Oxidation of φ′-aluminium oxynitride

► Oxidation of φ′-AlON has been studied for the first time. ► First corrosion products are γ-alumina. ► Low density α-alumina is formed at high temperature. ► Grains are extensively cracked after oxidation. ► The low density of the α-alumina is due to a network of nanometric porosities.