Investigation of thermal properties of rare-earth X2-Type monosilicates through high-entropy design and defect engineering

Rare earth X2-type monosilicates with low thermal conductivity are crucial for material performance in extreme environments. Three high-entropy ceramics, (Er 1/4 Tm 1/4 Yb 1/4 Lu 1/4 ) 2 SiO 5 , (Y 1/4 Er 1/4 Tm 1/4 Yb 1/4 ) 2 SiO 5 , and (Gd 1/4 Dy 1/4 Er 1/4 Yb 1/4 ) 2 SiO 5 , were synthesized in this study. Among these, the thermal conductivity of (Y 1/4 Er 1/4 Tm 1/4 Yb 1/4 ) 2 SiO 5 at 1200 °C is 1.03 W m −1 K −1 . Concurrently, the stable existence of dislocation arrays was observed in the quaternary high-entropy monosilicate system of (Y 1/4 Er 1/4 Tm 1/4 Yb 1/4 ) 2 SiO 5 . The scattering of medium-frequency phonons can be enhanced by the presence of dislocations, leading to a reduction in thermal conductivity. This provides direct experimental evidence supporting the feasibility of reducing material thermal conductivity through high-entropy design by introducing dislocations.