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.