Effect of Al2O3 modification on the properties of YSZ: Corrosion resistant, wetting and thermal-mechanical properties

Calcium-magnesium-alumino-silicate (CMAS) corrosion is one of the main failure modes of thermal barrier coatings (TBCs). Al2O3-modified YSZ (Y2O3-stabilised ZrO2) coatings can resist it. Here, the effect of the Al2O3 content in YSZ on the resistance of CMAS corrosion was investigated by means of differential scanning calorimetry (DSC), X-ray diffraction (XRD) and wetting tests. The thermal properties of samples, the Young's modulus and fracture toughness of Al2O3-modified YSZ were studied by thermal conductivity and Vickers hardness test, respectively. The results demonstrate that when the Al2O3 content is 40 mol%, the Al2O3-modified YSZ has the best properties to resist CMAS corrosion due to the formation of anorthite which has a high melt point. Furthermore, the phase diagram and phases mole fractions with different Al2O3 content were calculated which match well with the experiments. With the increase of Al2O3 modification content, the thermal conductivity, Young's modulus and fracture toughness of the sample increase.