Fig. 1. GIXRD patterns of samples obtained at different oxidation vacuum (a) 120 Pa, (b) 1.2 Pa

Fig. 2. Surface morphologies of samples heated at 750~850 ℃ for 72 h under 120 Pa or 1.2 Pa

Fig. 3. Surface morphologies of samples formed at 1.2 Pa-900 ℃-72 h

Fig. 4. Cross-sectional SEM images of coating obtained at 1.2 Pa-850 ℃-72 h, the whole coating (a) and the element depth distribution corresponding to (b). The enlarged area in (a) (c) and element depth distribution corresponding to (d)

Fig. 5. The corresponding selected area electron diffraction (SAED) pattern of Al₂O₃ film obtained at 1.2 Pa-850 ℃-72 h