The solid solutions based on lanthanum manganite as the cathod materials for bismuth-containing solid electrolytes

Substituted lanthanum manganites with the general composition La_1–x Bi _x Mn_1–y Fe(Ni,Cu)yO_{3 + δ} and unit cells in rhombohedral (space group (sp. gr.) R-3c) and/or orthorhombic (sp. gr. Pnma) symmetry are synthesized and attested. They are characterized by permanent excessive oxygen nonstoichiometry within a single structure type at room temperature, independent of the dopant concentration. These materials are adequately mechanically compatible with bismuth niobates. The interval of their chemical compatibility with bismuth-containing compounds is limited by 700–800°C. In this region, the conductivity of composites of substituted lanthanum manganites and bismuth-containing electrolytes is higher as compared with individual compounds. The use of individual manganites or their composites as the electrodes in cells with bismuthcontaining electrolytes increases the total conductivity of the cells.     

X-ray spectroscopy of lanthanum manganites: Nature of doping holes,correlation effects,and orbital ordering

The Mn3s X-ray photoelectron spectra of manganites were studied. It was shown that for the formal valence of manganese from 3+ to 3.3+, the doping holes are O2p in character; as the valence of manganese increases further, the Mn3d states acquire holes. For La_0.7Sr_0.3MnO₃, the Mn3p-3d resonance spectra provided information about the occupied and unoccupied Mn3d states, and the correlation energy U = 6.7 eV was determined experimentally. An analysis of X-ray dichroism on the L absorption spectra of three-dimensional La_7/8Sr_1/8MnO₃ showed that the cooperative Jahn Teller distortion of the orthorhombic phase at 240 K was related to (x ² ? z ²)/(y ² ? z ²) type orbital ordering.     

Alkali (alkaline-earth) metal,aluminum, and titanium complex orthophosphates: Synthesis and characterization

Phase formation in the A_{1 + x} Al _x Ti_{2 ? x} P₃O₁₂ (A = Li, Na, K, Rb, or Cs; 0 ≤ x ≤ 2.0) and B_{0.5(l + x)}Al _x Ti_{2 ? x} P₃O₁₂ (B = Mg, Ca, Sr, or Ba; 0 ≤ x ≤ 2.0) systems was studied using X-ray powder diffraction, electron probe microanalysis, and IR spectroscopy. The following double and triple orthophosphates were found to exist: A_{1 + x} Al _x Ti_{2 ? x} (PO₄)₃ with A = Li (0 ≤ x ≤ 0.3), Na (0 ≤ x ≤ 1.0), K (x = 0, 1.0, or 2.0), Rb (x = 0, 1.0, or 2.0), or Cs (0 ≤ x ≤ 1.0) and B_{0.5(l + x)}Al _x Ti_{2 ? x} (PO₄)₃ with B = Mg and Ba (x = 0), Ca and Sr (0 ≤ x ≤ 0.2). These orthophosphates crystallize in the structure types of kosnarite, langbeinite, cesium titanium arsenate, potassium aluminum phosphate, or rubidium aluminum phosphate. Their crystal parameters were calculated. For CsTi₂(PO₄)₃ (x = 0), Rietveld refinement was carried out: space group Ia \(\bar 3\) d, Z = 32, a = 19.909(5) Å, V = 7892(1) ų. This compound has a framework structure. The framework is built of TiO₆ octahedra and PO₄ tetrahedra; eight- and 12-coordinated Cs⁺ cations populate interstices.     

Systems Li<Subscript>2</Subscript>O(Na<Subscript>2</Subscript>O)-CdO-V<Subscript>2</Subscript>O<Subscript>5</Subscript>: Phase composition and phase diagrams

The subsolidus phase composition of the M₂O-CdO-V₂O₅ systems with M = Li or Na is studied. Double orthovanadates MCdVO₄ and MCd₄(VO₄)₃ form solid solutions of composition Li_{1 ? 2x/3}Cd _x/3CdVO₄ (0 ≤ x ≤ 1, orthorhombic space group Cmcm, modulation at x = 0.6) and Na_{3 ? 2x} Cd_{3 + x} (VO₄)₃ (0 ≤ x ≤ 0.10 and 0.30 ≤ x ≤ 1, orthorhombic space group Cmcm and Pn2₁ a or Pnma, respectively). In the range 0.10 < x < 0.30, the end-members of the solid solutions coexist. Isothermal sections of the systems are mapped.     

