Hot corrosion evaluation of Gd2O3-Yb2O3 co-doped Y2O3 stabilized ZrO2 thermal barrier oxides exposed to Na2SO4+V2O5 molten salt

1 mol% Gd2O3 and 1 mol% Yb2O3 co-doped 3.5 mol% Y2O3 stabilized ZrO2 (GdYb-YSZ) ceramics in metastable tetragonal (t') structure were fabricated, and their hot corrosion behaviors were evaluated. The corrosion tests were performed at 700 degrees C, 800 degrees C, 900 degrees C and 1000 degrees C for 4 h in the presence of Na2SO4+V2O5 molten salt. After corrosion, t' phase could still be detected on the corroded surfaces and its content decreased with increasing the corrosion temperature. The corrosion products were composed of doped YVO4 and m-ZrO2, but some amounts of Na4V2O7 were found at low corrosion temperatures (700 degrees C and 800 degrees C). The corrosion resistance characteristic of GdYb-YSZ was compared with that of YSZ. Under an identical corrosion condition, GdYb-YSZ had less monoclinic phase formed, indicative of a better hot corrosion resistance. The hot corrosion mechanism was discussed in detail.