S. F. Bychkov

Study of high-temperature oxygen permeability in Sr1 − xLaxCo0.8 − yNbyFe0.2O3 − z perovskites

The oxygen permeability of ceramic SrCo0.8 − yFe0.2NbyO3 − z (0 ≤ y ≤ 0.2) and La0.3Sr0.7Co0.6Fe0.2Nb0.2O3 − z disc membranes as a function of temperature and oxygen partial pressure was studied. Kinetic analysis was performed based on the experimental data on oxygen permeability as a function of oxygen partial pressure.

Oxygen release from SrCo0.8Fe0.2O3 − δ

We have studied oxygen release from a membrane material with the composition SrCo0.8Fe0.2O3 − δ of various sizes in the temperature range 600–900°C in a flow reactor at oxygen partial pressures from 0.2 to 10−5 atm. The results demonstrate that the oxygen release from samples 50 μm to 2 mm in size at temperatures above 800°C can be described in terms of a quasi-equilibrium model. For fine powders, ≤63 μm in size, the temperature range of quasi-equilibrium oxygen release begins at t ≥ 600°C.

Oxygen permeability of hollow fiber membranes of composition Ba0.5Sr0.5Co0.78W0.02Fe0.2O3–δ

Hollow fiber membranes of composition Ba0.5Sr0.5Co0.78W0.02Fe0.2O3–δ (BSCFW2) have been synthesized by the phase inversion method. The structure of hollow fiber membranes has been studied by scanning electron microscopy, and the phase composition of the material before and after the tests has been determined.

Relation between oxygen stoichiometry and thermodynamic properties and the electronic structure of nonstoichiometric perovskite La0.6Sr0.4CoO3−δ

Continuous phase diagram 3 - δ - logu2009pO2 - T of the nonstoichiometric perovskite La0.6Sr0.4CoO3-δ was obtained in a gas flow reactor by means of the quasi-equilibrium oxygen release technique. The thermodynamic properties of oxides were determined as a function of oxygen nonstoichiometry. Within the framework of the itinerant electron model, the dependence of the oxide nonstoichiometry on the oxygen activity was related to the density of electronic states near the Fermi level.

Modification of mixed conducting Ba0.5Sr0.5Co0.8Fe0.2O3–δ by partial substitution of cobalt with tungsten

The Ba0.5Sr0.5Co0.8–xWxFe0.2O3–δ (х = 0–0.1) materials prepaMIECred by partial substitution of cobalt in BSCF with tungsten were studied. The tungsten solubility limit in the structure of cubic perovskite BSCF was shown to be ~2%. The doping with the highly charged W6+ (2%) cation improved the functional properties of BSCF: it increased the oxygen permeability and membrane stability in the CO2-containing atmosphere and suppressed the cubic–hexagonal perovskite polymorphic transition. This stabilizes high oxygen fluxes during long-term stability tests.

High-temperature oxygen nonstoichiometry determination in mixed ionic-electronic conducting oxides

We have developed a new method for determining oxygen nonstoichiometry (3 − δ) as a continuous function of oxygen partial pressure

Study of the oxygen exchange kinetics in the nonstoichiometric oxide SrFeO3–δ under isostoichiometric conditions using the oxygen partial pressure relaxation technique

left( {p_{O_2 } } right)

Improvement of Ba0.5Sr0.5Co0.8Fe0.2O3−δ functional properties by partial substitution of cobalt with tungsten

at high temperatures in mixed ionic-electronic conducting oxides. A proposed mathematical model allowed us to assess the contribution of the oxygen released from a sample to the oxygen partial pressure at the outlet of a flow reactor after a steplike change of oxygen partial pressure in the incoming gas from 0.2 to 10−5 atm and to calculate 3 − δ as a function of