Kinetic effects in n -CdAs2, p -ZnAs2, and Cd x Zn1 ? x As2 solid solutions

The electrical resistivity and Hall factor in n-CdAs₂, p-ZnAs₂, and n-Cd _x Zn_{1 − x} As₂ were measured at hydrostatic pressures up to 9 GPa and quasi-hydrostatic pressures up to 50 GPa at room temperature. For n-CdAs₂, a phase transition was discovered at p = 5.5 GPa; for p-ZnAs₂, two phase transitions were discovered: one at P = 10–15 GPa and the other at p = 35–40 GPa. No anomalies were found on ρ(p) and R(p) curves for Cd _x Zn_{1 − x} As₂ when p ≤ 9 GPa. Original Russian Text ? A.Yu. Mollaev, I.K. Kamilov, R.K. Arslanov, L.A. Saipulaeva, R.G. Dzhamamedov, S.F. Marenkin, A.N. Babushkin, 2009, published in Zhurnal Neorganicheskoi Khimii, 2009, Vol. 54, No. 1, pp. 122–125.     

Synthesis and thermolysis of substitutional solid solutions (Cu1?yMy)2(OH)PO4·xH2O (x = 0.1?0.2; M = Zn, Co, Ni)

Substitutional solid solutions (Cu_1−y Zn _y )₂(OH)PO₄·xH₂O (0 ≤ y ⩽ 0.26, x = 0.1−0.2), (Cu_1−y Co _y )₂(OH)PO₄·xH₂O (0 ≤ y ≤ 0.10, x = 0.1−0.2), and (Cu_1−y Ni _y )₂(OH)PO₄·xH₂O (0 ≤ y ≤ 0.08, x = 0.1−0.2) were synthesized. The unit cell parameters of the resulting phosphates were determined, and their IR absorption spectra were measured. The reactants were H3PO4 and mixtures of hydrous carbonates of the appropriate metals. Thermolysis of the solid solutions was examined with (Cu_1−y Co _y )₂(OH)PO₄·xH₂O (0 ≤ y ≤ 0.10, x = 0.1−0.2) as an example.     

Synthesis and study of the properties of K2Y1 ? x ? yEuxTby(MoO4)(PO4) and K2Y1 ? x ? yEuxTby(MoO4)(PO4)1?δ(VO4)δ solid solutions

Al synthesized samples are isostructural and crystallize in the orthorhombic symmetry system, space group Ibca. Particles of the final product of ∼200 nm in size have been obtained. The introduction of the vanadate anion into the matrix composition leads to the lowering of the symmetry of the Eu³⁺ environment and to the rise of the defect luminescence at 450–550 nm because of the unit cell distortion. The luminescence of defects in terbium-europium-containing samples is determined by the sample surface area, which decreases on annealing. The τ, W ₀ and γ parameters of the luminescence kinetics of the samples have been determined.     

The enthalpies of formation of Sm1 + xBa2 ? xCu3Oy substitution solid solutions

The enthalpies of reactions of Sm_{1 + x} Ba_{2 − x} Cu₃O _y substitution solid solutions (x = 0, 0.1, 0.2, 0.3, 0.7, and 0.8) with 1.07 N HCl were measured at 298.15 K in a hermetic isothermic-shell swinging calorimeter. The results and the literature data were used to calculate the standard enthalpies of their formation from simple substances and binary oxides (Δ_f H _298.15^o and Δ_ox H _298.15^o). The dependence of the enthalpy of formation on the degree of samarium substitution for barium was obtained.     

The enthalpies of formation of substitution solid solutions Pr1 + xBa2 ?xCu3Oy

The enthalpies of reactions of substitution solid solutions Pr_{1 + x} Ba_{2 − x}Cu₃O _y , where x = 0, 0.2, 0.4, 0.6, and 0.9, with 1.07 N HCl were measured at 298.15 K in a hermetic swinging isothermic-shell calorimeter. The results and the literature data were used to calculate the standard enthalpies of formation of solid solutions from the elements and oxides. The dependence of the enthalpy of solid solution formation on the degree of praseodymium substitution for barium (x) was revealed.     

