Synthesis and enhancement of luminescence intensity by co-doping of M+ (M=Li, Na, K) in Ce3+ doped strontium haloborate (original) (raw)
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Materials
The present study is aimed at unveiling the luminescence potential of Ba4−xSr3+x(BO3)4−yF2+3y (BSBF) crystals doped with Eu3+, Tb3+, and Ce3+. Owing to the incongruent melting character of the phase, the NaF compound was used as a solvent for BSBF crystal growth. The structure of BSBF: Eu3+ with Eu2O3 concentration of about 0.7(3) wt% was solved in the non-centrosymmetric point group P63mc. The presence of Eu2O3 in BSBF: Eu3+ leads to a shift of the absorption edge from 225 nm to 320 nm. The photoluminescence properties of the BSBF: Ce3+, BSBF: Tb3+, BSBF: Eu3+, and BSBF: Eu3+, Tb3+, Ce3+ crystals have been studied. The unusual feature of europium emission in BSBF is the intensively manifested 5D0→7F0 transition at about 574 nm, which is the strongest for BSBF: Eu3+ at 370 nm excitation and for BSBF: Eu3+, Tb3+, Ce3+ at 300 nm and 370 nm excitations. No evidence of Tb3+→Eu3+ energy transfer was found for BSBF: Eu3+, Tb3+, Ce3+. The PL spectra of BSBF: Eu3+ at 77 and 300 K are simila...
Synthesis and photoluminescence of Strontium Silicate doped with Ce3+ and Li+
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Chemical Physics Letters, 2006
This paper reports the photo-luminescence spectroscopic results of Strontium-Barium-Niobate, Sr x ,Ba 1Àx Nb 2 O 5 (SBN, x = 0.61 for near congruent composition) crystals doped with Cr 2 O, at cryogenic temperature (20 K). The experimental results reveal the need of reassignment of the Cr 3+ ions defect centres in this material. For first time, a broad emission band in the near infrared region centred at ca. 950 nm is reported. This emission band has micro-seconds decaytime constant and a FWHM band-width > 1700 cm À1 and has been ascribed to the vibronically assisted 4 T 2 ! 4 A 2 transition. A much narrower emission band centred at ca. 764 nm with milli-seconds decaytime constant and a FWHM band-width of ca. 170 cm À1 is correlated to the 2 E ! 4 A 2 radiative transition (R-line).
VUV–Vis Luminescent Properties of BaCaBO 3 F Doped with Ce 3+ and Tb 3+
The Journal of Physical Chemistry C, 2013
The BaCaBO 3 F wide band gap host and the charge-compensated phosphors BaCaBO 3 F:Ln 3+ (Ln = Ce, Tb, Gd) and BaCaBO 3 F:Ce 3+ ,Tb 3+ have been synthesized by a solid-state reaction method at high temperature. Their spectroscopic properties in the vacuum ultraviolet (VUV)−vis range have been investigated. The band gap of the host lattice is estimated at 7.8 eV, which is considerably higher than the value found from its diffuse reflectance spectrum. The 5d crystal field level locations, Stokes shift, and Huang−Rhys factor have been determined from the VUV excitation and near-UV emission spectra of BaCaBO 3 F:Ce 3+ . The 5d 1 decay lifetime is 29 ns at x ∼ 0.005. Concentration quenching occurs for Ba 1−2x Ce x Na x CaBO 3 F with maximum intensity at x ∼ 0.035 and with critical distance R c = 17.7 Å. An unusual broad, intense band in the excitation spectrum of BaCaBO 3 F:Gd 3+ is assigned to a near-defect exciton. Very weak emission from 5 D 3 , and intense green emission from 5 D 4 , has been assigned for BaCaBO 3 F:Tb 3+ . In the VUV region, the spin-allowed and the spin-forbidden 4f 8 → 4f 7 5d transitions are observed. The codoped system BaCaBO 3 F:Ce 3+ ,Tb 3+ exhibits emission color tunability when varying the excitation wavelength or the dopant ion concentration. The energy transfer from Ce 3+ to Tb 3+ takes place in the fast migration regime with k ET ∼ 10 6 − 10 7 s −1 and with energy-transfer efficiency up to 23% for the samples investigated. The mechanism is revealed from energy level and decay measurements. This codoped system exhibits absorption bands near the major Xe discharge wavelengths.
Effect of boron substitution on the preparation and luminescence of Eu2+ doped strontium aluminates
Journal of Alloys and Compounds, 2004
A series of monoclinic strontium aluminates, SrAl 2−x B x O 4 :Eu 2+ (0 ≤ x ≤ 0.3), were prepared by a solid state reaction. The effect of boron on the preparation, structure and luminescence was studied by thermoanalytical, X-ray powder diffraction (XPD), UV excited as well as thermoluminescence (TL) methods. Boron decreased clearly the reaction threshold temperature but concentration was not found important. Boron decreased also the amount of impurities. The monoclinic structure remained the same irrespective of the boron content. No Al-B solid solution was formed. The luminescence band position, shape, and width were not changed as a function of the boron content. The UV excited luminescence intensity was enhanced but persistent luminescence suppressed when the boron concentration increased. The thermoluminescence peak shifted slightly towards lower temperatures and the TL intensity was suppressed by increasing boron concentration maybe due to the modification of trap concentration and depth.