Oxygen stoichiometry and isotope exchange of oxides Ba0.5Sr0.5Co0.8Fe0.2O3− doped with Ta, Nb, Mo or W

Consistent interpretation of isotope and chemical oxygen exchange relaxation kinetics in SrFe0.85Mo0.15O3−δ ferrite

“…Oxygen isotope exchange was carried out in a static setup (Fig. 1) equipped with an SRS RGA200 quadrupole mass spectrometer (MS) (8) and consisting of a quartz microreactor (1) (15 cm 3 ) that can be heated up to 700 1C and an exchange zone (2) (660 cm 3 ) connected to gas bottles with natural 32 O 2 and heavy 36 O 2 oxygen. The microreactor could be easily isolated from the rest of the setup using a shut-off valve (3), which enables changing the gas phase in the exchange zone without changing the composition and state of the sample surface.…”

“…[49][50][51][52][53][54][55][56][57][58], and often lead to significantly different results. 36,40,[50][51][52] Therefore, one of the goals of this work was to compare the results of two relaxation methods: isotope and chemical ones.…”

“…Among them, the most suitable and effective are coulometric titration, 10–16 electrical conductivity relaxation 17–24 and other methods based on relaxation 25–28 and quasi-equilibrium 29,30 approaches, as well as methods using oxygen isotopes to study the exchange rate in non-stationary regimes. 31–41 Several basic models for the data processing are generally accepted 42 and agree that the O 2 transport can be described by two main stages: the dissociation of an O 2 molecule on the oxide surface (surface exchange) or the movement of oxygen atoms in the volume of a solid (bulk diffusion). 43–46…”

“…Among them, the most suitable and effective are coulometric titration, [10][11][12][13][14][15][16] electrical conductivity relaxation [17][18][19][20][21][22][23][24] and other methods based on relaxation [25][26][27][28] and quasi-equilibrium 29,30 approaches, as well as methods using oxygen isotopes to study the exchange rate in non-stationary regimes. [31][32][33][34][35][36][37][38][39][40][41] Several basic models for the data processing are generally accepted 42 and agree that the O 2 transport can be described by two main stages: the dissociation of an O 2 molecule on the oxide surface (surface exchange) or the movement of oxygen atoms in the volume of a solid (bulk diffusion). [43][44][45][46] Such a large variety of methods and their specific implementations provide advantages for studying the oxygen transport parameters under a wide range of conditions in terms of temperature and O 2 partial pressure, as well as significantly different morphologies (powders, compact samples, and membranes of various thicknesses).…”