Improvement of red-emitting afterglow properties via tuning electronic structure in perovskite-type (Ca1-xNax) [Ti1-xNbx] O3: Pr3+ compounds

The red persistent luminescence of CaTiO3:Pr3+ needs further improvement in longer excitation wavelength to fulfill the application demand. By Na+-Nb5+ substituting for Ca2+-Ti4+, a series of Pr3+-doped perovskite-type (Ca1-xNax) [Ti1-xNbx]O3:0.001Pr3+ compounds, with a structural transition at about x = 0.7-0.8, have been successfully synthesized by a solid state reaction. The excitation band first red-shift and then blue-shift gradually with x. The afterglow duration has been prolonged from 30 s for CaTiO3:Pr3+ to about 60 s for the composition x = 0.1. Wavelength-dependent trap filling analysis show that the charging wavelengths can be red-shifted from UV irradiation (<358 nm) for CaTiO3:Pr3+ to visible violet light for compositions with x = 0.1. On the basis of spectral data, we construct the host referred binding energy (HRBE) and vacuum referred binding energy (VRBE) schemes of trivalent lanthanide-doped (Ca1-xNax) [Ti1-xNbx] O3 compounds, and further explain these afterglow behaviors. This work is helpful for exploring novel persistent luminescent materials.