The electronic conductivity of Ba0.5Sr0.5Co x Fe1−x O3−δ (BSCF: x = 0 ∼ 1.0) under different oxygen partial pressures

Abstract

The electronic conductivity of sintered BSCF ceramics (Ba 0.5 Sr 0.5 Co x Fe 1−x O 3−δ , 0≤x≤1) was measured as a function of temperature up to 1273 K in air. The conductivity of BSC is thermally activated over 298-1273 K with an activation energy of 0.21 eV. The conductivity of BSF and BSCF (0.2≤x≤0.8) is thermally activated below ∼673 K with activation energies of 0.21 eV-0.40 eV. Above 673 K, the formation of oxygen vacancies results in a decrease in p-type carrier concentration and a decrease in electronic conductivity. Ba 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3−δ (BSCF5582) was also measured under 10 −5 atm≤pO 2 ≤1 atm. Below ∼673 K, the electronic conductivity of BSCF 5582 shows no dependence on pO 2 . Above 673 K, the conductivity of BSCF5582 increases with increasing pO 2 for pO 2 ≥0.01 (p-type conduction) and decreases slightly with increasing pO 2 for pO 2 ≤0.01 atm. The activation energy for conduction above ∼673 K and at pO 2 ≥0.1 is ∼0.07 eV. Above ∼823K and at pO 2 ≥0.01 atm, the activation energy for conduction is ∼0.2 eV.

Processing and oxygen permeation studies of asymmetric multilayer Ba0.5Sr0.5Co0.8Fe0.2O3− membranes

“…XRD analysis confirmed the formation of single-phase cubic perovskite-type structure for the BSCF and SCF ceramics after sintering, with the lattice parameters of 0.3987 ± 0.0001 nm and 0.3865 ± 0.0001 nm (space group: Pm3m), respectively, in agreement with the literature data [9,26]. Typical SEM micrograph of the sintered and fractured BSCF membrane is shown in Fig.…”

“…4. The materials, prepared in present work, demonstrate similar absolute values and trends of the conductivity behavior with temperature and composition of A-sublattice if compared to the literature data [12,26,30]. Under oxidizing conditions, the total conductivity of BSCF and SCF at 973-1223 K decreases with reducing partial oxygen pressure, whilst the Seebeck coefficient has a positive sign and increases at p(O 2 ) > 10 3 Pa (Fig.…”

“…5). This confirms that p-type electronic transport dominates under these conditions [12,26,30]. The Seebeck coefficient of BSCF passes through a maximum at p(O 2 ) ∼ 10 2 -10 3 Pa, for SCF the corresponding maximum is shifted to the lower oxygen partial pressure.…”

Kinetic demixing/decomposition of Ba0.5Sr0.5Co Fe1−O3− (x= 0.2 and 0.8)

“…The calculated Joule heat (W) for BSCF5582 and BSCF5528 under 7 A/cm 2 at 1000 • C and pO 2 = 10 −5 atm are 0.26 W and 27.67 W, respectively. 21 This means that the frameworks of O B O in the perovskite structure of BSCF5528 are more unstable and easily broken due to high Joule heat, allowing the Co cations to migrate, even though Schematic diagram for the phase composition stability between before applied current and during applied current as a function of pO 2 at 1000 • C (σ i,5582 = ionic conductivity of BSCF5582, σ i,5528 = ionic conductivity of BSCF5528, σ i = σ i,5582 − σ i,5528 , σ t,5582 = total conductivity of BSCF5582, σ t,5528 = total conductivity of BSCF5528, σ t = σ t,5582 − σ t,5528 and x = cobalt concentration). the application temperature is 150 • C lower than the congruent melting temperature of 1150 • C. 17,18 The severe grain growth was observed in both sides of BSCF5528, as shown in Fig.…”

“…21 The starting materials consist of barium nitrate (Ba(NO 3 ) 2 , ≥99.0% purity, Alfar Aesar Co.), strontium nitrate (Sr(NO 3 ) 2 , ≥99.0% purity, Aldrich Chemical Co.), cobalt(II) nitrate (Co(NO 3 ) 2 ·6H 2 O, ≥99.0% purity, Alfar Aesar Co.), and iron(III) nitrate (Fe(NO 3 ) 3 ·9H 2 O, ≥98.0% purity, Alfar Aesar Co.). A 0.04 mol of ethylenediamine tetraacetic acid (EDTA) was mixed with 40 ml of a 1 M NH 4 OH solution to make a NH 4 -EDTA buffer solution.…”