The direct identification of quantum cutting in Tm3+ ions and energy transfer in the Tm3+/Yb3+ system based on a Ba2Gd2Si4O13 oxide host

Abstract

Quantum cutting (QC) is an important physical process, the occurrence of which still needs further verification in different luminescent ions. In this work, a series of Tm³⁺/Yb³⁺ doped Ba₂Gd₂Si₄O₁₃ (BGS) phosphors were prepared by a solid-state reaction method. The phase purity, crystal structure, morphology, luminescence properties and QC characteristics were studied. In the BGS:Tm³⁺ samples, the QC phenomenon was directly observed and verified upon 355 and 472 nm excitation. The cross-relaxation processes and QC models were analyzed, and then proposed according to the spectral features. A method for the calculation of extra quantum efficiency was developed on the basis of the emission spectra. In the Tm³⁺–Yb³⁺ codoped BGS phosphors, the energy transfer (ET) from different excited states of Tm³⁺ to Yb³⁺ takes place via different ways. The contributions of different excited levels of Tm³⁺ to Yb³⁺ luminescence were evaluated by a defined relative ET efficiency ratio (R_η), which revealed that the contribution of the ¹D₂ level is much larger than those of other excited states of Tm³⁺.