Heat radiation mitigation in rare-earth pyrosilicate composites: A first principles investigation of refractive index mismatch

Abstract

Thermal radiation emission poses a challenge for using most existing ceramics for thermal environmental barrier coatings of gas-turbine engines operating at temperatures approaching 1500 °C and beyond. This study presents a strategy for photon transport mitigation in fully dense ceramic composites by increasing the refractive index mismatch between the matrix and particle oxides. We investigate this strategy by analyzing radiative properties in 118 different rare-earth pyrosilicate–pyrochlore ceramic composites. We use density functional theory to predict the optical properties of homogeneous oxides and Lorentz–Mie theory to model scattering at the interfaces of the composite. Our findings demonstrate that increasing the refractive mismatch between the matrix and oxide phases can significantly reduce radiative heat flux. Furthermore, we show that additional thermal radiation suppression can be achieved by increasing the particle size. Our theoretical investigation has the potential to aid in the discovery of new coating ceramic composites and guide their microstructural design.