Photoluminescence Piezospectroscopy Research Articles

Stress-Driven Wrinkling oF α-Alumina Films Grown oN Fe-Cr-Al by Thermal Oxidation

AbstractA thin α-Al2O3 film forms on Fe-20w/oCr-5w/oAl alloys when they are heated in air to about 1000°C. This thermally grown oxide exhibits a wrinkled morphology within minutes and with an amplitude and characteristic wavelength that increases with oxidation time. Measurements of the residual strain in the oxide, using Cr3+ photoluminescence piezospectroscopy, indicate that the wrinkling is associated with stress relaxation during the course of the thickening of the oxide. AFM and piezospectroscopic measurements reveal a strong time dependence of the growth stress and oxide wrinkling, as well as a marked dependence on the crystallographic orientation of the underlying Fe-Cr-Al substrate. Small additions (about 0.3 w/o) of yttrium to the metal completely suppress the wrinkling phenomenon although it is found not to lessen the growth stresses in the oxide film.