Emission properties of (SrTiO3-TiO2):Pr 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.