Luminescence of Li6Gd(BO3)3 crystals upon ultraviolet and inner-shell excitations

Abstract

a b s t r a c tThe paper presents the results of the study on luminescence and electronic excitations in Li 6 Gd(BO 3 ) 3 single crystals. The optical and luminescence spectroscopy with a sub-nanosecond time resolution upon selective photoexcitation in the energy range from 3.0 to 650 eV was used to investigate in detail the luminescence of both the Gd 3 þ host ions and Ce 3 þ impurity ions as well as the processes of energy transfer between them. The intrinsic ultraviolet emission at 3.95-3.97 eV due to 6 P j -8 S 7=2 transitions in the Gd 3 þ host ion and the fast luminescence at 2.8-3.0 eV due to 5d-4f 1 dipole-allowed transitions in the Ce 3 þ impurity ion were studied upon excitations through the intracenter, charge transfer, bandto-band, and inner-shell transitions. The specificity of the energy transfer upon excitation of photoluminescence in the energy range of absorption of the inner shells of different atoms of the crystal, as well as in the energy region of the giant resonance of 4d-4f transitions was revealed. On the basis of the experimental data, the bandgap E g ¼9.3 eV, the minimum energy of the 5d-4f 1 and charge transfer transitions were determined. The expected positions of the ground states of the 4f n and 4f nÀ1 5d levels of trivalent lanthanide ions as well as the 4f n þ 1 and 4f n 5d levels of divalent ions were calculated for all the lanthanide ions in Li 6 Gd(BO 3 ) 3 host crystal.

A far ultraviolet spectroscopic study of the reflectance, luminescence and electronic properties of SrMgF4 single crystals

“…For example, the charge-transfer transitions O-Gd are responsible for a PLE band at 6.8 eV, which dominates in PLE spectrum of intrinsic luminescence in Li 6 GdB 3 O 9 crystals. At the same time, the optical transitions because of the excitonic absorption appears only in the reflection spectrum at 8-9 eV, whereas such transitions are almost completely suppressed in PLE spectrum of intrinsic luminescence in this crystal [34][35][36]. In this connection, interpreting the PL emission bands in the SMF crystal, we should bear in mind that the intrinsic luminescence bands can also be excited in the energy region of the charge-transfer transitions.…”

Electronic excitations and luminescence of SrMgF4 single crystals

“…Complex multicomponent crystals, where there are charge-transfer transitions between different fragments of the crystal structure, often exhibit an efficient excitation of intrinsic PL bands in the region of charge-transfer transitions, as well as the complete or partial suppression of the excitation of these bands in the excitonic region. For example, the intrinsic PL excitation spectrum of the Li 6 GdB 3 O 9 crystal is dominated by the band of O-Gd charge-transfer transitions at 6.8 eV, whereas the excitation band of the free exciton in the range of 8-9 eV appears only in the reflectivity spectrum and is almost completely suppressed in the intrinsic PL excitation spectrum [37][38][39]. Therefore, in the interpretation of bands in the PL spectra of the SMF crystal, it should be remembered that the intrinsic PL bands of SMF can also be excited in the energy region of the charge-transfer transitions.…”

Scintillation properties of Li6Y0.5Gd0.5(BO3)3: Ce3+ single crystal

“…LYBO crystal has the ability to become a good scintillation detector and lasing material [11,17]. LGBO crystal has the potential to be used as a radiation detector due its good scintillation and luminescence properties [10,18,19]. 6 Li, 10 B, 157 Gd, 155 Gd isotopes interact with thermal neutrons that produce charged particles and γ-rays with MeV energy, which are capable of exciting some luminescence centers in the crystal lattice and emit signals to be detected by the optical sensors [20].…”