiden Verbindungen wurden unter moderaten Hydrothermalbedingungen aus einem equimolaren Gemenge der Elemente und konzentrierter wäßriger Ammoniaklösung bzw. 5N NaOH-Lösung gezüchtet.

     

Atom Exchange Versus Reconstruction: (GexAs4−x)x− (x=2, 3) as Building Blocks for the Supertetrahedral Zintl Cluster [Au6(Ge3As)(Ge2As2)3]3−

The Zintl anion (Ge₂As₂)²⁻ represents an isostructural and isoelectronic binary counterpart of yellow arsenic, yet without being studied with the same intensity so far. Upon introducing [(PPh₃)AuMe] into the 1,2-diaminoethane (en) solution of (Ge₂As₂)²⁻, the heterometallic cluster anion [Au₆(Ge₃As)(Ge₂As₂)₃]³⁻ is obtained as its salt [K(crypt-222)]₃[Au₆(Ge₃As)(Ge₂As₂)₃]⋅en⋅2 tol ( 1 ). The anion represents a rare example of a superpolyhedral Zintl cluster, and it comprises the largest number of Au atoms relative to main group (semi)metal atoms in such clusters. The overall supertetrahedral structure is based on a (non-bonding) octahedron of six Au atoms that is face-capped by four (Ge_xAs_4−x)^x− (x=2, 3) units. The Au atoms bind to four main group atoms in a rectangular manner, and this way hold the four units together to form this unprecedented architecture. The presence of one (Ge₃As)³⁻ unit besides three (Ge₂As₂)²⁻ units as a consequence of an exchange reaction in solution was verified by detailed quantum chemical (DFT) calculations, which ruled out all other compositions besides [Au₆(Ge₃As)(Ge₂As₂)₃]³⁻. Reactions of the heavier homologues (Tt₂Pn₂)²⁻ (Tt=Sn, Pb; Pn=Sb, Bi) did not yield clusters corresponding to that in 1 , but dimers of ternary nine-vertex clusters, {[AuTt₅Pn₃]₂}⁴⁻ (in 2 – 4 ; Tt/Pn=Sn/Sb, Sn/Bi, Pb/Sb), since the underlying pseudo-tetrahedral units comprising heavier atoms do not tend to undergo the said exchange reactions as readily as (Ge₂As₂)²⁻, according to the DFT calculations.     

Phosphates M 0.5(1 + x) 2+ Cr x Ti2 − x (PO4)3: Synthesis, structure, and catalytic properties

Complex phosphates of titanium, chromium, and metals(2+) of the general formula M_{0.5(1 + x} )Cr _x Ti_{2 ? x} (PO₄)₃ (M = Mg, Ca, Mn, Ni, Sr, Ba, and Pb) were synthesized. Their phase formation was studied by means of X-ray powder diffraction, electron probe microanalysis, differential thermal analysis, and IR spectroscopy. Individual phases and solid solutions crystallizing in kosnarite and langbeinite structure types were identified; their crystallographic parameters were calculated. The catalytic properties of phosphates Ca_{0.5(1 + x} )Cr _x Ti_{2 ? x} (PO₄)₃ in methanol conversion were studied.     

Glycolate Ti1 − x Fe x (OCH2CH2O)2 − x/2 as a precursor for the preparation of quasi-one-dimensional (1D) solid solutions Ti1 − x Fe x O2 − 2x/2 (0 ≤ x ≤ 0.1)

Quasi-one-dimensional (1D) solid solutions Ti_{1 ? x} Fe _x (OCH₂CH₂O)_{2 ? x/2} (0 < x ≤ 0.1) with the structure of anatase were prepared by heating the glycolate Ti_{1 ? x} Fe _x (OCH₂CH₂O)_{2 ? x/2} in an atmosphere of air at a temperature of >450°C. The conditions of formation and the properties of the new glycolate Ti₃Fe₂(OCH₂CH₂O)₉ were described. It was found that the synthesized Ti_{1 ? x} Fe _x O_{2 ? 2x/2} solid solutions exhibit photocatalytic activity in the reaction of hydroquinone oxidation in an aqueous solution on irradiation with UV light. A correlation between the rate of oxidation of hydroquinone and the concentration of iron in the catalyst was established. A procedure for the preparation of titanium dioxide with the structure of anatase doped with iron and carbon (Ti_{1 ? x} Fe _x O_{(2 ? x/2) ? yCy)} and also composites on its basis, which contain an excess amount of carbon, was proposed.     

