Temperature Dependence of Rate Constants for Tb³⁺(⁵D₃) Cross Relaxation in Symmetric Tb³⁺ Pairs in Tb-Doped CsCdBr₃, CsMgBr₃, CsMgCl₃

Abstract

Microscopic rate constants for Tb(5D3) cross relaxation have been determined as a function of temperature in symmetrical Tb3+−Tb3+ pairs in CsCdBr3, CsMgBr3 and CsMgCl3. The temperature dependence and maximum efficiency of cross relaxation is very different in the three hosts, despite the fact that the energy-level structures and luminescence spectra are quite similar. The difference in cross relaxation behavior in the three systems is due to the fact that the degree of resonance is the dominant factor in determining transfer efficiencies, easily outweighing the influences of general transition strengths and donor−acceptor separations. Only donor and acceptor transitions with significant overlap of the zero-phonon spectral lines participate in active transfer mechanisms. The temperature dependence of cross relaxation is due to the changing thermal populations of the initial crystal-field levels of resonant donor and acceptor transitions. All transitions in resonance involve a “hot” crystal-field transition, either on the donor, on the acceptor, or on both. The marked differences in the temperature dependence of cross relaxation in the three systems are attributed to slight differences in crystal-field energy-level structures, which, in turn, result in different crystal-field transitions being in resonance in the three systems. Although phonon-assisted processes are not discounted, they do not appear to have a significant impact on the temperature dependence of cross relaxation. Crystal-field analyses for Tb3+ in symmetric pairs in the three hosts are also reported.

Investigation on charging processes and phosphorescent efficiency of SrAl2O4:Eu,Dy

“…(5) is actually a cross relaxation between the à Eu 2þ and ½Eu 2þ þ à e centers. Cross relaxation takes place via the pairs of the energy donors and acceptors existing in the crystal lattices [7] or the energy migration among the donors [8,9]. The latter is believed to be the case because of the overlap between the excitation and emission spectra of Eu 2+ in SrAl 2 O 4 , as shown in Fig.…”

Interionic cross relaxation and tunable color luminescence in KY3F10:Tb3+ nano/microcrystals synthesized by hydrothermal approach

“…Therefore, Tb 3+ activated phosphors with tunable emitting colors can be achieved by choosing a low phonon frequency host. We summarize the reported tunable color luminescence in Tb 3+ doped materials [25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41], as shown in Table 1. The approximate values of the phonon frequency in some oxides containing ionic complexes and fluoride compounds have been reported, such as borates ($1300 cm À1 ), phosphates ($1200 cm À1 ), silicates ($1050 cm À1 ), tungstates ($900 cm À1 ), aluminates ($850 cm À1 ), fluorides ($450 cm À1 ).…”

“…Fig. 3 shows the PL spectra of KY 3 F 10 :Tb 3+ with different Tb 3+ concentrations under 218 nm excitation, where the intensities of the blue Halide compounds Ca 6 Ln 2 Na 2 (PO 4 ) 6 F 2 (Ln = Gd, La) [34] Rb 2 KInF 6 [35] b-NaYF 4 [36] K 2 YF 5 [37] ZBLAN [38] a-GdOF [39] CsMgCl 3 [40] CsMgBr 3 [40] CsCdBr 3 [40,41] emission originating from 5 D 3 are normalized. At low concentrations of Tb 3+ , the blue emissions from the 5 D 3 level are dominant in the fluorescence spectra, indicating that the 5 D 3 level is effectively populated when excited at 4f 7 5d configuration.…”

5D3–5D4 cross-relaxation of Tb3+ in a cubic host lattice

“…The energy transfer mechanism was deduced to be electric dipole-electric dipole (ED-ED) for Y 3 Al 5 O 12 :Tb 3+ [12], a-GdOF [13] and for LiYF 4 :Tb 3+ above 70 K [10], but electric quadrupole-electric quadrupole (EQ-EQ) at 4.2 K for LiYF 4 :Tb 3+ . From a detailed consideration of the crystal field energy levels for the systems CsCdBr 3 , CsMgBr 3 and CsMgCl 3 doped with Tb 3+ at a C 3v site [14], it was concluded that the cross-relaxation mechanism involved resonant 'hot' transitions and that phonon-assisted processes were not important. As mentioned above, since dipole-dipole processes are forbidden for Cs 2 NaYF 6 :Tb 3+ unless they are phonon-assisted, it was of interest to investigate the 5 D 3 concentration quenching in this system in view of the above conclusions.…”