The influence of co-doping on the luminescence and thermoluminescence properties of Cu-containing fluoride borate crystalsстатья
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Дата последнего поиска статьи во внешних источниках: 15 февраля 2024 г.
Аннотация:The results of this study provide data on the luminescence and thermoluminescence properties of fluorideborate Ba12(BO3)6[BO3][LiF4] crystals co-doped with copper, rare earth elements, and strontium. Thecrystals were grown from high temperature solutions. This study revealed a considerable difference indecay time: about 60 ns for Cu+ photoluminescence at 412 nm in Ba12(BO3)6[BO3][LiF4]:Cu crystals afterexcitation at 263 nm, and about 1.8 ms for Eu3+ photoluminescence at 612 nm in Ba12(BO3)6[BO3][LiF4]:Cu,Eu crystals after excitation at 300, 325, and 395 nm. The absence of short-wavelength luminescence ofCu+ centers in photoluminescence spectra under 325 nm excitation in Ba12(BO3)6[BO3][LiF4]:Cu,Eu andBa12(BO3)6[BO3][LiF4]:Cu,Eu,Tb,Ce crystals is associated with the nonradiative energy transfer from theexcited electronic state of Cu+ ions to the energy levels of the rare earth elements. Thethermoluminescence curves of these crystals lack a peak associated with capture centers. Co-doping withcopper and strontium (Ba12(BO3)6[BO3][LiF4]:Cu,Sr, P42/mbc, a = 13.5174 (3) Å, c = 14.9399 (3) Å) has anoticeable effect on both photo- and thermoluminescence properties. This fosters the formation of deepercapture centers and promotes an increase in the temperature interval between thermoluminescencepeaks, which is essential for the stable storage of dosimetric information. First-principles density functionaltheory investigation indicates that the presence of monovalent copper ions narrows the bandgap widthcompared to that of undoped Ba12(BO3)6[BO3][LiF4] crystals due to the transitions from the Cu-3d to Ba-5dlevels. The presence of bivalent copper in the structure results in unfilled defect levels inside the bandgap.This contributes to the absorption in the visible range due to the electronic transitions from the O-2p toCu-3d levels.