Effects of Zn impurities on the electronic properties of Pr doped CaTiO3

Microcosmic investigations of weak red-emitting materials are crucial for their further development and application. In this work, we have focused on the band structures and electronic properties of Pr mono- and (Zn, Pr) co-doped CaTiO3 using density functional theory. Zn substitution for Ca or Ti tends to form clusters energetically with Pr substituting for Ca in CaTiO3. In Pr mono-doped CaTiO3, the O2p→Ti3d transition in CaTiO3 host corresponds to the centered 330 nm excitation spectra. The gap states above the valence band of ∼1.30 eV and ∼2.06 eV are hybridized by Pr4f, O2p and Ti3d orbitals. They are mainly due to Pr4f orbitals in CaTiO3:Pr. The former gap level is related to red emission at 614 nm due to 1D2→3H4 transition of Pr3+ activator. The latter is related to the excitation spectra centered at 380 nm due to the low-lying Pr-to-mental intervalence charge transfer transitions (Pr3+-O2−-Ti4+⇌Pr4+-O2−-Ti3+). The band structures of (Zn, Pr) co-doped CaTiO3 keep the similar gap levels to those in Pr mono-doped CaTiO3. The incorporation of Zn brings out the two stronger localized gap states, which are hybridized by Pr4f, O2p and Ti3d orbitals, in comparison with those in Pr mono-doped CaTiO3. Therefore, when Zn impurities are added into Pr doped CaTiO3, the present calculations visualize the two enhanced levels and the distorted structures around Pr.