2022 年 130 巻 12 号 p. 925-932
A first-principles energy band calculation was performed for V-doped ZrO2, (M,V)-doped ZrO2 (M = Al, Y, La) supercells, and pure ZrO2 unit cells to elucidate the effects of M doping on the electronic structure and optical properties of a V-doped ZrO2 pigment. Structural optimization calculations revealed that the calculated lattice constants of ZrO2 agreed well with those obtained from experimental data. Using a generalized gradient approximation calculation, the minimum bandgap was estimated to be 3.67 eV. Density of states calculations indicated that the valence band (VB) was mainly composed of O 2p states mixed with Zr 4d states. The conduction band (CB) was mainly composed of Zr 4d states with small O 2p character. For V-doped ZrO2, three minority-spin and four majority-spin localized states newly appeared in the bulk ZrO2 bandgap. They were mainly derived from V 3d states. The addition of a second element, M, to V-doped ZrO2 changed the energy position and peak number of the localized V 3d states in the bandgap. This change was most pronounced for La, which has the largest ionic radius of all M. Based on the dielectric function calculation of the V-doped ZrO2 supercell, there was a broad absorption from the O 2p VB states to the V 3d gap states occurring from the ligand–metal charge transfer (LMCT) and dd transition of V4+ ions, as well as a VB–CB optical transition in the ZrO2 bulk. Furthermore, when an M atom was added to the V-doped ZrO2 supercell, the optical absorption by the LMCT was considerably enhanced in the visible region. Based on these calculations, which supplement the research on common inorganic dyes, we conclude that the addition of a second element, M, is effective in enhancing the chromogenicity of the Zr-yellow pigment.
