Effects of passivating time on the semiconductor properties of passive film formed on an Fe30Mn9Al alloy

Abstract:

The effect of anodic aging time on the constitution, structure and semiconductor properties of passive film formed on an Fe30Mn9Al alloy in 1mol/L Na₂SO₄solution were studied by using combined Auger electron spectroscopy (AES) / X-ray photoelectron spectroscopy (XPS) analysis and the measurement of Mott-Schottky curves. The passive film formed on Fe30Mn9Al alloy in 1mol/L Na₂SO₄solution for 15 min has two layers of inside and outside, and the outside layer has the characteristics of n-type semiconductor, composed of Fe₂O₃, Al₂O₃, Mn₂O₃, FeOOH and AlOOH, the inside layer has the characteristics of p-type semiconductor, composed of MnO. The passive film formed on Fe30Mn9Al alloy in 1mol/L Na₂SO₄solution for 5 h has the characteristics of n-type semiconductor, composed of FeOOH , AlOOH and Mn₂O₃. As the anodic aging time increases from 15 min to 5 h, the Al and Fe contents are enriched and the Mn is depleted, MnO dissolved, the Al and Fe oxides are changed to the Al and Fe hydroxides; The donor densities N_D of the passive film decreased from 2.58′10₂₁ cm_-3 to 1.96′10₂₁ cm_-3, the flat band potential E_fb decreased from -283 mV to -366 mV, respectively.

Key words:Fe30Mn9Al alloy;Passive film; AES/XPS analysis;Mott-Schottky curves;semiconductor properties