Thermal Release Behavior of Carriers in Persistent Luminescence Material CaAl₂O₄:Eu²⁺,Nd³⁺

Abstract

To reveal the detailed migration processes of carriers thermally released from defects in CaAl2O4:Eu2+,Nd3+, their thermoluminescence curves recorded at different fading time were investigated. The results indicated that their trapping levels and kinetic orders were varying with fading time. As the persistent luminescence properties of CaAl2O4:Eu2+,Nd3+ are closely related with the migration manners of carriers, the variety of kinetic order indicated that the mechanism(s) of persistent luminescence is(are) more complicated than we previous proposed. Furthermore, the details of carrier thermal release processes and carrier transfer processes are illustrated with the aid of variety of parameters derived from TL curves.

Mechanistic Study of the Persistent Luminescence of CaAl2O4:Eu,Nd

“…On the other hand, the empty Nd 4f levels can serve as electron traps to prolong the luminescence time. Our calculations are in good agreement with the experimental result that shows that the traps are distributed over a wide energy range of 0.5–1.2 eV. ,, Note that the depths of the Nd 4f levels are deeper than those of V O 2+ , so trapped electrons in Nd 4f levels are more difficult to release than those trapped in the impurity levels of V O 2+ . As such, the luminescence time should be prolonged significantly because of the doping of Nd.…”

“…Regardless of the type of carrier trap center, the PL mechanism is believed to be closely related to the electronic properties of the luminescent center Eu and intrinsic/extrinsic defects acting as trap centers. ,, Hence, it is important to gain deeper insights into the electronic properties of the dopants and defects, especially when they are at high concentrations. ,, For the luminescent center Eu, the 4f levels are located in the band gap while 5d levels are probably at the bottom of the conduction band . With respect to the intrinsic defects, because the reducing annealing conditions and high annealing temperatures may generate both O and Ca vacancies (V O and V Ca , respectively) in CaAl 2 O 4 :Eu, the roles of these defects are expected to be crucial to the PL phenomena.…”

How to induce highly efficient long-lasting phosphorescence in a lamp with a commercial phosphor: a facile method and fundamental mechanisms

“…46,49,50 To examine the trap depth and the LLP kinetics of the Zn 2 SiO 4 :Mn 2+ ,Yb 3+ , we introduced a classical multi-peak fitting method developed by Chen et al 51 Considering that the retrapping effect cannot neglected in this case, the general-order kinetics expression should be utilized to describe the TL glow curves:…”