The effect of microstructure on the deuterium permeation inhibition properties of Er2O3 coatings was investigated. Coatings were prepared by metal organic chemical vapor deposition (MOCVD) followed by annealing at 700 degrees C or 800 degrees C. The coating annealed at 700 degrees C exhibited a more compact structure than the as-deposited coating and the coating annealed at 800 degrees C. The hydrogen permeation inhibition performance of coatings was investigated by deuterium permeation measurement. The most compact 700 degrees C-prepared coating also exhibited the best permeation inhibition performance. Furthermore, large cracks and holes appeared on the coating annealed at 800 degrees C after the permeation measurement, suggesting too high annealing temperature could result in more structural defects, leading to poorer mechanical integrity and inhibition performance. X-ray photoelectron spectroscopic analysis indicated that the oxygen/erbium ratio of the coating annealed at 700 degrees C corresponded closely to the stoichiometric ratio. Copyright (C) 2015, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.