Effect of Al addition on the yellowness of V-doped t-ZrO₂: A first-principles study

Abstract

First-principles calculations were performed to clarify the reason for the increase in yellowness upon the addition of Al to V-doped tetragonal ZrO₂ (t-ZrO₂). First-principles energy band calculations were performed using V-doped and (V, Al)-doped t-ZrO₂ supercells with theoretically optimized structures. When t-ZrO₂ was doped with V, the band gap exhibited a strongly localized energy level originating from the V 3d states. The V-doped t-ZrO₂ supercell co-doped with Al modified the number and energy positions of the V 3d levels within the ZrO₂ band gap. In the calculated dielectric function of the V-doped ZrO₂ supercell, broad absorption from the O 2p VB states to the V 3d gap states was observed in the visible region, in addition to the d-d transition in V⁴⁺. When Al was co-doped in the V-doped t-ZrO₂, no increase in the optical absorption in the visible-light region was observed. In contrast, the (V, Al)-doped t-ZrO₂ supercells with oxygen vacancies exhibited stronger absorption in the visible light region than the V-doped t-ZrO₂ supercell.