Electroconduction of Solid Solutions Na3 – 2x M x PO4(M = Cd, Pb)

In the sodium-orthophosphate-based solid solutions in Na_{3 – 2x} M _x PO₄ systems (M = Cd, Pb), the electroconduction is maximum near the upper concentration boundaries of the single-phase regions: x 0.4 for M = Cd and x 0.25 for M = Pb. The conductivity values at 300°C are 6.25 × 10^–3 and 2.5 × 10^–3 S/cm, respectively. The conduction of synthesized solid electrolytes has a co-cation nature. Their electric characteristics, inferior to those of the Na₃PO₄-based solid solutions obtained via heterovalent substitutions of another type, may be a manifestation of an effect similar to the polyalkali effect.     

Electroconductivity of Solid Solutions Cs3–2x M x PO4 (M = Ba, Sr, Ca, Mg)

Solid solutions Cs_{3 – 2x} M _x PO₄ (M = Ba, Sr, Ca, Mg) are synthesized and their thermal behavior and electroconductivity are examined. Adding elements of Subgroup IIA of the periodic table into cesium orthophosphate shifts the phase transition, which occurs in pure Cs₃PO₄ at 450–620°, towards lower temperatures and raises the cesium cation conductivity at low temperatures. The electroconductivity of a high-temperature modification of Cs₃PO₄ is weakly dependent on the presence and concentration of such additives, which points to structural disordering of the cesium sublattice.     

[M(dap)3]2(Sb2Se5)·xH2O(M=Ni,x=2;M=Zn,x=0)的溶剂热合成及晶体结构

利用溶剂热法合成了2种新的有机杂化锑硒化合物[Ni(dap)3]2(Sb2Se5)].2H2O(1)和[Zn(dap)3]2(Sb2Se5)](2)(dap=1,2-丙二胺),单晶X射线衍射分析结果表明,1属于三方晶系,P3121空间群,晶胞参数为a=10.7574(14),b=10.7574(14),c=31.672(4),γ=120.00°,z=4。2属于单斜晶系,P21空间群,晶胞参数为a=10.772(2),b=16.391(3),c=11.704(2),β=100.912(4)°,z=4。在2种化合物中,Ni2 与Zn2 离子分别与3个dap配体螯合形成畸变八面体几何构型,其中dap配体的N原子是无序的,而二聚[Sb2Se5]2-阴离子是由2个SbSe3三角锥共用1个Se原子连接而成。     

Electroconductivity of Solid Electrolytes in the Systems K3–2x M x PO4 (M = Ca, Sr, Ba)

Solid electrolytes K_{3 – 2x} M _x PO₄ (M = Ca, Sr, Ba) are synthesized and the temperature and concentration dependences of their electroconductivity are studied. Adding calcium and strontium stabilizes the high-temperature -form of K₃PO₄ at room temperature, while barium-containing solid electrolytes undergo an eutectoid decomposition below 430°C. Maximum electroconductivity is exhibited by K_{3 – 2x} Sr _x PO₄ (7.1 × 10^–3 and 1.25 × 10^–1 S cm^–1 at 300 and 700°C).     

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.     

Solid potassium-conducting electrolytes in the K2 − 2x Ga2 − x V x O4 system

New potassium-conducting solid electrolytes based on potassium monogallate in the K_2?2x Ga_2?x V _x O₄ system are synthesized and studied. It is found that an introduction of V⁵⁺ ions leads to a considerable increase in the KGaO₂ conductivity due to the formation of vacancies in the potassium sublattice. The conductivity for optimal compositions is approximately 10^?3 S cm^?1 at 400°C and above 10^?2 S cm^?1 at 700°C. The results are compared with early obtained data for potassium monogallate dopped with four-charged cations.     

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.     

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.     

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.     

