First-principles investigation on the corrosion resistance of rare earth disilicates in water vapor

Rare earth disilicates are used as environmental barrier coatings to prevent the non-oxide silicon-based ceramics from water vapor corrosion at high temperatures. However, existing experimental results about the water vapor corrosion behavior of these materials are scarce and sometimes contradictory. In this paper, we report theoretical studies on the water vapor corrosion resistance of rare earth disilicates using Mulliken analysis based on first-principles. The Mulliken populations of Si-O bonds in Y2Si2O7, Sc2Si2O7, Yb2Si2O7, Lu2Si2O7, and substituted Y2Si2O7 are calculated. The relative water vapor corrosion resistance of these materials is predicted by comparing the values of Mulliken population. The predictions are consistent with the reported experimental data. This work suggests a computational method for design and selection of rare earth disilicate materials for better water vapor corrosion resistance. (C) 2009 Elsevier Ltd. All rights reserved.