The p(O-2)-T stability domain of cubic perovskite Ba0.5Sr0.5Co0.8Fe0.2O3-delta

authors	Yaremchenko, AA; Patrakeev, MV; Naumovich, EN; Khalyavin, DD
nationality	International
journal	PHYSICAL CHEMISTRY CHEMICAL PHYSICS
keywords	OXIDE FUEL-CELLS; SECONDARY PHASE-FORMATION; OXYGEN PERMEATION; INTERMEDIATE TEMPERATURES; BSCF PEROVSKITE; DOPED BA0.5SR0.5CO0.8FE0.2O3-DELTA; ELECTRICAL-PROPERTIES; NEUTRON-DIFFRACTION; CHEMICAL-STABILITY; GRAIN-SIZE
abstract	Cubic perovskite-type Ba0.5Sr0.5Co0.8Fe0.2O3-delta (BSCF) is one of the mixed ionic-electronic conductors with the highest oxygen permeability known to date. It serves as a parent material for the development of functional derivatives for electrochemical applications including oxygen separation membranes, solid electrolyte cell electrodes and electrocatalysts for the oxygen evolution reaction. The present study is focused on the determination of the precise stability boundaries of cubic perovskite BSCF employing a coulometric titration technique in combination with thermogravimetric analysis, X-ray and neutron diffraction, and molecular dynamics simulations. Both the low-p(O-2) and high-p(O-2) stability boundaries at 700-950 degrees C were found to correspond to a fixed value of oxygen content in the perovskite lattice of 3 - delta = similar to 2.13 and similar to 2.515, respectively. The stability limits in this temperature range are expressed by the following equations: high-p(O-2) boundary: log p(O-2) (atm) (+/- 0.1) = -10 150/T (K) + 8.055; low-p(O-2) boundary: log p(O-2) (atm) (+/- 0.03) = -20 750/T (K) + 4.681. The p(O-2)-T phase diagram of the BSCF system under oxidizing conditions is addressed in a wider temperature range and is shown to include a region of precipitation of a "low-temperature'' phase occurring at 400-500 degrees C. The fraction of the low-temperature precipitate, which co-exists with the cubic perovskite phase and is stable up to 790-820 degrees C, increases upon increasing p(O-2) in the range 0.21-1.0 atm.
publisher	ROYAL SOC CHEMISTRY
issn	1463-9076
year published	2018
volume	20
issue	6
beginning page	4442
ending page	4454
digital object identifier (doi)	10.1039/c7cp07307k
web of science category	Chemistry, Physical; Physics, Atomic, Molecular & Chemical
subject category	Chemistry; Physics
unique article identifier	WOS:000424357100062