First-principles study of structure,mechanical and optical properties of La-and Sc-doped Y_2O_3

The electronic, mechanical and optical properties of La-and Sc-doped Y₂O₃ were investigated using first-principles calculations. Two doping sites of Sc and La in Y₂O₃ were modeled. The calculated values of the energy of formation show that the most energetically favorable site for a La atom in Y₂O₃ is a d-site Y atom, while for Sc a b-site Y atom is the more stable position. The calculated band gap shows a slight decrease with increasing La or Sc concentration. The calculated results for the mechanical and optical properties of Y_2–xR_xO₃ (R = Sc or La, 0 < x ≤ 0.1875) show that La- or Sc-doped Y₂O₃ would have enhanced strength, and thus an ability of resisting external shocks, and increased hardness and mechanical toughness. These improved mechanical properties are achieved without sacrificing the optical properties of the doped compounds. So the doping of La or Sc in Y₂O₃ is permissible in the preparation of Y₂O₃ transparent ceramics, of course, doping of La or Sc will benefit the sintering of transparent ceramics.