The effect of the halide-ion (F<Superscript>–</Superscript>, Cl<Superscript>–</Superscript>) dopant nature on the local structure and hydration processes of brownmillerite Ba<Subscript>2</Subscript>In<Subscript>2</Subscript>O<Subscript>5</Subscript>

Halogen-substituted barium indate Ba₂In₂O₅ based brownmillerites Ba_1.95In₂O_4.9F_0.1 and Ba_1.95In₂O_4.9Cl_0.1 have been synthesized. It has been verified radiographically that the single-phase condition is satisfied. The effect of the substituent ion nature on parameters of the crystalline lattice and lengths of In–O bonds has been revealed. The propensity of the phases under study for hydration and formation of energetically unequal ОН^– groups in the structure has been proved. In both the cases of doping, the degree of hydration decreased as compared to barium indate Ba₂In₂O₅, which is caused by the participation of the halide ion in the tetrahedral site of indium.     

Lithium conducting solid polymer electrolytes based on polyacrylonitrile copolymers: Ion solvation and transport properties

The systems poly(butadiene-co-acrylonitrile) (PBAN) - lithium salts have been studied by means of X-ray and IR spectroscopy, optical microscopy and ac- and dc-conductivity measurements. X-ray and microscopy studies have confirmed that PBAN dissolves LiClO₄ up to [CN]/[Li] ≈ 2: 1. IR spectra of the samples with LiAsF₆, LiCF₃SO₃ and LiClO₄ have indicated the coordination between Li⁺ and the polar CN groups of PBAN. So, PBAN was found to be a suitable polymer matrix for SPE. The polymer films exhibited predominant ionic conductivity. Measurements of conductivity and Li transport numbers versus temperature over a wide range of salt concentrations revealed the existence of two concentration regions (within the limits of salt solubility) corresponding to liquid-like and glass-like ion transport mechanisms. New solid polymer electrolyte with lithium single-ion conductivity of 10⁻³ S cm⁻¹ at 25 – 95 °C was obtained. Paper presented at the 4th Euroconference on Solid State Ionics, Renvyle, Galway, Ireland, Sept. 13–19, 1997     

Strontium Tantalates with a Perovskite Structure: Their Conductivity and High-Temperature Interaction with Water

The interaction of perovskite-like solid solutions Sr_{6 – 2x} Ta_{2 + 2x} O_{11 + 3x} (x= 0–0.28) with water is studied, along with dependences of the solutions' conductivity on their composition and the atmosphere's temperature and humidity. The Sr_{6 – 2x} Ta_{2 + 2x} O_{11 + 3x} phases with high concentrations of structural oxygen vacancies are high-temperature mixed oxygen–hydrogen ionic conductors whose conduction is sensitive to the presence of water vapor up to 900°C. According to a thermogravimetric study, the amount of water incorporated into the complex-oxide matrix is proportional to the concentration of structural oxygen vacancies. The process of water incorporation is considered in terms of crystalline and chemical properties of the structure. The oxygen-deficient perovskites containing coordination-unsaturated metalatoms can reconstruct their coordination polyhedron by adding water molecules, with subsequent partial dissociation of water to hydroxyl groups. The proposed mechanism explains different states of water in the oxide and a two-stage nature of its removal: water molecules coordinating the metal atom and those surrounding OH^–leave the core in the first and second stages, respectively.     

Electric properties of solid solutions based on strontium tantalate with perovskite-type structure. Oxygen-ionic conductivity

Total conductivity of Sr_{6 − 2x} Ta_{2 + 2x} O_{11 + 3x} (0 ≤ x ≤ 0.33) solid solutions with a cryolite structure is studied in the atmosphere with a low water vapor content under variation of the temperature (500 < T < 1000°C) and oxygen activity in the gas phase (10⁻¹⁸ < aO₂ < 0.21). Conductivity is divided into components. It is found that both the oxygen-ionic conductivity and the mobility of oxygen ions increase and the percentage of p-type electronic conductivity decreases at an increase in the concentration of oxygen vacancies. It is shown that compositions with a high strontium oxide content (0 ≤ x < 0.15) and accordingly high concentration of oxygen vacancies correspond to the maximum values of the oxygen-ionic conductivity and low activation energies. The Sr₆Ta₂O₁₁ and Sr_5.92Ta_2.08O_11.12 compositions in a wide range of aO₂ are characterized by negligibly low fractions of electronic conductivity component. For the compositions of x > 0.15, a transition occurs from the electrolytic region to mixed oxygen-hole conductivity character (at aO₂ = 0.21) at an increase in the oxygen activity.     