Electrochemical studies of LiCr x Fe x Mn2?2x O4 in an aqueous electrolyte

In this paper, LiCr _x Fe _x Mn_2−2x O₄ (x = 0, 0.05, 0.1) electrode materials were prepared by sol–gel technique and characterized by X-ray diffraction (XRD) and transmission electron microscopy or high-resolution transmission electron microscopy techniques. XRD results reveal that the Cr–Fe-co-doped LiCr _x Fe _x Mn_2−2x O₄ materials are phase-pure spinels. The electrochemical properties of the LiMn₂O₄, LiCr_0.05Fe_0.05Mn_1.9O₄, and LiCr_0.1Fe_0.1Mn_1.8O₄ electrodes in 5 M LiNO₃ aqueous electrolyte were investigated using cyclic voltammetry, AC impedance, and galvanostatic charge/discharge methods. In the current range of 0.5–2 A g⁻¹, the specific capacity of the LiCr_0.05Fe_0.05Mn_1.9O₄ electrode is close to that of the LiMn₂O₄ electrode, but the specific capacity of the LiCr_0.1Fe_0.1Mn_1.8O₄ electrode is obviously lower than that of the LiMn₂O₄ electrode. When the electrodes are charge/discharge-cycled at the high current rate of 2 A g⁻¹, the LiCr_0.05Fe_0.05Mn_1.9O₄ electrode exhibits an initial specific capacity close to that of the LiMn₂O₄ electrode, but its cycling stability is obviously prior to that of the LiMn₂O₄ electrode.     

Homoleptic diphosphacyclobutadiene complexes [M(η(4)-P2C2R2)2]x- (M = Fe, Co; x = 0, 1)

The preparation and comprehensive characterization of a series of homoleptic sandwich complexes containing diphosphacyclobutadiene ligands are reported. Compounds [K([18]crown-6)(thf)(2)][Fe(η(4)-P(2)C(2)tBu(2))(2)] (K1), [K([18]crown-6)(thf)(2)][Co(η(4)-P(2)C(2)tBu(2))(2)] (K2), and [K([18]crown-6)(thf)(2)][Co(η(4)-P(2)C(2)Ad(2))(2)] (K3, Ad = adamantyl) were obtained from reactions of [K([18]crown-6)(thf)(2)][M(η(4)-C(14)H(10))(2)] (M = Fe, Co) with tBuC[triple bond]P (1, 2), or with AdC[triple bond]P (3). Neutral sandwiches [M(η(4)-P(2)C(2)tBu(2))(2)] (4: M = Fe 5: M = Co) were obtained by oxidizing 1 and 2 with [Cp(2)Fe]PF(6). Cyclic voltammetry and spectro-electrochemistry indicate that the two [M(η(4)-P(2)C(2)tBu(2))(2)](-)/[M(η(4)-P(2)C(2)tBu(2))(2)] moieties can be reversibly interconverted by one electron oxidation and reduction, respectively. Complexes 1-5 were characterized by multinuclear NMR, EPR (1 and 5), UV/Vis, and M?ssbauer spectroscopies (1 and 4), mass spectrometry (4 and 5), and microanalysis (1-3). The molecular structures of 1-5 were determined by using X-ray crystallography. Essentially D(2d)-symmetric structures were found for all five complexes, which show the two 1,3-diphosphacyclobutadiene rings in a staggered orientation. Density functional theory calculations revealed the importance of covalent metal-ligand π bonding in 1-5. Possible oxidation state assignments for the metal ions are discussed.     

Study of ceramic pigments based on Er2Ce2?x Mo x O7

This contribution is focused on the synthesis, characterization and optical properties of new inorganic pigments which are environment friendly and can substitute some toxic metals in interesting colour compounds. Pyrochlores belong to the group of high-temperature pigments, and are a variety of actual and potential applications for several materials. Examples include catalysts, thermal barrier coatings, solid electrolytes, nuclear waste forms and host materials for luminescence centers. The pigments were prepared by the solid state reaction and also by method of suspension mixing of materials in the series with increasing content of molybdenum. The pigments were applied into organic matrix and ceramic glaze. The colour properties of these applications were investigated depending on content of Mo, method of preparation and temperature of calcination (1350?C1550?°C after step 50?°C). The optimum conditions for their synthesis were determined. The pigments were evaluated from standpoint of their structure, colour and particle sizes. Characterization of Er₂Ce_2?x Mo _x O₇ pigments (x?=?0.1, 0.3, 0.5 and 0.7) suggests that they have a potential to be alternative yellow or orange colourants for paints, plastics, ceramics and building materials.     

