SiO2–Yb2O3 Layer as a Diffusion Barrier at the MoSi2/Nb Alloy Interface

Coated on Nb‐C103 substrate through the sol–gel and spark plasma sintering process, MoSi 2 features either a SiO 2 diffusion barrier or SiO 2 ‐10 wt%Yb 2 O 3 barrier. The addition of Yb 2 O 3 significantly enhances the diffusion barrier performance; at 1250 °C, the growth rates of diffusion layers at MoSi 2 /SiO 2 and MoSi 2 /SiO 2 –10Yb 2 O 3 coatings are 0.36 and 0.32 μm 2 h −1 , respectively, significantly lower than the 5.01 μm 2 h −1 rate observed for the coating without a barrier. At 1550 °C, the growth rate of diffusion layer of MoSi 2 /SiO 2 –10Yb 2 O 3 coating is 21.71 μm 2 h −1 , which is only 14% of that of MoSi 2 coating and 44% of that of MoSi 2 /SiO 2 coating. The diffusion barrier layer gradually flows into the holes generated by mutual diffusion and then fails during that specific high‐temperature experiment. The addition of Yb 2 O 3 is found to stabilize the SiO 2 network, increase its viscosity, and effectively retard the diffusion of Si. The life of SiO 2 –10Yb 2 O 3 diffusion barrier is 1.5 times longer than that of SiO 2 diffusion barrier.