Synthesis, crystal and electronic structures, and thermodynamic characteristics of BaCe1 ? xInxO3 ? x/2 solid solutions

New perovskite oxide phases BaCe_{1 − x} In _x O_{3 − x/2} (x = 0.1–0.8) (space group Pbnm) have been synthesized. The unit cell volume of the resulting solid solutions monotonically decreases with an increase in the degree of substitution of indium for cerium due to the contraction of octahedra in perovskite blocks. The thermodynamic stability of the compound BaCe_0.75In_0.25O_2.875 was studied by the solution calorimetry method, and barium cerates were shown to be thermodynamically stable with respect to binary oxides at room temperature. The structure of occupied and vacant states in BaCe_{1 − x} In _x O_{3 − x/2} was determined on the basis of X-ray emission, absorption, and photoelectron spectra, and the energy gap was estimated at ∼2 eV.     

Preparation of a single-phase solid electrolyte La1 ? xSrxGa1 ? yMgyO3 ? (x + y)/2 by self-propagating high-temperature synthesis

Highly dispersed single-phase powders described as La_0.88Sr_0.12Ga_0.82Mg_0.18O_2.85 were prepared using a method based on the principles of self-propagating high-temperature synthesis (SHS). Lanthanum, strontium, gallium, and magnesium nitrates were used in the SHS as “oxidants”, and ethylene glycol was used as the reducing agent. The initial reaction mixture was liquid. According to X-ray diffraction and scanning electron microscopy data, the sample becomes a single phase after annealing of the primary SHS product at 1200°C, which is substantially lower than in other synthetic methods. Using so active powders (grain size of about 100–130 nm), it is possible to reduce the temperature of the final annealing of the ceramics to 1275°C, which gives rise to single-phase finely dispersed ceramics having specific properties.     

Synthesis and study of the variable-composition phase Na1?xCo1?xFe1+x(MoO4)3, 0 ≤ x ≤ 0.4, with nasicon structure

The synthesis conditions for variable-composition phase Na_1−x Co_1−x Fe_1+x (MoO₄)₃, 0 ≤ x ≤ 0.4, crystallizing in the nasicon structure type (R $ \bar 3 $ \bar 3 c) were examined. For this phase, the crystallographic parameters were calculated, vibrational spectra were interpreted, and temperature dependence of electrical conductivity, dielectric constant, and dielectric loss tangent were examined.     

Crystal structures of La1 ? xSr2 + x(GeO4)(V1 ? xMoxO4) (x= 0?0.4) solid solutions

The phase compositions of theLaVO₄-SrMoO₄(1) and Sr₂GeO₄-SrMoO₄ (2) binary systems, which bound the Sr₂GeO₄-LaVO₄-SrMoO₄ (3) ternary system, and the LaSr₂(VO₄)(GeO₄)-Sr₂GeO₄+SrMoO₄ section (4) of system 3 are studied at subsolidus temperatures. Systems 1 and 2 consist of a mixture of the initial compounds, and the La_{1 − x} Sr_{2 + x} (GeO₄)(V_{1 − x} Mo _x O₄) (where 0 ≤ x ≤ 0.4) region of substitutional solid solutions with a palmierite structure is formed in system 3. The unit cell parameters of the solid solutions are determined. The distribution of the lanthanum and strontium cations over two positions of the cationic sublattice is described. Original Russian Text ? V.D. Zhuravlev, V.G. Zubkov, A.P. Tyutyunnik, Yu.A. Velikodnyi, N.D. Koryakin, 2009, published in Zhurnal Neorganicheskoi Khimii, 2009, Vol. 54, No. 1, pp. 135–137.     

Solid solutions of Ba2(In1 ? xAlx)2O5: Structural evolution and hydration processes

Solid solutions of the composition Ba₂(In_{1 − x} Al _x )₂O₅[VO]₁ (0 ≤ x ≤ 0.20) with an incomplete oxygen sublattice were obtained. It was established that, along with an increase in parameter x, there is disordering of oxygen vacant positions and a transition from the structure of brownmillerite to that of defect perovskite. It was demonstrated that the phases under study are characterized by an ability for reversible interaction with water vapors in the temperature range 150–450°C. During this process, proton defects, predominantly in the form of OH⁻ groups, are formed in the oxide structure. We conclude that in a number of solid solutions, the amount of intercalated water declines upon an increase in the aluminum content.     

