Initial corrosion mechanism of Hf6Ta2O17 ceramic for TBCs against CMAS infiltration: Experiment and first-principle simulation

The initial calcium–magnesium–alumino–silicate (CMAS) corrosion mechanism of Hf ₆Ta ₂O ₁₇ ceramic at 1250 °C for TBC was investigated by experiment and first–principle simulation. The results showed that the Hf atom, originating from Hf ₆Ta ₂O ₁₇ , substituted the Si atom of the CMAS structure, increasing the melting point of the CMAS by changing its elastic constant, which tended to prevent further penetrating of the CMAS. Meanwhile, the Ca atom, stemming from CMAS, diffused into the Hf ₆Ta ₂O ₁₇ structure and occupied the interstitial site, increasing the optical basicity value of the Hf ₆Ta ₂O ₁₇ , which was advantageous to develop a dense corrosion product layer to block the CMAS corrosion attack.