Synthesis and phase formation in M 0.5(1+x) 2+ FexTi2−x (PO4)3 phosphate series

New complex phosphates of titanium, iron, and alkaline-earth metals have been synthesized. X-ray powder diffraction, differential thermal analysis (DTA), and IR spectroscopy are used to study phase formation in the series of M_0.5(1+x)Fe_xTi_2?x (PO₄)₃ (M = Mg, Ca, Sr, Ba) phosphates. Individual compounds and solid solutions are found to crystallize in the NaZr₂(PO₄)₃ and K₂Mg₂(SO₄)₃ structure types. Their crystal parameters are calculated. CaFeTi(PO₄)₃ is studied using Mössbauer spectroscopy. Its structure is refined by the Rietveld method: space group $R\bar 3$ c, Z = 6, a = 8.5172(1), Å, c = 21.7739(4) Å, V = 1367.91(4) ų.     

Spin Crossover 1 A 1⇔ 5 T 2 in Solid Fe(trz)3x(atrz)3-3x(NO3)2·H2O (trz = 1,2,4-triazole, atrz = 4-amino-1,2,4-triazole)

The reaction of Fe(NO ₃ ) ₂ , trz, and atrz in ethanol–water gave solid Fe(trz) _3x (atrz) _3-3x (NO ₃ ) ₂ ·H ₂ O (x = 0.1, 0.2, 0.4, 0.8). The solids were investigated by magnetic chemistry, X-ray diffraction, photoelectron (DRS), IR, and Mössbauer spectroscopy methods. The individual Fe(trz)₃(NO₃)₂ and Fe(atrz)₃(NO₃)₂ as well as the solid phases exhibit a reversible spin crossover ¹ , whose temperature and character depend on the phase composition. Due to this, T _c may be changed by introducing another ligand into the complex exhibiting a spin crossover effect.     

Hydrates [Na2(H2O)x](2-thiobarbiturate)2 (x = 3, 4, 5): crystal structure,spectroscopic and thermal properties

The hydrates [Na₂(H₂O)₃(Htba)₂] (1) and [Na₂(H₂O)₄(Htba)₂] (2), where H₂tba is 2-thiobarbituric acid, were obtained under different thermal conditions from aqueous solutions and were structurally characterized. The molecular and supramolecular structures were compared to the known structure of [Na₂(H₂O)₅(Htba)₂] (3). In polymeric 1–3, the Htba^? ions are linked to Na⁺ through O and S forming octahedra. The decrease of the number of coordination water molecules led to an increase of the total number of bridge ligands (μ₂-H₂O, Htba^?) and a change of the Htba^? coordination. These factors induced higher distortion of the octahedra. It was assumed that hydrates, with a different number of coordinated water molecules, are more probable when the central metal has weaker bonds with O water molecules and with other ligands. The net topologies of 1–3 were compared. Thermal decomposition and IR spectra were analyzed for 1 and 2.     

Thermal properties and structure of (As2S3)100−x(Sb4S4)x glassy system

Thermal properties and structure of bulk glasses of (As₂S₃)_1?x(Sb₄S₄)_x system (x varies from 0 to 60 mol%) were studied by differential scanning calorimetry and Raman spectroscopy. It was found that with increasing Sb content the glasses can be sorted out to the three groups. The structure of glasses with x ≤ 10 is build-up mainly from AsS_3/2 pyramidal units and the well-known crystallization resistance of As₂S₃ can explain the reluctance of these undercooled liquids against crystallization. In glasses with a higher content of antimony, i.e., 10 < x ≤ 30 mol%, the vibration characteristics of As₄S₄ clusters appear. Undercooled melts of these glasses crystallize forming both β-As₄S₄ and high-temperature phases of Sb₂S₃. Structure of glasses with the highest antimony content (x > 30 mol%) is based on SbS_3/2 structural units significantly lowering stability of their undercooled melts from which only Sb₂S₃ crystallizes.     

