Solid oxide fuel cells (SOFCs) offer high efficiency and fuel flexibility, but their widespread application is limited by the high cost and phase instability of state‑of‑the‑art scandia‑stabilized zirconia (ScSZ) electrolytes. In a study published in Frontiers of Chemical Science and Engineering, researchers from Fuzhou University and collaborators present a cost‑effective alternative by partially substituting Sc₂O₃ with Yb₂O₃ in the well‑known 10Sc1CeSZ composition.
The team prepared (Yb₂O₃)ₓ(Sc₂O₃)₀.₁₀₋ₓ(CeO₂)₀.₀₁(ZrO₂)₀.₈₉ (x = 0.04–0.10) electrolyte discs using a coupled tape‑casting and in‑situ solid‑state reaction method. This approach directly uses oxide powders as feedstock, simplifying the process and reducing cost. All Yb₂O₃‑doped electrolytes formed a single cubic phase, eliminating the rhombohedral phase present in undoped 10Sc1CeSZ. With increasing Yb₂O₃ content, the lattice expanded, grain size decreased, and grain boundary resistance dropped—leading to improved conductivity at low temperatures.
The optimized composition, 6Yb4Sc1CeSZ (x = 0.06), achieved an ionic conductivity of 0.088 S·cm⁻¹ at 800 °C and 0.0020 S·cm⁻¹ at 500 °C. Notably, the quaternary Yb₂O₃‑Sc₂O₃‑CeO₂‑ZrO₂ system exhibited higher conductivity and lower activation energy than the ternary Yb₂O₃‑Sc₂O₃‑ZrO₂ system with a comparable Yb₂O₃ amount. The thermal expansion coefficient of the electrolytes increased with Yb₂O₃ content, reaching 13.15 × 10⁻⁶ K⁻¹ for 6Yb4Sc1CeSZ, which better matches the expansion of electrode materials and reduces cracking risks. The bending strength of 10Sc1CeSZ was 217 MPa; after an initial drop at 4 mol% Yb₂O₃, it continuously increased with higher Yb₂O₃ content.
A single cell with a 200‑μm‑thick 6Yb4Sc1CeSZ electrolyte, a Ni‑Gd₀.₂Ce₀.₈O₁.₉ anode, and a La₀.₆Sr₀.₄Co₀.₂Fe₀.₈O₃ cathode delivered a peak power density of 0.65 W·cm⁻² at 800 °C. The cell ran stably for 100 hours at 0.5 A·cm⁻² without noticeable degradation, demonstrating excellent durability.
Yb₂O₃ is priced at only 25–150 USD·kg⁻¹, approximately one‑thirtieth of the cost of Sc₂O₃ (1700–4500 USD·kg⁻¹). This substantial cost reduction, combined with stable cubic phase structure, good conductivity, and robust cell performance, makes the Yb‑doped ScCeSZ electrolyte a promising candidate for commercial SOFCs. The strategy of partial substitution with a larger, cheaper rare‑earth cation offers a practical pathway toward affordable and durable solid oxide fuel cells.
DOI
10.1007/s11705-026-2645-7