First-principles study on surface and internal hydrogen diffusion of Y₂O₃

Area of Science:

• Materials Science
• Surface Science
• Hydrogen Embrittlement

Background:

• Yttrium oxide (Y2O3) is a crucial coating material for preventing hydrogen permeation in alloys.
• Limited research exists on the performance and hydrogen interaction mechanisms of Y2O3 coatings under hydrogen exposure.

Purpose of the Study:

• To investigate hydrogen adsorption and diffusion mechanisms within Y2O3.
• To elucidate the role of surface oxygen vacancies in hydrogen permeation through Y2O3 coatings.

Main Methods:

• Density Functional Theory (DFT) calculations were employed to model hydrogen adsorption and diffusion on Y2O3 surfaces.
• Surface energy calculations identified the most stable Y2O3 surface termination (O-layer).
• Migration energy barriers for hydrogen diffusion were computed, considering interstitial sites and vacancies.

Main Results:

• The O-layer terminated Y2O3 surface is energetically favorable.
• Unsaturated oxygen atoms on the surface facilitate hydrogen adsorption.
• Surface oxygen vacancies act as crucial intermediate sites, lowering the energy barrier for hydrogen diffusion into the Y2O3 bulk.
• Hydrogen diffusion pathways were identified through octahedral and tetrahedral interstitial sites.
• Calculated hydrogen diffusion coefficients and permeability closely match experimental data.

Conclusions:

• Surface oxygen vacancies significantly enhance hydrogen diffusion into Y2O3.
• Understanding these mechanisms provides a theoretical basis for designing more effective Y2O3 coatings with improved hydrogen resistance.
• The findings contribute to mitigating hydrogen embrittlement in alloys utilizing Y2O3 protective layers.