Robust hydrophobicity and evaporation inertness of rare‐earth monosilicates in hot steam at very high temperature

Rare‐earth oxides are intrinsically hydrophobic, and this characteristic opens new horizons for their design and diverse applications as robust hydrophobic surfaces. Here, we discover some rare‐earth (RE) monosilicates (RE 2 SiO 5 ) that are hydrophobic under ambient conditions. Their hydrophobicity is positively correlated with their hot‐steam corrosion at 1400°C. RE 3+ in RE 2 SiO 5 is further found to be a hydration prohibitor, and its species can regulate hydration and volatilization at very high temperatures. These results may provide basis for innovative designs of RE silicates in harsh hot‐steam environments for robust environmental barrier coatings (EBC) or as ceramic components.