TY - JOUR

T1 - Crystal structure, electronic conductivity and oxygen exchange kinetics of high-entropy perovskites La0.2Pr0.2Nd0.2Sm0.2Sr0.2Co1-xFexO3-δ (x = 0, 0.5, 1)

AU - Pretschuh, Patrick

AU - Egger, Andreas

AU - Bucher, Edith

N1 - Publisher Copyright: © 2024 Elsevier B.V.

PY - 2024/9/25

Y1 - 2024/9/25

N2 - High-entropy perovskites (HEPs) are attracting increasing attention as air electrode materials for solid oxide cells (SOCs). In this work, three different HEPs from the series La 0.2Pr 0.2Nd 0.2Sm 0.2Sr 0.2Co 1-xFe xO 3-δ (x = 0, 0.5, 1) are synthesized using the citric acid-ethylenediaminetetraacetate (EDTA) method. X-ray diffraction analysis finds crystal structures with the orthorhombic space group 62 (Pnma) at room temperature. The lattice distortion increases with increased Fe-substitution at the B-site. The electrical conductivity (σ e) is determined at temperatures from 600 to 850 °C and oxygen partial pressures (pO 2) between 0.001 and 0.15 bar. For the pure cobaltate, σ e is 1469 S cm −1 at 800 °C and 0.15 bar pO 2. The conductivity is significantly reduced with Fe-doping, reaching 87 S cm −1 for the pure ferrate at 800 °C. The chemical oxygen surface exchange coefficient (k chem) and the chemical oxygen diffusion coefficient (D chem) are determined by the electrical conductivity relaxation technique. D chem is found to be quite independent of B-site doping and pO 2, with values of approx. 5 × 10 −6 cm 2 s −1 at 800 °C. In contrast, k chem is strongly influenced by the B-site composition, which results in an increase of more than one order of magnitude from the ferrate (3.4 × 10 −5 cm s −1) to the cobaltate (7.7 × 10 −4 cm s −1) at 800 °C and 0.001 bar pO 2. This clearly demonstrates the beneficial effects of Co on the electronic conductivity as well as on the catalytic activity for the oxygen surface exchange reaction.

AB - High-entropy perovskites (HEPs) are attracting increasing attention as air electrode materials for solid oxide cells (SOCs). In this work, three different HEPs from the series La 0.2Pr 0.2Nd 0.2Sm 0.2Sr 0.2Co 1-xFe xO 3-δ (x = 0, 0.5, 1) are synthesized using the citric acid-ethylenediaminetetraacetate (EDTA) method. X-ray diffraction analysis finds crystal structures with the orthorhombic space group 62 (Pnma) at room temperature. The lattice distortion increases with increased Fe-substitution at the B-site. The electrical conductivity (σ e) is determined at temperatures from 600 to 850 °C and oxygen partial pressures (pO 2) between 0.001 and 0.15 bar. For the pure cobaltate, σ e is 1469 S cm −1 at 800 °C and 0.15 bar pO 2. The conductivity is significantly reduced with Fe-doping, reaching 87 S cm −1 for the pure ferrate at 800 °C. The chemical oxygen surface exchange coefficient (k chem) and the chemical oxygen diffusion coefficient (D chem) are determined by the electrical conductivity relaxation technique. D chem is found to be quite independent of B-site doping and pO 2, with values of approx. 5 × 10 −6 cm 2 s −1 at 800 °C. In contrast, k chem is strongly influenced by the B-site composition, which results in an increase of more than one order of magnitude from the ferrate (3.4 × 10 −5 cm s −1) to the cobaltate (7.7 × 10 −4 cm s −1) at 800 °C and 0.001 bar pO 2. This clearly demonstrates the beneficial effects of Co on the electronic conductivity as well as on the catalytic activity for the oxygen surface exchange reaction.

KW - Crystal structure

KW - Electronic conductivity

KW - High-entropy perovskite

KW - Lattice distortion

KW - Oxygen exchange kinetics

KW - Solid oxide cell

UR - http://www.scopus.com/inward/record.url?scp=85204673427&partnerID=8YFLogxK

U2 - 10.1016/j.ssi.2024.116705

DO - 10.1016/j.ssi.2024.116705

M3 - Article

VL - 417.2024

JO - Solid State Ionics

JF - Solid State Ionics

SN - 0167-2738

IS - December

M1 - 116705

ER -