THERMALLY-INDUCED TRANSFORMATIONS AT AN ION-IMPLANTED ALPHA-FE2O3 ALPHA-AL2O3 INTERFACE - A MOSSBAUER-SPECTROSCOPY STUDY/

Thermally induced chemical transformations at the interface between a 100 nm alpha-Fe2O3 and a polycrystalline alpha-Al2O3 substrate are stu died and compared for the cases of the as-formed and ion bombarded int erfaces. The thermal annealings are carried out under vacuum at 450 de grees C for different time durations and the transformations are exami ned by conversion electron Mossbauer spectroscopy. It is shown that in the sample prebombarded with 110 keV Ar+ ions, the formation of Fe3-x AlxO4, FeAl2O4, and FeO phases is favored at variance with a nonbombar ded sample in which primarily a defective Fe3O4-y phase is produced wi th some amount of FeO. This difference is explained in terms of the an nealing process of the oxygen vacancies produced during Ar implantatio n near the interfacial region. (C) 1996 American Institute of Physics.