Thermophysical Properties and CMAS Corrosion Resistance of Sc₂O₃-Modified YSZ Ceramics

The 6% （molar fraction, the same below） Sc₂O₃-modified 2%Y₂O₃-ZrO₂ ceramics （SYSZ ceramics） was prepared by solid-phase synthesis method. The high-temperature phase stability at 1 400 ℃ and thermophysical properties of SYSZ ceramics, as well as the CMAS （mass ratio of CaO, MgO, Al₂O₃, SiO₂ and Fe₂O₃ of 21∶7∶19∶42∶11） corrosion resistance at 1 250 ℃ were investigated and compared with those of 8wt%Y₂O₃-ZrO₂ ceramics （YSZ ceramics）. The results show that before and after heat treatment at 1 400 ℃ for 500 h, SYSZ ceramics all had a t-tetravalent phase structure, and no obvious m monoclonal phase appeared. However, the m phase existed in YSZ ceramics. The doping of Sc₂O₃ could effectively improve the high-temperature phase stability of YSZ ceramics. The thermal conductivity of SYSZ ceramics first decreased with the increase of temperature, reached the minimum value near 600 ℃, and then increased slowly. The thermal conductivity at different temperatures of SYSZ ceramics was significantly lower than that of YSZ ceramics. The thermal conductivity at 1 200 ℃ was 1.79 W·m⁻¹·K⁻¹, which was approximately 16% lower than that of YSZ ceramics. With the increase of temperature, the coefficient of thermal expansion of SYSZ ceramics showed an approximately linear increasing trend, slightly lower than that of YSZ ceramics. After being corroded in CMAS at 1 250 ℃ for 10 h, the surface of SYSZ ceramics presented a rod-like structure with a tight arrangement. Compared with those of YSZ ceramics, the thickness of the reaction layer formed on the surface of SYSZ ceramics was reduced by 85%, and the content of m phase in the reaction layer was significantly lower under the same condition. SYSZ ceramics showed better CMAS corrosion resistance.