Pr and Al doping effects on the red emission and long lasting afterglow in CaTiO3 single crystals

In this study, how the concentration of added ions and excitation energy play a role in the red afterglow in CaTiO3:Pr, Al was investigated from photoluminescence, photoluminescence excitation and thermoluminescence spectra of single-crystal samples with different concentrations. The analysis shows that the traps that provide afterglow are mainly caused by Ca defects induced by the addition of Pr, and that the energy positions of these trap levels are optimized by lattice relaxation when Al is co-doped in moderate amounts for charge compensation, resulting in the longest afterglow. Additions of Aland Pr in excess of the optimum amount increase the number of deep levels due to oxygen defects and shallow trap levels due to Ca defects, respectively, and inhibit electron accumulation in the afterglow trap. Through systematic measurements and analysis, we have shown that it is possible to separate the contribution of luminescent ions and co-doped ions to the afterglow, and we have proposed a coordination coordinate diagram that allows a unified interpretation of the results. These are essential elements for the development strategy and evaluation of phosphors exhibiting long afterglow.