The effect of B‐site Y substitution on cubic phase stabilization in (Ba_0.5Sr_0.5)(Co_0.8Fe_0.2)O_3−δ

Abstract

The cubic phase mixed ionic-electronic conductor (Ba 0.5 Sr 0.5 )(Co 0.8 Fe 0.2 )O 3−δ (BSCF) is well-known for its excellent oxygen ion conductivity and high catalytic activity. However, formation of secondary phases impedes oxygen ion transport and consequentially a widespread application of BSCF as oxygen transport membrane. B-cation substitution by 1, 3 and 10 at.% Y was employed in this work for stabilization of the cubic BSCF phase. Secondary phase formation was quantified on bulk and powder samples exposed to temperatures between 640 and 1100°C with annealing time up to 44 days. The phase composition, cation valence states, and chemical composition of all samples were analyzed by high-resolution analytical electron microscopic techniques. Y doping effectively suppresses the formation of Ba n+1 Co n O 3n+3 (Co 8 O 8 ) (n ≥ 2) and Co x O y phases which would otherwise act as nucleation centers for the highly undesirable hexagonal BSCF phase. This work validates for 10 at.% Y cation substitution perfect stabilization of the cubic BSCF phase at temperatures ≥800°C, while a negligible small volume fraction of the hexagonal BSCF phase was found at lower temperatures. A newly developed model describes the effect of Y doping on the formation of secondary phases and their effective suppression with increasing Y concentration. K E Y W O R D SBSCF, energy dispersive X-ray spectroscopy, oxygen transport membrane, transmission electron microscopy, Y-doping

Comparative performance assessment of nano-composite cathode of LMSO-BSCMF for low temperature solid oxide fuel cell applications

“…From the works of Zeng et al [18], doping the BSCF cathode with Zn was found to be influential to increase the electrocatalytic activity. The BSCF system was also doped with Mo6+, Nb3+ and Y3+ ions and improved cell performance was demonstrated [19][20][21]. In our earlier work, doping Mg along with Co was also found to be promising in enhancing the cell performance [22].…”

Effect of cobalt and magnesium doping on the performance of Ba0.5Sr0.5Fe0.8O3 cathode for solid oxide fuel cell applications

“…Zeng et al [24] doped Zn in the BSCF cathode material and enhanced electrocatalytical activity has been observed. Similarly, several other ions including Mo 6+ , Nb 3+ and Y 3+ were also doped into the BSCF system and the performance of the fuel cell was assessed and results were found to be interesting [25][26][27].…”

A Zn-Doped Ba0.5Sr0.5Co0.8Fe0.2O3-δ Perovskite Cathode with Enhanced ORR Catalytic Activity for SOFCs

“…Nevertheless, to assure the practical applications of BSCF cathode, the chemical and structural instabilities at intermediate temperatures is a crucial issue that needs to be addressed [4,23]. Several groups has attempted to obtain the stable cubic crystal structure of BSCF by partially substituting the reducible B-site Fe and Co ions with less reducible or constant valence metal ions (e.g., Mo 6+ , Nb 3+ , Zr 4+ , Y 3+ ) [24][25][26][27][28][29][30]. The B-site Zn-doping was also found to stabilize the cubic perovskite oxides, e.g., Ba 0.5 Sr 0.5 Zn 0.2 Fe 0.8 O 3−δ and BaCo 0.4 Fe 0.4 Zn 0.2 O 3-δ , thus conferring stable long-term oxygen permeability and CO 2 -resistance for the derived ceramic membranes [28,31].…”