The enhancement, by Al additions, of the efficiency of red emissions (1D2 → 3H4 of Pr3+) from Pr3+-doped material was investigated. The room-temperature emission intensity of a Pr3+-doped phosphor which contained 23mol%Al was about 200 times greater than that of Al-free samples. Low-temperature photoluminescence spectra revealed the progress of several red emission lines with increases in Al molar ratio. The lines were thought to be due to the formation of Al-associated Pr3+ centers. The latter did not exhibit thermal quenching at up to room temperature. Temperature-dependent photoluminescence spectra below 100K, and photoluminescence excitation spectra, revealed that energy transfer occurred from photo-excited carriers in the host, to photoluminescence centers. Photoluminescence intensity, X-ray diffraction data and high-resolution transmission electron microscopic images indicated an improvement in the crystallinity of Pr3+-doped material with Al additions. This resulted in a decrease in the number of defects and probably to an increase in the energy transfer to radiative centers. It was concluded that the increase in Al-associated Pr3+ luminescence centers and the improvement in crystallinity both resulted in an enhancement of the 1D2 → 3H4 emission.

Enhancement of Characteristic Red Emission from SrTiO3:Pr3+ by Al Addition. S.Okamoto, H.Kobayashi, H.Yamamoto: Journal of Applied Physics, 1999, 86[10], 5594-7