Origin of luminescence in Bi3+ - doped lanthanide niobates

Baran, M.; Беликов, К. Н.; Kissabekova, А.; Krasnikov, А.; Lushchik, A.; Mihóková, E.; Цюмра, В.; Vasylechko, L.; Zazubovich, S.; Zhydachevskyy, Yaroslav

doi:10.1016/j.jallcom.2020.157800

Cited by 13 publications

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“…15 Selftrapped excitons and the excitons trapped around Bi 3+ ions are identified to interpret the intrinsic emission and Bi 3+ -related emission, respectively. Interestingly, similar luminescence phenomena are also observed in (Y/Lu/Gd)NbO 4 :Bi 3+ and (Y/Lu/Gd)TaO 4 :Bi 3+ , 14,16,17 while the slight difference is the absence of intrinsic ultraviolet (UV) emission in GdTaO 4 . In addition, the intrinsic emissions of vanadates and niobates are in the visible wavelength range, while those of tantalates are in the UV range.…”

Section: Introductionsupporting

confidence: 59%

“…It is noted that the calculated excitation energy corresponds to the geometrically vertical transition to excite a triplet exciton, which should be lower than the excitation peaking energies of the valence-to-conduction interband transition. The difference is roughly estimated from the measured spectra at the scale a few 0.1 eV by the difference between peaking energies of the excitation band and optical band gap energies for the series of hosts. − ,− For a fair comparison, Table shows that the calculated excitation energies for vanadates are overestimated, while the emission energies are underestimated by 0.50–0.52 eV. In Section , we will show that this is related to the choice of mixing parameter α in the calculation.…”

Section: Resultsmentioning

confidence: 98%

“…As an important luminescence phenomenon, intrinsic luminescence has been widely reported in the (Y/Lu/Gd)(V/Nb/Ta)O 4 pure hosts. − The intrinsic blue luminescence is observed in vanadates and niobates, while UV emission is reported in tantalates. Self-trapped excitons have been identified to account for the intrinsic emission, but still, it remains unclear how the optically created excitons are self-trapped in the host crystal lattice.…”

Section: Resultsmentioning

confidence: 99%

“… a It is noted that the experimental data for vanadates, niobates, and tantalates are from refs − unless stated otherwise. b The value of 2.82 (eV) is the 440 nm emission reported in ref . c The value of 3.68 (eV) is the 337 nm emission from ref . d The value of 3.54 (eV) is the 350 nm emission from ref . e Excitation band peaking at 226 nm for the M-structure GdTaO 4 in ref is adopted as an approximation for the lacking data. …”

Section: Resultsmentioning

confidence: 99%

“…The supercells with new base-vectors ( a + b , a – b , 2 c ), (2 a , b , 2 c ), and (2 a , 2 b , 2 c ) containing 96 atoms were employed to model Bi-doped (Y/Lu/Gd)VO 4 , (Y/Lu/Gd)NbO 4 , and (Y/Lu/Gd)TaO 4 , respectively. The experimentally reported doping concentrations of Bi 3+ are 0.5–1 at.% in (Y/Lu/Gd)(V/Nb/Ta)O 4 . − Here, we replace one of the 16 (Y/Lu/Gd) 3+ ions in the supercell with a Bi 3+ ion to simulate the localized states of interest in Bi 3+ -doped (Y/Lu/Gd)(V/Nb/Ta)O 4 . Y (4s 2 4p 6 5s 1 4d 2 ), Lu (5p 6 6s 2 5d 1 ), Gd (5p 6 6s 2 5d 1 ), V (3s 2 3p 6 4s 1 3d 4 ), Nb (4s 2 4p 6 4d 5 ), Ta (5p 6 6s 1 5d 4 ), O (2 2 2p 4 ), and Bi (5d 10 6s 2 6p 3 ) were treated as valence electrons, and their interactions with the cores were described by the projector augmented wave method .…”

Section: Methods Of Calculationsmentioning

confidence: 99%

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Self-Activated and Bismuth-Related Photoluminescence in Rare-Earth Vanadate, Niobate, and Tantalate Series—A First-Principles Study

et al. 2021

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Rare-earth vanadates, niobates, and tantalates have shown self-activated and Bi 3+ -activated emissions. Their intrinsic emission has been attributed to self-trapped excitons (STEs), but the detailed information concerning the geometric and electronic structures of the excited states has remained unknown. Regarding the Bi 3+ dopants in these hosts, the luminescence has been attributed to two different mechanisms, i.e., Bi 3+ ↔ (V/Nb/Ta) 5+ metal-to-metal charge transfer and interconfigurational ( 3 P 0,1 → 1 S 0 ) transition. Here, first-principles calculations using hybrid functionals are employed to resolve these issues. The STEs are shown to be composed of an electron localized on an individual vanadium, niobium, or tantalum ion and a hole localized on a single nearest-neighbor oxygen ion that is not shared by covalent complexes, and the bond length of the (V/Nb/Ta)−O bond with oxygen accommodating the hole is significantly elongated. The Bi 3+ -related emission is identified as the recombination of an exciton with a hole and an electron localized correspondingly at Bi 3+ and (V/Nb/Ta) 5+ ions, while the excitation is dominated by the 6s → 6p transition of Bi 3+ . Furthermore, Bi 3+ has a hole trap level in all of the hosts considered with the trap levels in the vacuum-referred binding energy diagram being nearly flat but has an electron trap level only in rare-earth tantalates. Furthermore, the longwavelength emission observed in niobates and tantalates is interpreted based on our calculations to be excitons bound to intrinsic defects. The insights gained in this work deepen our understanding of the STEs and form the basis for interpreting similar luminescence phenomena in other ternary closed-shell d 0 transition-metal oxides. The clarification of Bi 3+ -related transitions and the analyses with the vacuum-referred binding energy diagram may find applications for the design and optimization of Bi 3+ -activated phosphors.

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Section: Introductionsupporting

confidence: 59%