Luminescence Properties of Dual Valence Eu Doped Nano-crystalline BaF2 Embedded Glass-ceramics and Observation of Eu2+ → Eu3+ Energy Transfer

Abstract

Europium doped glass-ceramics containing BaF(2) nano-crystals have been prepared by using the controlled crystallization of melt-quenched glasses. X-ray diffraction and transmission electron microscopy have confirmed the presence of cubic BaF(2) nano-crystalline phase in glass matrix in the ceramized samples. Incorporation of rare earth ions into the formed crystalline phase having low phonon energy of 346 cm(-1) has been demonstrated from the emission spectra of Eu(3+) ions showing the transitions from upper excitation states (5)D(J) (J = 1, 2, and 3) to ground states for the glass-ceramics samples. The presence of divalent europium ions in glass and glass-ceramics samples is confirmed from the dominant blue emission corresponding to its 5d-4f transition under an excitation of 300 nm. Increase in the reduction of trivalent europium (Eu(3+)) ions to divalent (Eu(2+)) with the extent of ceramization is explained by charge compensation model based on substitution defect mechanisms. Further, the phenomenon of energy transfer from Eu(2+) to Eu(3+) ion by radiative trapping or re-absorption is evidenced which increases with the degree of ceramization. For the first time, the reduction of Eu(3+) to Eu(2+) under normal air atmospheric condition has been observed in a BaF(2) containing oxyfluoride glass-ceramics system.

Enhanced near‐infrared to green upconversion from Er3+‐doped oxyfluoride glass and glass ceramics containing BaGdF5 nanocrystals

“…For all the samples, sharp excitation bands at 356, 363, 378, 406, 443,450, 486, and 522 nm are observed due to transitions from ground state to 4 G 9/2 , 4 G 11/2 , ( 2 G, 4 F, 2 H) 9/2 , 4 F 5/2 , 4 F 7/2 , 2 H 11/2 , 4 S 3/2 energy levels of Er 3+ ions, respectively. Similar broad emission band in oxyfluoride glass/glass ceramics has been reported in Eu 3+/ Eu 2+ -doped systems by our group 14,19 , and the origin of the broad band was attributed to the transition from 4f to 5d level of Eu 2+ ions. Additionally, in the BaGdFG glass and BaGdFGC glass ceramics, the presence of excitation bands at 275 and 311 nm resulting from 6 I J and 6 P 7/2 levels of Gd 3+ ions, respectively, indicates energy transfer process from Gd 3+ to Er 3+ .…”

Surface Characterization and Photoluminescence Properties of Ce3+,Eu Co-Doped SrF2 Nanophosphor

“…The presence of both Eu oxidation states therefore strongly enhanced the emission intensity of the Eu 3+ ions. Detailed investigations on the luminescence phenomenon of Eu 3+ and Eu 2+ have previously been studied by various workers [10,29,30,31]. …”

Czochralski growth and optical properties of SrB2O4:Eu2+ single crystals

“…Energy transfer from excited Eu 2 þ to Eu 3 þ has been observed in Ref. [14] where upon excitation into broadband of Eu 2 þ at 360 nm, the strong luminescence at 610 nm has been observed.…”