Formation of Nd<Subscript>1–<Emphasis Type="Italic">x</Emphasis></Subscript>Bi<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>FeO<Subscript>3</Subscript> Nanocrystals under Conditions of Glycine-Nitrate Synthesis

Nd_1–xBi_xFeO₃ nanocrystals with crystallite size 30?60 nm have been prepared under conditions of glycine–nitrate burning. Single-phase Nd_1–xBi_xFeO₃ nanocrystals are formed over the entire studied concentrations range if the glycine–nitrate synthesis is performed in excess of the oxidizer. Under these conditions, a continuous range of the Nd_1–xBi_xFeO₃ solid solutions (0 ≤ х ≤ 0.75) crystallized in the rhombic system (space group Pbnm) are formed without crystallization of the burning intermediates. The Nd_1–xBi_xFeO₃ solid solutions (х = 0.775, 0.8) crystallize in the rhombic system (space group Pbаm).     

Synthesis,structure, and conduction of solid solutions BIMEVOX (Me = Cu,Ti)

Conditions for synthesizing single-phase solid solutions Bi₄V_{2 ? x} Cu _x/2Ti _x/2O_{11 ? x} and Bi_{4 ? x/2}V_{2 ? x/2}Cu _x/2Ti _x/2O_{11 ? x/2} are studied. The sequence of phase transformations is determined. Possible domains of stability of polymorphic modifications and the overall conductivity as a function of temperature and composition are studied. The structure of the γ-modification is refined using Rietveld’s full-profile analysis.     

Crystal structure and conduction of BICUTIVOX

Existence boundaries, structure, and transport parameters were studied for Bi₄V_{2 ? x} Cu _x/2Ti _x/2O_{11 ? x} solid solutions. Doping levels within x = 0.025–0.15 distort the C2/m crystal lattice (this lattice is characteristic of individual the Bi₄V₂O₁₁ phase) and lowers its symmetry to triclinic. The solid solutions with 0.25 ≤ x ≤ 0.30 crystallize in tetragonal space group I4/mmm. High-temperature X-ray diffraction and dilatometry measurements for Bi₄V_{2 ? x} Cu _x/2Ti _x/2O_{11 ? x} (x ≤ 0.35) solid solutions verified the existence of three structural varieties within 298–1023 K. Electrical conductivity of BICUTIVOX was studied by impedance spectroscopy as a function of temperature, composition, and oxygen partial pressure. Equivalent circuits of cells were analyzed. Features of electrical conductivity versus temperature for the structural varieties are noted. Above 873 K, the solid solutions samples with x = 0.05 have the highest conductivity. At lower temperatures, higher conductivities are in the solid solutions that retain the γ phase in the low-temperature region. The dominant oxygen-ion conduction mechanism was discovered in the solid solutions.     

Heat capacity and thermodynamic functions of new cobalt manganites NdM<Subscript>2</Subscript><Superscript>I</Superscript> CoMnO<Subscript>5</Subscript> (M<Superscript>I</Superscript> = Li,Na, and K) in the range of 298.15–673 K

Temperature dependences of the heat capacity of cobalt manganites NdM₂ ^I CoMnO₅ (M^I = Li, Na, and K) are studied by means of dynamic calorimetry in the range of 298.15?673 K. It is found that λ-shaped effects are observed on the C _p ^° ~ f (T) curve of cobalt manganites, due probably to second order phase transitions. Based on the experimental data, equations for the temperature dependences of the heat capacity of cobalt manganite are derived with allowance for the temperatures of phase transitions. The values of thermodynamic functions Н°(T)–Н°(298.15), S°(T), and Ф^хх(T) are calculated.     

Effect of Active Fillers on Properties of Heat-Resistant Composites

The effect of active fillers such as titanium nitrides TiN _x , carbides TiC _x , and carbonitrides TiC _x N _y (0.5 < x or x + y ≤ 1.0) on properties of polymeric composites based on thermostable binders PAIS-104, SFP-012 AK-30, and ED-20 is studied.     

XPS spectra of vanadium-doped disulfides CuCrS<Subscript>2</Subscript>

The charged state of atoms in layered cation-substituted disulfides CuCr_1?x V _x S₂ (x = 0?0.4) was studied using X-ray photoelectron spectroscopy. The study was performed with polycrystalline powder and ceramic samples of chromium-copper disulfides. CuCr_1?x V _x S₂ samples were shown to comprise differently charged atoms of chromium, copper and vanadium, the charged state of which varies with the concentration of vanadium cations (x).     

Extraction-pyrolytic synthesis and luminescent properties of europium and terbium polytantalates

The promise of synthesis of europium and terbium polytantalates MTa _x O _y , where М = Eu, Tb; x = 7, y = 19; x = 5, y = 14; x = 3, y = 9 by low-temperature extraction-pyrolytic method has been shown. Luminescent properties of the prepared polytantalates have been assessed from excitation and luminescence spectra at 300 K. The dependence of luminescent characteristics of the studied rare earth metal polytantalates on the temperature and time of precursor pyrolysis has been established.     

