Ab initio simulations of M2AX (M = lanthanides, A = Al or Si, X = C or N) phases as bond coats for thermal barrier coatings

Abstract

MAX phases such as Ti2AlC and Cr2AlC are attracting attention due to their oxides (Al2O3 or Cr2O3). However, little research has considered MAX phases incorporating rare earth elements at the M sites. This study used ab initio calculations to explore the temperature dependence of the Young's modulus and coefficient of thermal expansion (CTE) of MAX phases with M = La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, or Lu. MAX phases with M = Er, Lu, and Tm are particularly suitable for use as a bond coat (BC) layer between a thermally grown oxide (TGO) and substrate, given the compatibility of thermal expansion. The low CTE difference between a MAX phase and the TGOs or substrate can effectively relieve thermal stresses. These findings provide valuable insights into the development of MAX phase BCs.