Thermal stability of nanostructured 13 wt% Al2O3–8 wt% Y2O3–ZrO2 thermal barrier coatings

Nanostructured 13 wt% Al2O3–8 wt% Y2O3–ZrO2 (13AlYSZ) coatings were developed by atmospheric plasma spraying (APS). The phase structure and the morphology of the 13AlYSZ coatings were characterized using X-ray diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscope (TEM). It was found that the as-sprayed coatings mainly consisted of tetragonal zirconia, with the Al element solid solution in ZrO2. Heat treatment at 1100 °C increased the average grain size of the ZrO2 phase from 61 to 120 nm and decreased the porosity from 23.8 to 18%. The addition of the nano-Al2O3 can effectively inhibit the grain growth of the zirconia phase. The mechanism on inhibiting the grain growth of nanostructured 8 wt% Y2O3–ZrO2 thermal barrier coatings has been discussed in detail.