Ag1 ? xMg1 ? x R1 + x(MoO4)3 Ag+-conducting NASICON-like phases, where R = Al or Sc and 0 ≤ x ≤ 0.5

Ag_{1 − x} Mg_{1 − x} R_{1 + x} (MoO₄)₃ NASICON-like solid solutions, where R = Al or Sc and 0 ≤ x ≤ 0.5, were prepared; their crystal lattice parameters and thermal stabilities were determined. Silver-ion conductivity was measured, and conductivity activation energy values were calculated for various temperature ranges. Above 400°C, Ag_{1 − x} Mg_{1 − x} R_{1 + x} (MoO₄)₃ phases have ionic conductivities comparable to the conductivities of sodium-ion and lithium-ion NASICON-like conductors. The conductivity increases as the tervalent cation radius increases or the amount of mobile silver ions increases.     

New anion-conducting solid solutions Bi1−xTex(O,F)2+δ (x > 0.5) and glass–ceramic material on their base

The anion-excess fluorite-like solid solutions with general composition Bi_1−xTe_x(O,F)_2+δ (x > 0.5) have been synthesized by a solid state reaction of TeO₂, BiF₃ and Bi₂O₃ at 873 K with following quenching. The homogeneity areas and polymorphism of the I ↔ IV Bi_1−xTe_x(O,F)_2+δ phases were investigated. The crystal structure of the low temperature IV-Bi_1−xTe_x(O,F)_2+δ phase has been solved using electron diffraction and X-ray powder diffraction (a = 11.53051(9) Å, S.G. Ia-3, R_I = 0.046, R_P = 0.041). Glass formation area in the Bi₂O₃–BiF₃–TeO₂ (10% TiO₂) system was investigated. IVBi_1−xTe_x(O,F)_2+δ phase starts to crystallize at short-time (0.5–3 h) annealing of oxyfluoride glasses at temperatures above T_g (600–615 K). The ionic conductivity of the crystalline Bi_1−xTe_x(O,F)_2+δ phase and corresponding glass-ceramics was investigated. Activation energy of conductivity E_a = 0.41(2) eV for the IV-Bi_1−xTe_x(O,F)_2+δ crystalline samples and E_a = 0.73 eV for the glass-ceramic samples were obtained. Investigation of the oxyfluoride samples with a constant cation ratio demonstrates essential influence of excess fluorine anions on the ionic conductivity.     

Phase formation in the Ba3? x Sr x Y(BO3)3 system (0 < x < 3)

Phases of a variable composition in the Ba_3−x Sr _x Y(BO₃)₃, system (0 < x < 3) have been investigated for the first time using the solid-phase reactions method. The formation of two series of solid solutions crystallizing in different structural types have been established using X-ray diffraction (D-8 Advance diffractometer, CuK _α radiation, graphite monochromator). Crystal characteristics of obtained phases have been determined. Original Russian Text ? T.N. Khamaganova, 2008, published in Zhurnal Neorganicheskoi Khimii, 2008, Vol. 53, No. 4, pp. 553–556.     

NASICON phases of variable composition K1? x A1? x R1+ x (MoO4)3 (0 ≤ x ≤ 0.2–0.6), where A = Ni, Mg, Co, or Mn and R = Yb, Lu, or Sc

Phases of variable composition K_1−x A_1−x R_1+x (MoO₄)₃) (0 ≤ x ≤ 0.2–0.6), where A = Ni, Mg, Co, or Mn and R = Yb, Lu, or Sc, which crystallize in a NASICON-type structure (space group R c) were synthesized by solid-phase reactions. Their crystal parameters were calculated, and IR and Raman spectra described. Original Russian Text ? N.M. Kozhevnikova, T.N. Khamaganova, 2008, published in Zhurnal Neorganicheskoi Khimii, 2008, Vol. 53, No. 5, pp. 864–865.     

