Oxygen Mobility in Compositional Variants of Mayenite

Area of Science:

• Materials Science
• Solid-state Chemistry
• Computational Materials Science

Background:

• Mayenite (Ca₁₂Al₁₄O₃₃) features a positively charged framework with mobile anions.
• Isostructural compounds Ca₁₂Ga₁₄O₃₃ and Sr₁₂Al₁₄O₃₃ possess larger cages due to cation substitution, suggesting altered ion transport properties.

Purpose of the Study:

• To investigate and compare oxygen ion mobility in Ca₁₂Al₁₄O₃₃, Ca₁₂Ga₁₄O₃₃, and Sr₁₂Al₁₄O₃₃.
• To elucidate the influence of framework cations (Ca, Ga, Sr) and cage size on oxygen diffusion pathways.

Main Methods:

• Classical molecular dynamics simulations were employed.
• Simulations were conducted at various temperatures: 77 K, 300 K, 700 K, and 1673 K.
• Analysis focused on oxygen ion movement and diffusion mechanisms within the crystal structures.

Main Results:

• Oxygen ion mobility differs significantly among the studied compounds.
• Ca₁₂Ga₁₄O₃₃ exhibits oxygen movement primarily through caged and framework oxygen exchange.
• Ca₁₂Al₁₄O₃₃ shows mobility via combined exchange and passage through cage windows, while Sr₁₂Al₁₄O₃₃ demonstrates limited oxygen mobility.

Conclusions:

• The cation composition critically influences oxygen ion diffusion pathways and rates in these mayenite-related structures.
• Understanding these transport mechanisms is crucial for potential applications in areas requiring ion conductivity.
• Sr₁₂Al₁₄O₃₃ appears less suitable for applications demanding high oxygen mobility compared to its Ca-based counterparts.