Enhanced multimodal behaviour of Tm3+/Yb3+ co-doped YTaO4 ceramic material through Bi3+ activation and sensitization: Application as a spectral converter

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

“…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.…”

“…However, due to the distorted VO 4 3− , NbO 4 3− , and TaO 6 7− complexes, geometric relaxation for MMCT is much larger than that for the A band, leading to lower energy for the MMCT state than that for the A band state at their corresponding equilibrium geometric structures, which leads to the MMCT emission. It is worth noting that apart from the strong band at about 290 nm, a relatively weak band peaking at 257 nm is also observed in the excitation spectrum of YTaO 4 :Bi 3+ , 14 which can be identified as MMCT excitation without ambiguity. Similar luminescence phenomena, i.e., excitation bands peaking at 250 and 290 nm, are also observed in M-structure YTaO 4 :Bi 3+ .…”

“…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 .…”

“…Rare-earth vanadates, niobates, and tantalates have been widely employed as hosts for lanthanide-ion-activated luminescent materials, where the sensitization by host excitation provides an effective way to overcome the low absorptions of parity forbidden 4f–4f transition of trivalent lanthanide (Ln 3+ ) ions, which emanate highly efficient luminescence of Ln 3+ ions in different spectral regions, leading to broad applications, such as in lighting, − laser crystals, , optical thermometry, , bioimaging, and photodynamic therapy. − Meanwhile, efficient sensitization of Bi 3+ in Bi 3+ –Ln 3+ codoped vanadates, niobates, and tantalates has also been extensively reported. − Hence, an understanding of the intrinsic and Bi 3+ -related excited-state properties in rare-earth Group VB oxides is significant for the design and optimization of related materials.…”

Phase-sensitive radioluminescence and photoluminescence features in Tm3+-doped yttrium tantalates for cyan and white light generation

“…Light sources have been under steady development all the way throughout human existence, from ancient times to modern technology, culminating in the next generation of solid-state lighting: white light-emitting diodes (w-LEDs). 1,[12][13][14] Compared to the conventional incandescent and fluorescent lamps, the w-LED-based sources can offer outstanding benefits in terms of high luminous efficiency and reliability, which promises significant reductions in power consumption and pollution from fossil fuel power plants, in other words, eco-friendliness. 15,16 Among numerous outstanding properties, white-light LEDs also stand out by their mercuryfree composition, easy manufacturability, small volume, long durability and so on.…”