Microstructure of iron implanted Al2O3 and Zr2 ceramics

This paper reports on Al2O3 and ZrO2 ceramics implanted with 57Fe+ ions and then annealed under various atmospheres (O2,H2,Ar). Conversion electron Mossbauer spectroscopy, transmission electron microscopy and Rutherford backscattering techniques were used to characterize implanted layers of as-implanted and annealed samples. After implantation iron was distributed among different charge states with the relative amount of each varying with concentration of implanted iron. Annealing under oxygen or hydrogen atmospheres of sapphire lead to different thermal evolutions for local environment of the implanted iron. The oxidation process of iron during annealing under oxygen of a sintered Al2O3 sample is carefully followed. After formation of large α-Fe2O3 precipitates around 1200 degrees C there is a complete disappearance of this phase at 1 400 degrees C. For ZrO2 the oxidation of iron is very fast and complete around 400 degrees C. In all samples (sapphire, sintered alumina, zirconia foils) some iron atoms remain substitionnally substituted even at very high temperatures