Structural and defect chemistry guidelines for Sr(V,Nb)O3-based SOFC anode materials

Area of Science:

• Materials Science
• Electrochemistry
• Solid Oxide Fuel Cells (SOFCs)

Background:

• Strontium vanadate (SrVO3-δ) is a promising material for SOFC anodes due to its electrical conductivity.
• However, its application is limited by redox instability and high thermal expansion.
• Niobium substitution is explored to improve the performance and stability of SrVO3-δ.

Purpose of the Study:

• To investigate the structural and defect chemistry of Nb-substituted SrVO3-δ for SOFC anode applications.
• To evaluate the impact of niobium substitution on redox tolerance, thermochemical compatibility, and electrical conductivity.
• To understand how oxygen stoichiometry changes affect electrocatalytic performance.

Main Methods:

• Solid-state synthesis of SrV1-xNbxO3-δ ceramics (x = 0-0.30).
• Sintering at 1773 K in a reducing atmosphere.
• Characterization using X-ray Diffraction (XRD) and Scanning Electron Microscopy with Energy Dispersive Spectroscopy (SEM/EDS).

Main Results:

• A single-phase cubic perovskite structure was achieved up to x ≈ 0.25.
• Electrical conductivity remained metallic-like and high (>100 S cm⁻¹ for x ≤ 0.20), despite a slight decrease with Nb substitution.
• Niobium substitution improved phase stability, shifted the upper p(O2) limit for stability, and significantly reduced thermal expansion (from 22.7 × 10⁻⁶ to 13.3 × 10⁻⁶ K⁻¹).

Conclusions:

• Nb-substituted SrVO3-δ perovskites offer enhanced stability and reduced thermal expansion compared to undoped SrVO3-δ.
• The materials exhibit sluggish oxidation kinetics, leading to nearly reversible behavior in short-term redox cycles.
• Structural and defect chemistry insights provide guidelines for optimizing these materials for SOFC anode applications.