Silicon carbide-based ceramic matrix composites (SiC/BN/ SiC CMCs) entered service in the hot section of civilian aircraft turbine engines in 2016. 1 The use of CMCs allows for both a reduction in weight and an increase in operating temperature relative to the nickel-base superalloys that are currently employed, leading to lower emissions and greater engine efficiency. 1,2 SiC oxidizes to form silica (SiO 2 ) and carbon monoxide gas (CO). Silica volatilizes in the presence of water, a byproduct of the fuel combustion process, resulting in unacceptable rates of material loss (Equation 1). 3,4 Environmental barrier coatings (EBCs) are employed to limit the reaction between CMCs and water vapor. Stateof-the-art EBCs are based on rare earth silicate systems,(1) SiO 2 (s) + 2H 2 O (g) → Si(OH) 4 (g)