Fe-Al-O layers were prepared at different temperatures (between 20 degrees C and 600 degrees C) by ion implantation and ion-beam sputtering. By the use of conversion electron Mossbauer spectroscopy it was possible to observe the charge states of iron atoms and then to determine the effect of the temperature on the compound formation. In the two fabrication processes small iron particles and FeAl2O4 are produced. However, at 20 degrees C some differences are observed in the chemical state : Fe(IV) and alpha-Fe are detected in implanted layers only. From 400 degrees C the main effect of temperature is to favour the formation of dispersed iron particles in alumina with bigger precipitates for ion-implanted samples.