Environmental effects on degradation behavior in YbGdSi ternary system at elevated temperatures

Degradation of Yb–Gd–Ti-Si middle entropy silicides in oxidizing atmosphere

“…Unfortunately, the weight gain and oxidation rate of these silicides depend on the oxides formed on their surfaces, and it is difficult to extract the effect of the mixed entropy on the oxidation behavior. As discussed previously [18], the formation of complex oxides containing Yb-Gd-Si-O (and Yb-Gd-Ti-Si-O) acts as a barrier for oxygen diffusion into the unoxidized area, and similar mechanisms have been reported in studies on the oxidation mechanism of mid-and high-entropy materials [20][21][22].…”

“…Because compounds in Gd-Si systems also have higher melting points than Si, Morigayama et al studied the phase stability of Yb 25 Gd 20 Si 55 ternary silicides at high temperatures (1500 °C) using a calculated phase diagram (CALPHAD) to improve the phase stability [17] The results proved that the addition of Gd prevents oxidation, and the Yb-Si phase stability improves because no liquid phase is formed and the weight gain is suppressed at up to ∼1200 °C [17,18]. However, at between 700 °C and 900 °C, a rapid weight gain has been observed owing to the formation of Yb 2 O 3 , leading to the preferential oxidation of the grain boundaries, which is still a critical issue in Yb-silicides and Yb-Gd-Si systems.…”