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

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• 作者：Nathalie KunkelAtul D. Sontakke ; Stephan Kohaut ; Bruno Viana ; Pieter Dorenbos
• 刊名：Journal of Physical Chemistry C
• 出版年：2016
• 出版时间：December 29, 2016
• 年：2016
• 卷：120
• 期：51
• 页码：29414-29422
• 全文大小：540K
• ISSN：1932-7455

文摘

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 (T₉₅ %) and the quenching temperature (T₅₀ %) 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.