Phase equilibria involving solid solutions in the Li–Mn–O system

Phase equilibria involving LiMn₂O_4-, Li₂MnO_3-, LiMnO_2-, Mn₃O_4-, and MnO-base solid solutions were studied with varied temperature and partial oxygen pressure. The \({P_{{o_2}}}\)–T and x–y projections of the P–T–x–y phase diagram of the Li–Mn?O system were constructed, as well as the key x–y isotherms of the Li₂O–MnO–MnO₂ quasi-ternary system. In some experiments, the authors’ hydride lithiation method was employed to prepare lithium-rich homogeneous three-component nonstoichiometric phases.     

Synthesis and study of solid solutions between cobalt and nickel phosphates with varied degree of anion protonation

Continuous substitutional solid solutions between cobalt and nickel phosphates with varied degree of anion protonation were obtained: Co_1?x Ni _x HPO₄·1.5H₂O and (Co_1?x Ni _x )₃(PO₄)₂·8H₂O, where 0 ≤ x ≤ 1.00. The thermolysis of the solid solutions was studied by the example of Co_1?x Ni _x HPO₄·1.5H₂O. The phases synthesized were compared with the previously described continuous solid solution Co_1?x Ni _x (H₂PO₄)₂·2H₂O.     

A study of phase formation in the subsolidus region of the system Na<Subscript>2</Subscript>MoO<Subscript>4</Subscript>-MnMoO<Subscript>4</Subscript>-Cr<Subscript>2</Subscript>(MoO<Subscript>4</Subscript>)<Subscript>3</Subscript>

Phase relationships in the subsolidus region of the system Na₂MoO₄-MnMoO₄-Cr₂(MoO₄)₃ were studied by means of X-ray diffraction and differential-thermal analyses. The possibility of obtaining a variablecomposition phase Na_1?x Mn_1?x Cr_1+x (MoO₄)₃ (0 ≤ x ≤ 0.5) and ternary molybdate NaMn₃Cr(MoO₄)₅ was examined. The temperature dependence of the conductivity of the phase Na_1?x Mn_1?x Cr_1+x (MoO₄)₃ was analyzed.     

Structure and properties of solid solutions based on bismuth niobate Bi<Subscript>3</Subscript>NbO<Subscript>7</Subscript>

Solid solutions Bi₃Nb_1–yW_yO_{7 ± δ}, Bi₃Nb_1–yV_yO_{7 ± δ}, Bi₃Nb_1–yFe_yO_{7 ± δ} (y = 0.1–0.5; Δy = 0.1), and Bi_3–xY_xNb_1–yW_yO_{7 ± δ} (x = 0.05, 0.1; y = 0–0.3; Δy = 0.1) have been studied. The homogeneity ranges of the solid solutions and crystal-chemical parameters have been determined by means of X-ray powder diffraction. The electrical conductivity of sintered samples has been studied by impedance spectroscopy. The joint introduction of yttrium and tungsten into the niobium sublattice does not lead to an increase in the conductivity of solid solutions, and the change of the dopant type has no noticeable effect on this conductivity.     

Chemical etching of Cd<Subscript>1 − <Emphasis Type="Italic">x</Emphasis></Subscript>Mn<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>Te solid solution single crystals with iodine solutions in methanol

Chemical etching of Cd_{1 ? x} Mn _x Te (0.04 < x < 0.5) solid solution (ss) single crystals in I₂ + CH₃OH etching mixtures was studied. Concentration and kinetic curves of etching rates were plotted. As the manganese concentration of the solid solution increases, the rates of their etching by iodine-methanol etchants increase, too. The etchant compositions and chemical-dynamic polishing protocols for Cd_{1 ? x} Mn _x Te single crystals were optimized.     

