Thermomechanical properties of rare earth phosphates as environmental barrier coatings

Abstract This study integrated high‐throughput computational modeling with experimental validation to investigate rare earth (RE) phosphates as potential environmental barrier coatings (EBCs) for SiC‐based ceramic matrix composites (CMCs). Although RE silicates have been widely studied for EBC applications, they are prone to degradation due to water vapor corrosion and silica volatilization at high temperatures. RE phosphates, with their strong P–O bonds, offer a promising alternative with improved resistance to volatilization. Using the AFLOW computational framework, we performed density functional theory calculations to evaluate the thermomechanical properties of single‐component RE phosphates. Specifically, AFLOW Automatic Elasticity Library (AEL) was employed to predict mechanical properties, and AFLOW Automatic GIBBS Library (AGL) and AFLOW Quasiharmonic Approximation (QHA) were used to estimate thermal properties. Our results indicate that although the AGL method performs well in predicting thermal conductivity, it may not be suitable for screening the coefficient of thermal expansion of RE phosphates. Additionally, we explored the concept of configurational disorder in high‐entropy phosphates to enhance their thermal performance. Our experimental validation supported the computational findings, demonstrating that incorporating multiple RE elements into phosphates can significantly improve the performance of EBCs for SiC‐based CMCs.