Phase evolution and thermal stability of novel high-entropy (Mo0.2Nb0.2Ta0.2V0.2W0.2)Si2 ceramics.

Owing to the high melting points and high-temperature stability, transition-metal disilicides are potential components for aerospace, automotive, and industrial engineering applications. However, unwanted oxidation known as PEST oxidation severely limits their application owing to the formation of volatile transition metal oxides, especially in the temperature range of 500–1000 °C. To overcome this problem, a new class of high-entropy disilicides, (Mo 0.2 Nb 0.2 Ta 0.2 V 0.2 W 0.2)Si 2 , was selected by first-principles calculations and then successfully fabricated using a hot-pressing sintering technique. Furthermore, the phase evolution, thermal expansion behavior, thermal conductivity, and oxidation behavior were systematically investigated. Compared with MoSi 2 , (Mo 0.2 Nb 0.2 Ta 0.2 V 0.2 W 0.2)Si 2 possessed a lower thermal conductivity (10.9–14.7 W·m−1·K−1) at 25–1000 °C, higher thermal expansion coefficients (8.6 ± 1.3–6 K–1) at 50–1200 °C, and especially an excellent thermal stability at 500–1000 °C owing to slow diffusion and selective oxidation. This work provides a strong foundation for the synthesis and application of high-entropy disilicides. [ABSTRACT FROM AUTHOR]