Preparation,structure, and charge transport characteristics of BIFEVOX ultrafine powders

Existence boundaries, structure, and transport parameters of ultrafine powders were studied in Bi₄V_{2 ? x} Fe _x O_{11 ? x} (BIFEVOX) solid solutions. The details of synthesis of the solid solutions via liquid precursors are analyzed comparatively. In general, BIFEVOX formation via liquid precursors is similar to phase formation in solid-phase synthesis. With low iron levels (x = 0.05–0.1), solid solutions are formed in the monoclinic α phase (space group C2/m) The compositions with x = 0.125 and 0.15 are mixtures of α- and β phases. In the range 0.2 < x < 0.7, the Bi₄V_{2 ? x} Fe _x O_{11 ? x} solid solution has the structure of the γ phase of Bi₄V₂O₁₁ (space group I4/mmm). The β phase in the system in question has a very narrow existence range in the vicinity of x = 0.175. The average particle sizes of the powders prepared by various methods are within 0.5–3 μm. In the powders prepared via liquid precursors, however, the distribution peak shifts toward smaller sizes, to 0.3–1 μm. Mechanical activation conserves the structure of the γ phase of BIFEVOX, and unit cell parameters change only insignificantly; however, the crystal lattice is slightly distorted. The electrical conductivity of BIFEVOX was studied as a function of temperature, preparation technology, and composition using impedance spectroscopy. Equivalent circuits of cells were analyzed. The conductivity of samples prepared by solution technology is always higher than for samples prepared by the solid-phase process. Features of electrical conductivity versus temperature for various phases are noted. All transitions on the conductivity curves match the features of linear thermal expansion curves. Compositions with doping levels x= 0.1–0.3 have the highest total conductivities.     

Effects of base composition and dopants on the properties of hexagonal ferrites

The effects of the base composition and dopants on the saturation magnetization and coercivity of hexaferrites BaAl_xFe_12–xO₁₉, SrAl_xFe_12–xO₁₉, BaGa_xFe_12–xO₁₉, SrGa_xFe_12–xO₁₉, BaSc_xFe_12–xO₁₉ and SrSc_xFe_12–xO₁₉ have been studied. Isomorphic substitutions of Al₂O₃, Ga₂O₃, and Sc₂O₃ for Fe₂O₃ in barium and strontium ferrites are found to increase coercivity due to increasing crystallographic anisotropy constant and to reduce the saturation magnetization value. Processes controlling microstructure formation, specifically recrystallization processes, are shown to have a noticeable effect on the level of properties of the ferrites under study with the use of dopants. The most efficient dopants are boron, calcium, and silicon oxides, which provide the formation of relatively fine-grained structures. The increased coercivity upon doping with these dopants is also due to the formation of grain-boundary interlayers of a nonmagnetic glassy phase and the associated efficient retardation of moving domain walls.     

Phase formation in the Ag<Subscript>2</Subscript>MoO<Subscript>4</Subscript>-MgMoO<Subscript>4</Subscript>-Al<Subscript>2</Subscript>(MoO<Subscript>4</Subscript>)<Subscript>3</Subscript> system

The subsolidus region of the Ag₂MoO₄-MgMoO₄-Al₂(MoO₄)₃ ternary salt system has been studied by X-ray phase analysis. The formation of new compounds Ag_{1 ? x} Mg_{1 ? x} Al_{1 + x} (MoO₄)₃ (0 ≤ x ≤ 0.4) and AgMg₃Al(MoO₄)₅ has been determined. The Ag_{1 ? x} Mg_{1 ? x} Al_{1 + x} (MoO₄)₃ variable-composition phase is related to the NASICON type structure (space group R \(\bar 3\) c). AgMg₃Al(MoO₄)₅ is isostructural to sodium magnesium indium molybdate of the same formula unit and crystallizes in triclinic system (space group P \(\bar 1\), Z = 2) with the following unit cell parameters: a = 9.295(7) Å, b = 17.619(2) Å, c = 6.8570(7) Å, α = 87.420(9)°, β = 101.109(9)°, γ = 91.847(9)°. The compounds Ag_{1 ? x} Mg_{1 ? x} Al_{1 + x} (MoO₄)₃ and AgMg₃Al(MoO₄)₅ are thermally stable up to 790 and 820°C, respectively.     

Isomorphic substitution of neodymium and gadolinium for calcium in synthetic hydroxovanadate

Isomorphic substitution of neodymium and gadolinium for calcium in synthetic hydroxovanadate Ca_{5 ? x} M _x (VO₄)₃(OH)_{1 ? x} O _x (M = Nd, Gd) is studied in the range 700–1000°C using X-ray powder diffraction, single-crystal X-ray diffraction (Rietveld technique), and IR spectroscopy. Single-phase solid solutions at 800°C are formed with x ≤ 0.35 for M(III) = Nd and x ≤ 0.3 for M(III) = Gd. With high x, the apatite solid solution coexists with Ca₃(VO₄)₂, Nd₂O₃, and X phases. With increasing x in the homogeneous region, the intensity of the bands of stretching vibrations and librations of OH groups decrease. Single-crystal X-ray diffraction shows that neodymium and gadolinium substitute for calcium in solid solutions mostly in Ca(2) positions.