Distinct Effects of Selective Sn Doping at A or B Sites in BaTiO₃

The effects of selectively doping Sn into the A‐site or B‐site of BaTiO 3 on its crystal structure and electronic and optical properties are systematically evaluated using first‐principles calculations, leading to several intriguing conclusions. After doping Sn at the A‐site, impurity bands originating from Sn are generated, which alter the direct bandgap to an indirect one and decrease the bandgap value, thereby reducing the electron excitation energy required. Meanwhile, (Ba 0.875 Sn 0.125 )TiO 3 (A‐site) exhibits p‐type semiconductor characteristics with holes as carriers, which is beneficial for enhancing the conductivity of BaTiO 3 . The introduction of Sn–O interactions through A‐site Sn doping reduces the density of states of O‐2 p near the valence band maximum, enhances the mobility of oxygen ions, and promotes the occurrence of redox reactions. In contrast, when Sn is doped at the B‐site, the bottom of the conduction band shifts toward higher energy levels, leading to a significant increase in the bandgap. In addition, (Ba 0.875 Sn 0.125 )TiO 3 (A‐site doped) and Ba(Ti 0.875 Sn 0.125 )O 3 (B‐site doped) exhibit distinct optical behaviors, thereby expanding the optical application range of BaTiO 3 ‐based materials. This study highlights the distinct impacts of Sn doping at the A‐site or the B‐site on the modification of BaTiO 3 properties, thereby paving a novel path for designing advanced materials.