Nanostructured Ni‐Based Cathode Materials for Intermediate Temperature SOFC

Abstract

Ni substituted lanthanum strontium manganite, (La_0.8Sr_0.2)_0.95Mn_1‐xNi_xO_3‐δ (x=0–0.5), was synthesized by ceramic route. X‐ray diffraction revealed it to be a single phase up to 40 mole % Ni, but above x=0.4 two phases viz., La₂NiO₄ and NiO start separating out. Even though it was prepared by ceramic route, the crystallite size was found to be ∼20 nm. At 900°C, the rhombohedral phase of LSM could be retained only with very low Ni doping (x≤0.1) and compositions between (La_0.8Sr_0.2)_0.95Mn_0.8Ni_0.2O_3‐δ (LSMNi₂) to (La_0.8Sr_0.2)_0.95Mn_0.6Ni_0.4O_3‐δ (LSMNi₄) were found to have orthorhombic symmetry. At 1400°C, all the compositions showed rhombohedral symmetry. The thermal expansion coefficients (α) in the temperature interval of 20–850°C of (La_0.8Sr_0.2)_0.95MnO_3‐δ, (La_0.8Sr_0.2)_0.95Mn_0.9Ni_0.1O_3‐δ and (La_0.8Sr_0.2)_0.95Mn_0.8Ni_0.2O_3‐δ were 10.08×10⁻⁶ °C⁻¹, 11.82×10⁻⁶ °C⁻¹ and 13.59×10⁻⁶ °C⁻¹, respectively. The thermal and chemical compatability of LSMNi₂ with ceria‐based electrolytes, Ce_0.8Gd_0.2O_1.9 and Ce_0.8Sm_0.2O_1.9 was also studied using XRD and SEM technique.

Keywords:

• (La_0.8Sr_0.2)_0.95Mn_1‐xNi_xO_3‐δ
• X‐ray diffraction
• dilatometry
• compatibility
• SOFC