Specifics of pyrohydrolytic and solid-phase syntheses of solid solutions in the (MgGa2O4)x(MgFe2O4)1 ? x system

This work demonstrates the possibility of preparing solid solutions in the (MgGa₂O₄) _x (MgFe₂O₄)_{1 − x} system by pyrohydrolytic and solid-phase methods. It is shown that the products obtained have different specific surface areas depending on the ratio between metal nitrates and citric acid. The composition dependence of the unit cell parameter deviates considerably from the Vegard’s rule. The compounds obtained are found to be stable up to 300°C, which makes them candidate materials for electronics.     

Structure, magnetic, and electric properties of bismuth niobates doped with d -Elements: VI. Magnetic behavior of Bi3Nb3?3 x Ni3 x O15?δ solid solutions

Magnetic susceptibility of nickel-containing solid solutions with layered perovskite-like structure of bismuth niobate, Bi₅Nb₃O₁₅, was studied. High-spin nickel atoms, Ni(III), were present at low concentrations of the solid solutions. The formation of exchange-bonded aggregates (dimers) of nickel(II) atoms with antiferromagnetic type of exchange was found in the solid solutions. The parameters of exchange interactions in the dimer clusters and the distribution of monomers and dimers of nickel atoms were calculated as a function of the solid solution concentration. Original Russian Text ? N.A. Zhuk, I.V. Piir, N.V. Chezhina, 2008, published in Zhurnal Obshchei Khimii, 2008, Vol. 78, No. 3, pp. 393–399. For communication V, see [1].     

Mechanism studies and electrochemical performance optimization on xLiFePO4·(1 ? x)Li3V2(PO4)3 hybrid materials

Hybrid materials xLiFePO₄·(1 − x)Li₃V₂(PO₄)₃ were synthesized by sol–gel method, with phenolic resin as carbon source and chelating agent, methylglycol as surfactant. The crystal structure, morphology and electrochemical performance of the prepared samples were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), cyclic voltammetry (CV), galvanostatic charge–discharge test and particle size analysis. The results show that LiFePO₄ and Li₃V₂(PO₄)₃ co-exist in hybrid materials, but react in single phase. Compared with individual LiFePO₄ and Li₃V₂(PO₄)₃ samples, hybrid materials have smaller particle size and more uniform grain distribution. This structure can facilitate Li ions extraction and insertion, which greatly improves the electrochemical properties. The sample 0.7LiFePO₄·0.3Li₃V₂(PO₄)₃ retains the advantages of LiFePO₄ and Li₃V₂(PO₄)₃, obtaining an initial discharge capacity of 166 mA h/g at 0.1 C rate and 109 mA h/g at 20 C rate, with a capacity retention rate of 73.3% and an excellent cycle stability.     

Structural features of the formation of La1?xCaxFeO3?δ (0 ≤x ≤ 0.7) hetero valent solid solutions

A synthesis method with the use of polymer-salt compositions (calcination temperature 800°C) provides the preparation of various solid solutions of a La_1−x Ca _x FeO_3−δ series in the 0≤ x≤ 0.7 range, which belong to the perovskite structure type. A morphotropic phase transition occurs from the orthorhombic perovskite modification (0≤ x ≤ 0.4) to the cubic one (0.5 ≤ x≤ 0.7). A growing number of microdistortions in the perovskite structure and the formation of a microblock structure in the morphotropic phase transition region are observed with increasing degree of calcium substitution for lanthanum. Calcination of solid solutions with x = 0.6 and 0.7 at temperatures above 1000°C in the air or under conditions of reduced oxygen partial pressure (laboratory vacuum of 10⁻³ Torr) results in the formation of a nanostructured state with coherently grown blocks of perovskite and Grenier phase, which is due to irreversible oxygen loss.     

Phase transitions and ion transport in NASICON materials of composition Li1 + xZr2 ? xInx(PO4)3(x = 0–1)

NASICON materials of composition Li_{1 + x} Zr_{2 − x} In _x (PO₄)₃(x = 0–1) were synthesized. The phase constitution, particle size, and conductivity of these materials were studied as s function of synthesis temperature. High-temperature X-ray powder diffraction was used to study phase transitions in the materials synthesized. Low levels (x ≤ 0.1) partial substitution of indium for zirconium considerably increase the lithium ion conductivity and reduce the activation energy for conduction compared to the parent compound.