“…This is caused by the capacity of the lanthanide ions to form complexes of different Lewis bases (for example, acids, amines, aldehydes, alcohols, thiols) because of the interaction of these functional groups with the f orbitals of lanthanides [52e54]. The XRD pattern of TiO 2 :Sm 3þ is similar to TiO 2 by not showing additional diffraction peaks, suggesting that the Sm 3þ ions are incorporated within the crystal lattice of TiO 2 [33,55]. In the case of the substitutional solid solution, the dopant ions can enter the anatase crystal lattice and influence the level of oxygen vacancies (annihilating), also leading to the formation of Ti interstitial and thus inhibit the transformation.…”