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, MoSi₂ features either a SiO₂ diffusion barrier or SiO₂‐10 wt%Yb₂O₃ barrier. The addition of Yb₂O₃ significantly enhances the diffusion barrier performance; at 1250 °C, the growth rates of diffusion layers at MoSi₂/SiO₂ and MoSi₂/SiO₂–10Yb₂O₃ coatings are 0.36 and 0.32 μm² h⁻¹, respectively, significantly lower than the 5.01 μm² h⁻¹ rate observed for the coating without a barrier. At 1550 °C, the growth rate of diffusion layer of MoSi₂/SiO₂–10Yb₂O₃ coating is 21.71 μm² h⁻¹, which is only 14% of that of MoSi₂ coating and 44% of that of MoSi₂/SiO₂ 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 Yb₂O₃ is found to stabilize the SiO₂ network, increase its viscosity, and effectively retard the diffusion of Si. The life of SiO₂–10Yb₂O₃ diffusion barrier is 1.5 times longer than that of SiO₂ diffusion barrier.