The red phosphor CaTiO3 : Pr3+ is known to show a persistent luminescence in the red spectral region upon irradiation in the UV. Although a number of studies have been dedicated to the enhancement of the afterglow efficiency in this perovskite by varying the preparation method, the chemical composition or the particle size, no clear explanation of the mechanisms involved in the afterglow process has been given yet. The purpose of this paper is to start investigating this aspect on the basis of a recently developed model and by using the luminescence and afterglow properties of the solid solution (Ca, Sr)TiO3 : Pr3+ as experimental support.

The Pr(3+)-doped NaNbO(3) perovskite is introduced as a new red phosphor excitable in the near UV region at around 350 nm. A bright single red emission is observed at room temperature and ascribed to transitions between the (1)D(2) excited state and the ground state (3)H(4) of Pr(3+) ions. This peculiar behavior is related to the presence of a low-lying intervalence charge transfer state that contributes to quench the emission from the otherwise emitting (3)P(0) level. Red afterglow is also evidenced in NaNbO(3):Pr(3+). A preliminary model is discussed to clarify the afterglow mechanism.