Enhancement of characteristic red emission from SrTiO3:Pr3+ by Al addition

The mechanism of enhancement on the red emission efficiency from SrTiO3:Pr3+ (D-1(2)-->H-3(4) emission of Pr3+) by Al addition has been investigated. The emission intensity at room temperature for the phosphor, SrTiO3:Pr3+ synthesized with 23 mol % Al is about 200 times higher than Al-free samples. Photoluminescence (PL) spectra at low temperatures show the progress of several red emission lines of the D-1(2)-->H-3(4) transition with an increase in Al molar ratio. The lines are probably due to formation of Al-associated Pr3+ centers. The Al-associated Pr3+ PL does not exhibit thermal quenching up to room temperature. Temperature dependent PL spectra below 100 K and PL excitation spectra reveal that the energy transfer occurs from photoexcited carriers in SrTiO3 host to PL centers. The PL intensity, x-ray diffraction measurements, and high-resolution transmission electron microscope images indicate the improvement of crystallinity of SrTiO3:Pr3+ with Al addition, resulting in a decrease in defects and probably an increase in the energy transfer to radiative centers. These observations imply that both the increase of the Al-associated Pr3+ luminescence centers and the improvement of the crystallinity result in the enhancement of the D-1(2)-->H-3(4) emission. (C) 1999 American Institute of Physics. [S0021-8979(99)02822-4].