This assumption allows to explain the Ti segregation toward the surface leading to Ti-rich phase upon annealing. Indeed, when increasing the temperature, the Cl bonded with Ti will easily migrate toward the surface of the hematite resulting in Ti surface segregation. Such segregation was reported equally for Tidoped hematite obtained by different synthesis methods, but in the absence of adapted spectromicroscopy techniques, it was supposed that the Ti-rich phase is TiO2. In our case the Ti-rich phase present Ti-O6 coordination, but different in terms of interatomic distances and angles of the octahedra from those constituting the Ti-doped hematite structure (assimilated to an ilmenite structure). This idea is supported by the Ti L2,3 absorption spectral features (i.e. shift toward higher energies of the Ti L3 t2g and asymmetry of the Ti L3 eg peak). Indeed, the Fe2TiO5 can be expressed as a phase aggregation: 𝐹𝑒 2 𝑇𝑖𝑂 5 = 𝐹𝑒 2 𝑂 3 + 𝑇𝑖𝑂 2 . Interestingly, this aggregation occurs only when annealing under Nitrogen, the air annealing producing only a Ti substitution gradient without pseudo-brookite phase formation in that case. Most probably the presence of Oxygen stabilizes a homogeneous phase at the surface of the Ti-doped hematite that can be assimilated to ilmenite, while Nitrogen promotes phase separation between Ti-doped hematite (𝐹𝑒 2-𝑥 𝑇𝑖 𝑥 𝑂 3 , 𝑤𝑖𝑡ℎ 𝑥 ≤ 1) and pseudo-brookite.