Emission properties of (SrTiO3–TiO2):Pr3+ eutectic with self-organized fractal microstructure

An investigation of spectroscopic properties of (SrTiO3–TiO2):Pr3+ eutectic and, for comparison, of bulk SrTiO3:Pr3+ and TiO2:Pr3+crystals is presented. Luminescence spectra have been measured under both 450 nm and 350 nm excitation wavelength. For UV excitation they are characterized by a dominant red luminescence corresponding to transition from the 1D2 level of Pr3+ ions. The mechanism responsible for quenching of blue (from 3P0 state) and intensification of red luminescence is proposed to be thermally-induced radiationless relaxation involving a low-lying Pr3+–Ti4+ intervalence charge transfer state. Measured decay constants of 1D2 excited state of Pr3+ are compared with values obtained for other praseodymium doped titanate hosts.

► Luminescence induced after UV excitation is dominated by the 1D2–3H4 transition.
► Intervalence charge transfer exhibits thermally-depended character.
► Decay constants of Pr3+ in SrTiO3–TiO2 are shorter than in SrTiO3 bulk crystal.