Ion—Ion Interactions in Rare-Earth-Doped LaF3

Abstract

A systematic study of quantum efficiencies and lifetimes has been carried out for the visible fluorescences of Pr3+ in single-crystal LaF3. An analysis of the results as a function of Pr3+ concentration is given in terms of a two-site model in which a Pr3+ ion can either be in an isolated site or in a site where it is coupled to other impurity ions. This model leads to ion—ion interaction ranges varying from ∼5 Å (nearest neighbor) to ∼12 Å depending on the fluorescent level studied. Throughout this range of interaction lengths, Dexter's model of electrostatic ion—ion interaction shows that the dominant contribution comes from the quadrupole—quadrupole term. Temperature effects in the interaction are consistent with the lack of exact resonance between the electronic levels. It appears that the lattice can readily absorb excess energy up to ∼1000 cm−1. A set of samples doped with a second rare earth (Ce3+, Nd3+, Eu3+, Gd3+, Tb3+, Dy3+, Ho3+, Er3+, Tm3+, Yb3+) has demonstrated the existence of selection rules for ion—ion interaction in addition to energy-matching requirements. The system 0.5% Pr3+: x% Ce3+ has been studied in more detail.

Dynamics of the excitation and upconversion processes in YAlO3: Pr single crystals

“…As we know, the signature of such processes is generally a deviation of the decay pattern from a pure exponential behavior. Specifically, there was no evidence of the cross-relaxation process that leads to concentration quenching of the 3 P 0 level, as there is in other host materials [18,19]. The reason for this is probably due to the lack of resonance in the cross-relaxation process: 3 P 0 + 3 H 4 -1 G 4 + 1 G 4 .…”

“…This behavior is likely due to a crossrelaxation process that leads to quenching of luminescence from the 1 D 2 level. As reported by others [18][19][20], the likely path of this cross-relaxation path is: 1 D 2 + 3 H 4 -1 G 4 + 3 F 3 . We note that as the temperature is increased, the lifetime becomes shorter, the nonexponential component of the decay curve becomes more prominent, and the emission intensity decreases with the lifetime (Fig.…”

“…From 1 D 2 there are several mechanisms through which the system is known to decay: radiative, cross-relaxation between Pr ions, multiphonon decay, and upconversion. The cross-relaxation process is known to seriously quench the 1 D 2 luminescence in some systems [18][19][20][21]. This quenching can be deleterious for the upconversion process as well, since it depletes the population of the 1 D 2 level.…”

Dynamical processes of Ln3+ ions doped in LaF3 nanocrystals embedded in transparent oxyfluoride glass

“…Taking the values of W 1 and W 3 from Ref. [26] and using Eq. (6) to fit the buildup of the curves plotted in Fig.…”

A brief review of co-doping

“…For example, these words were used to describe interactions between Eu 3+ and other rare earth elements in Y 2 O 3 [34], the effect of Pr 3+ fluorescence on LaF 3 owing to the presence of other rare earth co-dopants [35], the characteristics of Nd…”