Effect of hydration on conductivity of Ba4La x Ca2 − x Nb2O11 + 0.5x (x = 0.5, 1, 1.5, 2) phases

Substitution of Ca by La in initial cubic double perovskite Ba₄(Ca₂Nb₂)O₁₁[VO]₁ allowed obtaining phases with a similar structure with a lower content of structural oxygen vacancies, Ba₄(La _x Ca_{2 ? x} Nb₂)O_{11 + 0.5x} [VO]_{1 ? 0.5x} (x = 0.5, 1, 1.5, 2). The impedance technique was used to measure the temperature dependences of conductivity in the atmosphere of dry and humid air. Transport numbers determined using the EMF method in an oxygen-air and water steam concentration cells point to the predominantly hole nature of conductivity in the high-temperature region (T > 600°C) and to predominance of proton conductivity in the low-temperature region. Activation energies of hole and proton conductivity were calculated. Thermogravimetric measurements were carried out under heating from 25 to 1000°C with simultaneous mass-spectrometric determination of evolved H₂O and CO₂. The properties of the studied Ba₄(La _x Ca_{2 ? x} Nb₂)O_{11 + 0.5x} (x = 0.5, 1, 1.5, 2) phases were compared with the earlier studied Ba_{4 ? x} La _x (Ca₂Nb₂)O_{11 + 0.5x} phases with similar lanthanum content.     

Electrochemical sensors based on platinized Ti1 − x Ru x O2

Electrocatalysts based on platinized titania modified with ruthenia (0–9 mol %) were studied. The synthesized materials were investigated as working electrodes in potentiometric sensors sensitive to hydrogen and carbon monoxide. All electrocatalysts showed reproducible behavior at pure gas concentrations from 400 to 4000 ppm. In CO-H₂ mixtures with comparable concentrations of both gases, the sensors were selective toward hydrogen at ≥0.05 mol % Ru, but not selective to hydrogen or CO at less than 0.05 mol % Ru in the substrate.     

Structural and dynamical studies of δ-Bi2O3 oxide-ion conductors: II. A structural comparison of (Bi2O3)1−x(M2O3)x for M = Y,Er, and Yb

We report the results of diffuse elastic neutron scattering studies of the superionic solid solutions (Bi₂O₃)_1−x(Er₂O₃)_x and (Bi₂O₃)_1−x(Yb₂O₃)_x, and also the result of a Bragg diffraction study of (Bi₂O₃)_0.75(Er₂O₃)_0.25. All the data suggest that Er³⁺-doped δ-Bi₂O₃ is structurally very similar to the fluorite-related solid solution (Bi₂O₃)_1−x(Y₂O₃)_x studied previously, both in terms of the average structure as determined by Bragg scattering and in terms of local ordering on the anion sublattice as detected by diffuse scattering. The ordered regions are described as microdomains of a rhombohedral phase. The Yb³⁺-doped materials also show short-range anion ordering, but over shorter distances than in the other two cases. There is evidence of cation ordering between Bi³⁺ and Yb³⁺ near the low-dopant boundary of the fluorite phase. The possible use of quasi elastic neutron scattering to monitor oxide-ion transport in the system (Bi₂O₃)_1−x(Er₂O₃)_x is discussed.     

Structural and dynamical studies of δ-Bi2O3 oxide ion conductors: IV. An EXAFS investigation of (Bi2O3)1−x(M2O3)x for M = Y,Er, and Yb

The local structural environments of Bi³⁺ and dopant cations in the fluorite-structured solid solutions (M₂O₃)_x(Bi₂O₃)_1−x (M = Y, Er, Yb) have been studied using extended X-ray absorption fine structure techniques. The results show that the BiO shell is heavily disordered with an asymmetric radial distribution function. The Bi³⁺ ion tends to be displaced from its centrosymmetric, cube center site. The first coordination shell of the dopant is comparatively ordered. Varying the dopant cation has a small effect on the local structural environment and increasing the dopant concentration causes a small increase in the degree of local order. Data obtained over a range of temperatures show that the large anisotropy in the BiO shell is attributable to static displacements from the perfect lattice sites. The degree of correlation between the thermal vibrations of the anion sublattice and those of the Bi atoms differs from that observed between those of the anion sublattice and the dopant atoms; the significance of this for ionic conductivity is discussed.     

