High-entropy engineering promotes the thermal properties of monosilicates

It is difficult to obtain X2-type rare-earth monosilicates that have the advantages of low thermal conductivity and a thermal expansion coefficient that matches that of ceramic matrix composites, and thus, the efficient use of these materials in extreme environments is challenging. In this study, we developed a novel component regulation method, which significantly reduced thermal conductivity and helped achieve a suitable thermal expansion coefficient for monosilicates. Monosilicates have low thermal diffusion coefficients mainly due to the effect of extrinsic phonon scattering mechanisms. We analyzed different extrinsic phonon scattering mechanisms associated with point defect, disorder, grain boundary, lattice distortion, dislocation, and symmetry.