Mechanical Properties and Thermal Conductivity of Y-Si and Gd-Si Silicides: First-Principles Calculations

Abstract

The traditional Si bonding layer in environmental barrier coatings has a low melting point (1414 °C), which is a significant challenge in meeting the requirements of the next generation higher thrust-to-weight ratio aero-engines. To seek new bonding layer materials with higher melting points, the mechanical properties of Y-Si and Gd-Si silicides were calculated by the first-principles method. Subsequently, empirical formulae were employed to compute the sound velocities, Debye temperatures, and the minimum coefficients of thermal conductivity for the YSi, Y5Si4, Y5Si3, GdSi, and Gd5Si4. The results showed that Y5Si4 has the best plasticity and ductility among all these materials. In addition, Gd5Si4 has the minimum Debye temperature (267 K) and thermal conductivity (0.43 W m−1 K−1) compared with others. The theoretical calculation results indicate that some silicides in the Y-Si and Gd-Si systems possess potential application value in high-temperature bonding layers for thermal and/or environmental barrier coating.