Enhanced oxygen diffusivity in interfaces of nanocrystalline ZrO2.Y2O3

Area of Science:

• Materials Science
• Solid State Chemistry
• Nanotechnology

Background:

• Yttria-doped zirconia (ZrO2) is a key material in solid oxide fuel cells and oxygen sensors.
• Understanding oxygen diffusion in nanostructured ceramics is crucial for optimizing their performance.
• Grain boundary diffusion can significantly impact overall material transport properties.

Purpose of the Study:

• To measure oxygen grain boundary diffusion coefficients in nanocrystalline yttria-doped zirconia (n-ZrO2).
• To compare oxygen diffusion rates in n-ZrO2 with those in single-crystal ZrO2.
• To determine the temperature dependence of oxygen grain boundary diffusivity and surface exchange coefficients.

Main Methods:

• Secondary ion mass spectrometry (SIMS) was used to measure (18)O diffusion profiles.
• Nanocrystalline yttria-doped ZrO2 specimens and single crystals were utilized for diffusion experiments.
• Diffusion coefficients were extracted from the measured concentration profiles.

Main Results:

• Oxygen diffusion profiles in n-ZrO2 were substantially deeper than in single crystals.
• Oxygen diffusivity in the grain boundaries (D(B)) was found to be approximately three orders of magnitude higher than in single crystals.
• Temperature-dependent equations for D(B) and the oxygen surface exchange coefficient (k) were derived.

Conclusions:

• Grain boundaries in n-ZrO2 act as fast diffusion pathways for oxygen.
• The enhanced oxygen diffusivity in grain boundaries is critical for applications requiring rapid oxygen transport.
• The derived diffusion and exchange coefficients provide valuable data for modeling and designing ZrO2-based devices.