Thermally Stimulated Luminescence and First-Principle Study of Defect Configurations in the Perovskite-Type Hydrides LiMH₃:Eu²⁺ (M = Sr, Ba) and the Corresponding Deuterides

Abstract

Temperature-dependent photoluminescence (PL) as well as thermoluminescence (TL) were studied in the Eu2+-doped hydrides LiMH3 (M = Sr, Ba) and the corresponding deuterides. Here, thermally stimulated luminescence was observed for the first time in a Eu2+-doped hydrides and deuterides. The onset temperature of quenching (T 95 %) and the quenching temperature (T 50 %) were determined from photoluminescence intensities, and the energy barrier for thermal quenching was estimated. Then, a scheme with the localization of divalent and trivalent lanthanide 4f and 5d levels for the example LiSrH3 was proposed. In deuterides, the quenching temperatures are slightly higher than in hydrides, which can be related to the influence of the different phonon frequencies. In the TL measurements we observed very shallow and intense TL glow peaks in all samples. We also used density functional methods in order to show qualitative trends for the stability of possible defects. The model calculation suggest that energetically favorable defects are the introduction of Eu2+ on a Sr2+ or Ba2+ site, the substitution of barium by strontium and vice versa, lithium and hydrogen vacancies and combinations, and possibly clusters thereof. The observed persistent luminescence for several minutes despite of the lack of intense traps at room temperature suggests that the material could in principle be promising for the design of long-lasting phosphors, if traps could be stabilized to be released at higher temperature.

Imaging and therapeutic applications of persistent luminescence nanomaterials

“…To go in deeper understanding, knowledge of the energy formation of defects, defects stability and defects energy position are required, through band structure and defects calculations. 83 Several spectroscopic techniques have been used to study the persistent luminescence mechanism such as: optical, Electron Paramagnetic Resonance (EPR) to control the origin and defects intensity, 84 X-rays spectroscopies to give insight to the mechanism , 85 thermoluminescence and photoconductivity 86,87 to measure the traps depth. 88 In the case of electrons traps and holes traps, 89 the stored charges can be released by various processes, as presented in the following part of this review, such as thermal, 90 optical 91 or others physical stimulations, 92 resulting in stimulated emissions from the active recombination centers.…”

Recent Advances in Rare Earth‐Doped Hydrides

“…An increase of n from 1.6 to 2 is thus expected to more than double the radiative decay rate, which is in agreement with the observed decay rates in hydrides. Additionally, the Eu 2+ ‐doped inverse perovskites Li M H(D) 3 ( M = Sr, Ba) were also studied using thermally stimulated luminescence and shallow, intense glow peaks were observed . The results were compared to density functional calculations and models for different defect configurations in order to study qualitative trends for the stabilities of different possible defects.…”

Nephelauxetic effect of the hydride ligand in Sr2LiSiO4H as a host material for rare-earth-activated phosphors

“…For the past decades, hydrides and mixed anion hydrides containing Eu 2+ dopant have been reported to exhibit green-red luminescence. 10,[14][15][16][17][18][19][20] However, their poor stability in air and moisture limits their application. In contrast, we have recently demonstrated that oxyhydride GdHO is stable in ambient air and can act as a phosphor host for Tb 3+ .…”