A density functional study of defect migration in gadolinium doped ceria

Area of Science:

• Materials Science
• Computational Materials Science
• Electrochemistry

Background:

• Doped ceria shows significantly higher oxygen ion conductivity than yttria-stabilized zirconia below 600°C.
• Gadolinium doped ceria (GDC) is a leading candidate for solid electrolyte applications in solid oxide fuel cells (SOFCs) operating at intermediate temperatures.
• Understanding atomic defect migration is crucial for optimizing GDC's performance.

Purpose of the Study:

• To investigate atomic defect migration, specifically oxygen vacancy movement, in Gadolinium doped ceria (GDC).
• To determine the activation energies for various oxygen vacancy formation and migration pathways.
• To identify the most favorable sites and pathways for oxygen vacancy migration relative to Gd dopant ions.

Main Methods:

• Employed total energy calculations using density functional theory (DFT).
• Analyzed oxygen vacancy formation and migration energies at different neighbor positions relative to Gd dopant ions.
• Compared calculated activation energies with existing literature data.

Main Results:

• The first nearest neighbor site to the Gd(3+) dopant ion is the most favorable for oxygen vacancy formation due to similar ionic radii.
• The most favorable migration pathway involves an oxygen vacancy moving from a second to a first nearest neighbor site.
• Calculated activation energies are consistent with reported experimental and computational values.

Conclusions:

• DFT calculations provide insights into oxygen vacancy migration mechanisms in GDC.
• The findings identify key sites and pathways influencing oxygen ion conductivity in doped ceria.
• This study lays the groundwork for developing kinetic lattice Monte Carlo models to further understand vacancy diffusion and enhance GDC-based SOFCs.