Promising La₂Mo₂O₉-La₂Mo₃O₁₂ Composite Oxygen-Ionic Electrolytes: Interphase Phenomena

Area of Science:

• Materials Science
• Solid State Chemistry
• Electrochemistry

Background:

• Lanthanum molybdate oxides are key materials for solid oxide fuel cells.
• Understanding ion transport in composite oxides is crucial for improving electrochemical device efficiency.

Purpose of the Study:

• To investigate the oxygen-ion conductivity of novel (100 - x)La₂Mo₂O₉-xLa₂Mo₃O₁₂ composite materials.
• To explore the relationship between microstructure, phase formation, and ionic conductivity in these composites.

Main Methods:

• Synthesis and characterization of (100 - x)La₂Mo₂O₉-xLa₂Mo₃O₁₂ composites with varying compositions (x = 5, 10, 15, 20, 30, 100).
• Measurement of electrical conductivity, oxygen surface exchange coefficient, and oxygen diffusivity.
• 3D-modeling of composite microstructure using SEM image analysis to estimate interphase layer conductivity.

Main Results:

• Composites exhibited significantly increased oxygen-ion conductivity, oxygen surface exchange, and oxygen diffusivity compared to individual oxides.
• A new La₅Mo₃O₁₆ phase formed at the grain boundaries, facilitating enhanced ion transport.
• 3D-simulated conductivity values correlated well with experimentally measured conductivity, confirming a composite effect.

Conclusions:

• The La₂Mo₂O₉-La₂Mo₃O₁₂ composites are promising for applications requiring high oxygen-ion conductivity.
• The formation of the La₅Mo₃O₁₆ interphase layer is critical for the enhanced performance of these composite materials.