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.     

Positron annihilation studies in YBa2Cu3O x (6<x≤7)

Positron lifetime and Doppler broadening of the annihilation line measurements, as a function of temperature between 14 and 300 K, have been performed on four YBa₂Cu₃O _x (6<x7) samples with different oxygen deficiency. It was found that the positron lifetime and theS parameter values increase as the oxygen deficiency increases in the YBa₂Cu₃O _x (6<x7) samples. It was also observed that the positron annihilation parameers show different temperature dependence in the YBa₂Cu₃O _x (6<x7) samples associated with their different oxygen deficiency.     

Sol-gel synthesis and structure of MZr2(AsO4)3 arsenates and MZr2(AsO4) x (PO4)3 − x arsenate phosphates (M = K,Rb, Cs)

MZr₂(AsO₄)₃ arsenates and MZr₂(AsO₄) _x (PO₄)_{3 ? x} arsenate phosphates (M = K, Rb, Cs) have been obtained by sol-gel synthesis followed by heat treatment and have been characterized by X-ray diffraction, electron probe microanalysis, and IR spectroscopy. Continuous series of substitutional solid solutions form in the MZr₂(AsO₄) _x (PO₄)_{3 ? x} systems (0 ≤ x ≤ 3). The solid solutions have a kosnarite structure (KZr₂(PO₄)₃, space group \(R\bar 3c\) ). The crystal structures of MZr₂(AsO₄)₃ and MZr₂(AsO₄)_1.5(PO₄)_1.5 have been refined by full-profile analysis. The structural frameworks of these phases are built from ZrO₆ octahedra and AsO₄ tetrahedra or (As,P)O₄ tetrahedra statistically populated by arsenic and phosphorus atoms. The alkali metal atoms occupy extraframework sites. The effect of the crystal chemical properties of alkali metals on the formation of the structures of MZr₂(AsO₄)₃ arsenates (M = Li-Cs) and MZr₂(AsO₄) _x (PO₄)_{3 ? x} solid solutions is discussed.     

Nd_(1 x)Ba_(2-x)Cu_3O_(7-δ)超导体的热处理

通过对Nd1 xBa2 -xCu3O7-δ的两种样品 (烧结样品和区域熔炼样品 )的XRD谱图分析 ,研究了高温氩气氛下热处理对样品中Nd对Ba的取代值x的影响 ,同时比较了不同样品的Tc 和Jc 值。研究表明 ,氩气下 95 0℃热处理可以减少Nd对Ba的取代 ,Tc 和Jc 都有不同程度的提高。对不同固溶度x值的Nd1 xBa2 -xCu3O7-δ进行吸氧热处理 ,样品在热处理前后分别作XRD分析。从XRD谱图可以看出 :当x <0 4时 ,样品经吸氧后可以从四方相转变为正交相 ,而当x >0 4时 ,样品虽经长时间吸氧也不能使其从四方相转变为正交相     

Structural and dynamical studies of δ-Bi2O3 oxide ion conductors: I. The structure of (Bi2O3)1−x(Y2O3)x as a function of x and temperature

We report the results of both Bragg and diffuse neutron scattering studies of the superionic solid solution, (Bi₂O₃)_1−x(Y₂O₃)_x. The Bragg data for polycrystalline samples show that the strutural features observed previously in (Bi₂O₃)_0.73(Y₂O₃)_0.27 are present across the entire range of the solid solution, 0.25 < x < 0.42. The number of 〈111〉-displaced anions in the defect fluorite structure decreases with increasing Y³⁺ content whereas the extent of short-range ordering on the anion sublattice increases. Both of these observations are consistent with the decrease in oxide ion conductivity which occurs as x increases. The basic crystal structure does not change between room temperature and 1023 K, although the unit cell volume increases by 3.78% for x = 0.27, and the number of 〈111〉-displaced anions increases, again consistent with the enhanced conductivity observed at high temperatures. It is suggested that Y³⁺ stabilizes the fluorite structure by ordering the vacancies on the oxygen sublattice in chains along the 〈111〉 and 〈110〉 directions.