Making red-emitting phosphors with Pr3+

UV-excited red-emitting phosphors are obtained using Pr3+ as the luminescent activator and host lattices containing closed-shell transition metal ions (especially titanates, vanadates and niobates). In these oxidant lattices, the quenching of the otherwise greenish- blue emitting 3P0 level is induced by a low-lying Pr-to-metal intervalence charge transfer state (IVCT). A simple criterion based on the optical electronegativities of the d0 lattice cations (Mn+) and average Pr3+ Mn+ distances is proposed to predict 3P0 quenching in these lattices