Mössbauer Effect for Fe57 in Al2O3—Effects of Variety of Heat Treatments

Abstract

The reduction of the ${\mathrm{Al}}_2$ ${\mathrm{O}}_3$: ${\mathrm{Fe}}^{57}$ system in a hydrogen atmosphere causes the formation of metallic iron clusters yielding hyperfine-split spectra. On firing in air, these clusters are first converted to ${\mathrm{Fe}}_2$ ${\mathrm{O}}_3$, which subsequently dissolves in the lattice to give ${\mathrm{Fe}}^{3+}$ at the ${\mathrm{Al}}^{3+}$ site. Vacuum firing, however, merely tends to stabilize the ${\mathrm{Fe}}^{2+}$ state in addition to the normal ${\mathrm{Fe}}^{3+}$ state.