Quantum cutting in Tm3+-activated Ca9Gd(PO4)7 phosphors and effect of Tm3+ concentration on emission spectra

Abstract In this work, to develop new quantum cutting (QC) luminescent materials and clarify the QC process, a series of Tm3+-activated Ca9Gd(PO4)7 (CGP) phosphors were prepared by conventional high-temperature solid state reaction method. The phase purity of the samples was checked by XRD patterns, and the structural features were analyzed on the basis of Rietveld refinement. The emission spectra of Tm3+ were measured by exciting at different wavelengths, in which the QC was identified. The main QC model was proposed when the Tm3+ is excited into 1D2 level. The occurrence of QC was further verified by comparing the decay lifetimes on 3H4 level under 357, 470 and 685 nm excitation. With increasing Tm3+ concentration, it was found that the 3H4→3H6 transition intensity around 806 nm exhibits faster increase rate than other ones by exciting at either 357 or 470 nm. This increase rate is more effective under 357 nm excitation thanks to the existence of QC process. The above investigation could show instructional significance for the development of other rare earth ions doped luminescent materials.