二维M_2XO_(2-2x)(OH)_(2x)(M=Ti,V;X=C,N)析氢催化活性的第一性原理研究

MXene是一种新型的二维析氢催化材料,其表面容易被亲水基团O和OH混合覆盖。我们基于第一性原理计算的方法,研究了M_2XO_(2-2x)(OH)_(2x)(M=Ti,V;X=C,N)的析氢催化活性。计算结果显示,M_2XO_(2-2x)(OH)_(2x)的析氢催化活性与其表面OH覆盖率(X)密切相关。对Ti_2CO_(2-2x)(OH)_(2x)来说,OH覆盖率不超过1/3时,具有优异的析氢催化活性。对Ti_2NO_(2-2x)(OH)_(2x)、V_2CO_(2-2x)(OH)_(2x)和V_2NO_(2-2x)(OH)_(2x)来说,OH覆盖率分别达到4/9、1/3和5/9时,才具有最佳的析氢催化活性。接着,电荷分析显示OH覆盖率会显著影响M_2XO_(2-2x)(OH)_(2x)活性位点O基团的电荷量。最后,我们从态密度的角度揭示了析氢催化活性变化的原因,即活性位点O基团的氧化性随OH覆盖率的增大而被削弱。因此,本文提出了调节表面OH覆盖率来获取M_2XO_(2-2x)(OH)_(2x)最佳析氢催化活性状态的方法,这在工业制氢生产过程中具有重要的应用价值。     

Electrochemical reduction of NO and O2 on La2−x Sr x CuO4-based electrodes

A series of La_2 − x Sr _x CuO₄ (x = 0.0, 0.05, 0.15, 0.25 and 0.35) compounds was investigated for the use of direct electrochemical reduction of NO in an all-solid-state electrochemical cell. The materials were investigated using cyclic voltammetry in 1% NO in Ar and 10% O₂ in Ar. The most selective electrode material was La₂CuO₄, which had an activity of NO reduction that was 6.8 times higher than that of O₂ at 400 °C. With increasing temperature, activity increased while selectivity decreased. Additionally, conductivity measurements were carried out, and the materials show metallic conductivity behavior which follows an adiabatic small polaron hopping mechanism.     

Electrical properties of Ba2(In1 − x Al x )2O5 solid solutions

The electric conductivity of perovskite-like Ba₂(In_{1 ? x} Al _x )₂O₅ solid solutions (0 < x ≤ 0.20) characterized by structural disordering in the oxygen sublattice was studied as a function of temperature and partial pressure of oxygen in an atmosphere with a low content of water vapors ( $p_{H_2 O}$ = 3 × 10^?5 atm). When In³⁺ was partially replaced by Al³⁺, the oxygen ion conductivity increased because of the disordering of oxygen structural vacancies, leading to a significant increase in the total electric conductivity of the samples.     

Electric properties of oxyfluorides Ba2In2O5−0.5x F x with brownmillerite structure

Synthesis of fluoro-substituted substances based on brownmillerite Ba₂In₂O₅ is carried out. The width of the homogeneity region of the Ba₂In₂O_5?0.5x F _x (0 < x ≤ 0.25) solid solution was established using X-ray analysis. Measurement of temperature dependences of conductivity in atmospheres with different partial pressure of water vapor (pH₂O = 3.3 and 2 × 10³ Pa) showed an increase in conductivity at T ≤ 550°C in a humid atmosphere, which is due to appearance of proton transport. The dependence of conductivity on partial oxygen pressure (pO₂ = 0.21 × 10⁵ to 10^?15 Pa) is studied in the temperature range of 500–1000°C; ion transport numbers are calculated. The method of polarization measurements was used to determine transport numbers of fluoride. Total conductivity is divided into ion (proton, oxygen, and fluoride ion) and electron components. Analysis of concentration dependences of conductivities showed that low concentrations of fluoride allow increasing both the total and partial conductivities (oxygen-ion and proton) and, besides, allow shifting the “order-disorder” phase transition by 100°C to the low temperature range.