Photoluminescence behavior of the Sm3+ and Tb3+ ions doped into the Gd2(WO4)3 matrix prepared by the Pechini and ceramic methods

Abstract

The Gd 2 (WO 4 ) 3 :RE 3+ compounds (where RE 3+ = Sm and Tb) were prepared by the Pechini and ceramic methods and characterized by X-ray diffraction and infrared spectroscopy. These rare earth materials present high orange (Sm 3+ -compound) and green (Tb 3+ -compound) luminescence intensity under UV radiation. The excitation spectra of these compounds presented broad bands arising from ligand-to-metal charge transfer (O→W and O→RE 3+) and narrow bands from 4f-intraconfigurational transitions. The excitation spectra of Tb 3+ system also exhibit broad bands attributed to the interconfigurational transition (4f-5d). The emission spectra exhibited the , respectively, while a broad band assigned to the LMCT (O→W) is observed when the excitation is monitored on the O→W LMCT state around 270 nm. The experimental intensity parameters η Sm and η Eu present similar behaviors, suggesting that the Sm 3+ ion is in a highly polarizable chemical environment with similar covalent character of the metal-donor atom interaction to the tungstate doped europium system. The cross-relaxation process from the 5 D 3 to the 5 D 4 levels of the Gd 2 (WO 4 ) 3 :Tb 3+ system has been also reported.

Novel Eu3+-doped red-emitting phosphor Gd2Mo3O9 for white-light-emitting-diodes (WLEDs) application

“…2): the broad excitation band extending up to 350 nm is attributable to the charge transfer transition of MoO 4 2− and Eu-O group, and the narrow peaks located at wavelengths longer than 350 nm can be assigned to the f-f transitions of Eu 3+ . The f-f transitions of Eu 3+ in excitation spectrum include sharp lines 7 F 0 → 5 L 6 (Eu 3+ ) at 395 nm, 7 F 0 → 5 D 2 (Eu 3+ ) at 465 nm, and 7 F 0 → 5 D 1 (Eu 3+ ) at 535 nm; their intensities are comparable to the broad C-T band (in Fig.…”

“…This abnormal phenomena was also observed in NaM(WO 4 ) 2−x (MoO 4 ) x :Eu 3+ (M = Gd, Y, Bi) [7] and AgLnMo 2 O 8 [16] . Probably, this is due to the nature of WO 4 2− and MoO 4 2− groups. The emission spectrum of Gd 1.8 Mo 3 O 9 :Eu 0.20 3+ excited by 280 nm was shown in Fig.…”

“…As important optical materials, tungstates and molybdates have attracted particular interest because of their importance in practical applications as laser host materials in quantum electronics [1], scintillators in medical devices [2,3] and phosphor materials in fluorescent lamps, cathode ray tubes and X-ray intensifying screens [4]. In the last decades, a large number of rare earth-doped luminescent materials have been extensively investigated.…”

“…From then on, exploiting phosphors, which can be efficiently excited by blue and/or NUV light, became a very active and interesting research subject. Host candidates such as molybdates and tungstates, attract much attention because of some special properties of MoO 4 [13].…”

Study of the annealing temperature effect on the structural and luminescent properties of SrWO4:Eu phosphors prepared by a non-hydrolytic sol–gel process

“…Optical properties of trivalent rare earth (RE 3+ ) ions in tungstate materials with a scheelite structure have been widely investigated [1]. There has been significant interest in studying the interactions between (RE 3+ ) ions in solids.…”