Interfacial oxide wedging for mechanical-robust electrode in high-temperature ceramic cells.

Area of Science:

• Materials Science
• Electrochemistry
• Ceramic Engineering

Background:

• Degradation of high-temperature electrochemical ceramic cells is often caused by air electrode delamination and cracking.
• Compositing negative thermal expansion (NTE) materials can reduce delamination but may worsen cracking due to thermal stress between NTE and positive thermal expansion perovskites (PTE).

Purpose of the Study:

• To develop a strategy for enhancing the mechanical robustness and durability of air electrodes in high-temperature electrochemical cells.
• To mitigate cracking in air electrodes by introducing interfacial oxides that "wedge" the NTE-PTE interface.

Main Methods:

• Compositing NTE material HfW2O8 with perovskite Ba0.5Sr0.5Co0.8Fe0.2O3-δ.
• Utilizing reactive calcination at near-melting temperatures to form interfacial wedging oxides (Co3O4, Fe3O4, BaHfO3, Sr3WO6).
• Characterizing the mechanical properties (bulk modulus, hardness) and thermal expansion coefficient (TEC) of the composite air electrodes.

Main Results:

• Simultaneous enhancement of bulk modulus (102%) and hardness (138%) was achieved.
• Mitigated TEC by 35%, reducing thermal stress.
• Demonstrated enhanced durability over 40 thermal cycles (600°C to 300°C) with no decay after two years of ambient air exposure.

Conclusions:

• The introduction of interfacial oxides effectively prevents cracking within the air electrode bulk.
• This method provides a viable strategy for creating mechanically robust electrodes for high-temperature electrochemical applications.
• The developed air electrodes exhibit superior long-term stability and resistance to mechanical degradation.