Impedance spectroscopy study of high-temperature oxidation of Gd ₂O₃-Yb₂O₃ codoped zirconia thermal barrier coatings

3Gd₂O₃-3Yb₂O₃-4Y ₂O₃ (mole fraction, ) co-doped ZrO₂ (GY-YSZ) thermal barrier coatings (TBCs) were produced by electron beam physical vapor deposition (EB-PVD). The oxidation behavior of GY-YSZ at 1 050 °C was investigated using impedance spectroscopy (IS) combined with scanning electron microscopy (SEM), Raman spectroscopy and X-ray diffractometry (XRD). Various electrical responses observed in the impedance spectra corresponding to GY-YSZ grains and grain boundaries were explained using circuit modeling. The change in the conduction mechanism of GY-YSZ was found to be related to the O ^2- vacancy and lattice distortion due to the stabilizer diffusion during the oxidation. The results also suggested that the specific oxidation information about the GY-YSZ grains and grain boundaries should be acquired at a moderate measurement temperature, which was related to the resistance value in the impedance spectra. The resistance values of the GY-YSZ grains and grain boundaries should be measured at 200 °C and 300 °C, respectively.