Structure and electrical properties of oxygen-deficient strontium copper niobate

The transport properties of Sr_5.66 Cu_0.14Nb_2.20 O_11.30 double perovskite, which enters the homogeneity region of (Sr_1-y Cu _y )₆–_2x Nb_2+2x O_11+3x solid solution, are concerned. The total conductivity is differentiated into terms over wide ranges of temperatures and oxygen partial pressures $ p_{O_2 } $ p_{O_2 } in dry and humid atmospheres. When $ p_{O_2 } $ p_{O_2 } is low or high, a test sample has dominant electron transport of n- or p-type, respectively. In air ($ p_{O_2 } $ p_{O_2 } = 0.21 atm), the p-type electron conductivity term increases with temperature elevation. In a humid atmosphere ($ p_{H_2 O} $ p_{H_2 O} = 0.02 atm), a sample is capable of a reversible incorporation of water occlusion from the gas phase; as a result, some proton conductivity term appears and ion transference numbers increase over a wide range of $ p_{O_2 } $ p_{O_2 } values.     

Proton transport in perovskites Ba<Subscript>2</Subscript>InMO<Subscript>6</Subscript> (M = Nb,Ta)

The reasons for the appearance of proton conductivity in the complex oxide Ba₂InMO₆ phases (M = Nb, Ta) with a formally complete oxygen sublattice were determined. The formation of oxygen vacancies in the structure as a result of the violation of stoichiometry causes the introduction of water, the amount of which does not exceed 0.02 mol per formula unit of the composition. The appearance of proton defects even in low concentrations provides the dominant proton transfer below 500°C.     

Features of the local structure of hydrated fluorine-substituted solid solutions based on Ba2In2O5

It is found for hydrated solid solutions of Ba_2?0.5x In₂O_5?x F _x · nH₂O, Ba₂In₂O_5?0.5y F _y · nH₂O (0 ≤ x ≤ 0.30; 0 ≤ y ≤ 0.24) that increasing the concentration of fluorine lowers the degree of hydration. The composition of proton-containing groups and the places of their localization in the structure of hydrated oxyfluorides are determined. The presence of fluorine in the complex oxide’s structure helps increase the mobility of protons.     

Hydration and the State of Oxygen–Hydrogen Groups in the Complex Oxide BaLaIn0.9Nb0.1O4.1 with the Ruddlesden–Popper Structure

Russian Journal of Physical Chemistry A - Compounds BaLaInO4 and BaLaIn0.9Nb0.1O4.1 with the Ruddlesden–Popper structure, are synthesized. The ability of these phases with respect to...     

The Local Structure and Hydration Processes of Halogen-Substituted Perovskites Based on Ba4In2Zr2O11

Optics and Spectroscopy - Halogen-substituted perovskites Ba4In2Zr2O10.95F0.1 and Ba4In2Zr2O10.95Cl0.1 are synthesized, and their single-phase composition is verified by X-ray diffraction analysis....     

Effect of phosphate doping on electric properties and chemical stability of Ba<Subscript>4</Subscript>Ca<Subscript>2</Subscript>Nb<Subscript>2</Subscript>O<Subscript>11</Subscript> protonic conductor

Conductivity of perovskite phosphate–substituted solid solutions of Ba₄Ca₂Nb_{2 –x} P _x O₁₁ (0.0 ≤ x ≤ 0.5) was studied as a function of temperature, partial pressure of oxygen and water vapors. It is proved that the studied systems are protonic conductors at the temperatures below 600°C in the atmosphere with elevated content of water vapors (pH₂O = 1.92 × 10^–2 atm). Introduction of the tetrahedral [PO₄] group in the complex oxide matrix of Ba₄Ca₂Nb₂O₁₁ results in an increase in the oxygen–ionic (dry air, pH₂O = 1.91 × 10^–4 atm) and protonic conductivities (wet air, pH₂O = 1.92 × 10^–2 atm). Is it found that the doping causes a considerable increase in chemical stability of phases with respect to carbon dioxide.