Oxygen tracer diffusion in dense Ba0.5Sr0.5Co0.8Fe0.2O3−δ films

Abstract

Ba 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3 - δ (BSCF) is an interesting material for high temperature oxygen permeation membranes and solid oxide fuel cell cathodes, applications for which oxygen transport properties are crucial. Here oxygen isotope exchange is performed on dense BSCF films prepared by pulsed laser deposition on MgO single crystal substrates. The oxygen isotope profile is analyzed by secondary ion mass spectrometry to extract tracer diffusion coefficients D∗ and effective surface exchange constants k∗. Tracer diffusion has a low activation energy of 0.5 eV. At moderate temperatures, the related oxygen vacancy diffusion coefficient DVÖ is significantly larger than that for (La,Sr)(Fe,Co)O3−δ perovskites.

High temperature X-ray diffraction and thermo-gravimetrical analysis of the cubic perovskite Ba0.5Sr0.5Co0.8Fe0.2O3−δ under different atmospheres

“…Since the first report on BSCF there has been a tremendous effort to study the superior transport properties and ionic conductivity of BSCF and related materials [9][10] . Low vacancy formation energy and low activation barrier for vacancy diffusion accounts for high oxygen vacancy concentration and high ionic mobility in BSCF 11 . The material exhibits very high oxygen permeation flux over a considerable temperature range.…”

Oxygen Transport Kinetics of Mixed Ionic-Electronic Conductors by Coupling Focused Ion Beam Tomography and Electrochemical Impedance Spectroscopy

“…42 For the same electrochemically active thickness, BSCF presents a higher k δ value than LSCF, due to the larger amount of oxygen vacancies, so that even a coarser microstructure shows higher performance. More interestingly, the surface-exchange coefficients calculated for 11 and for bulk samples from Bucher et al 5 (converted according to k δ = γ · k * ). The chemical surface-exchange coefficient (k δ ) for thin-films from Burriel et al 10 and Asano et al 9 and for bulk samples from Bucher et al, 5 Ried et al 4 and Girdauskaite et al 6 are also given as comparison.…”

“…17 The k * values obtained by tracer experiments for BSCF thin-films 11 and by ECR measurements for BSCF bulk samples calculated applying the thermodynamic factor, 5 are shown as comparison. Meanwhile, Figure 8b shows the k * values of BSCF at pO 2 from 0.02 to 0.21 atm at T = 700…”

“…[1][2][3] The surface-exchange coefficient (k) and the oxygen diffusion coefficient (D) provide key information about the oxygen transport mechanism that dominates the cathodic ORR. Many publications have assessed the D and k values of MIEC materials, most commonly by; electrical conductivity relaxation (ECR) measurements for dense bulks [4][5][6][7][8] or thin-films 9,10 (k δ , D δ ) and by oxygen tracer diffusion experiments for thin-films 11 or powder 12 (k * , D * ). The oxygen transport parameters are usually determined by ex situ experiments for model systems (i.e.…”

Molecular dynamics analysis of lattice site dependent oxygen ion diffusion in YBa2Cu3O7−δ: Exposing the origin of anisotropic oxygen diffusivity

“…Attention has therefore focused on the diffusivity of oxygen in solid state oxides [3][4][5][6][7][8][9][10][11]. Some high temperature superconductors, such as yttrium-barium cuprate (YBa 2 Cu 3 O 7−δ or YBCO), with quite promising superconductive and magnetic properties [12,13], are one case where both the oxide crystal growth and phase transitions are highly sensitive to oxygen diffusion.…”