Mechanisms of Photoluminescence in Copper-Containing Fluoride Borate Crystalsстатья
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Дата последнего поиска статьи во внешних источниках: 15 февраля 2024 г.
Авторы:
Inerbaev Talgat M.,
Han Yulun,
Bekker Tatyana B.,
Kilin Dmitri S.
Аннотация:Mechanisms of photoluminescence in antizeolite fluoride borates (AFBs) doped by
copper ions are interpreted based on a comparison between experimental and computational
approaches. Doped AFBs demonstrate the effect of thermally stimulated photoluminescence and hold
a promise for the use as radiation detectors. AFBs are built of porous framework [Ba12(BO3)6]6+ with
channels along the c axis. Lattice channels can accommodate various guest anionic groups. In this
study, we present the results of modeling the electronic and optical properties of Cu-containing
fluoride borates with [Cu(OH)4]3− (monovalent Cu) and [Cu(OH)6]4− (divalent Cu) as anionic
groups. It is found that monovalent Cu+ ions create occupied Cu-3d states near the top of the valence
band, whereas divalent Cu2+ ions create vacant Cu-3d states near the bottom of the conduction band.
These states can serve as traps for electronic excitations and affect both the linear absorption and
photoluminescent (PL) properties. PL spectra calculations were performed using two ab initio
methodologies: (i) molecular dynamics (MD) sampling and (ii) time integration along with the
progression of subsequently occupied excited states. The results show that the theoretical PL spectra
calculated at a temperature of 10 K are instrumental in interpretation of experimental data obtained at
77 K. This effect is due to the strong dependence of Cu−OH distances in anionic groups along MD trajectories at given
temperatures, which, in addition, manifests itself in the temperature dependence of the times and relaxation paths of electronic
excitations. The results obtained open the way to designing new materials with predetermined properties for applications in radiation
detectors based on thermally stimulated photoluminescence.