Long-afterglow Phosphor Research Articles

Enhanced Long Persistence of Ca2MgSi2O7 : Eu2 + Yellow-Green Phosphors by Co-doping with Ce3 +

Long-afterglow phosphors were prepared by a solid-state reaction under a weak reductive atmosphere. Spectroscopy measurements demonstrated that energy transferred from to . The energy-transfer efficiency from to was 61%. Thermoluminescence measurement revealed that co-doped samples created much appropriate traps leading to the enhancement of the afterglow. The afterglow emission spectra revealed that in the co-doped samples acted as sensitizers and in (535 nm) acted as activators. The duration of co-doped samples was prolonged nearly two times compared with that of the single-doped sample. A possible afterglow mechanism was presented and discussed.

Energy transfer between Eu2+ and Mn2+ in long-afterglow phosphor CaAl2O4:Eu2+, Nd3+, and Mn2+

Long-afterglow phosphor CaAl2O4:Eu2+, Nd3+, and Mn2+ were prepared by the solid-state synthesis method. The CaAl2O4:Eu2+, Nd3+, and Mn2+ phosphors show two emission bands peaking at around 440 and 545 nm, originating from the allowed f-d transition of Eu2+ and the forbidden T41-A61 transition of Mn2+, respectively, under ultraviolet excitation at 340 nm. Spectroscopy and afterglow decay time measurements demonstrate that energy transfer from Eu2+ to Mn2+. The different colors between photoluminescence and afterglow was analyzed and observed based on energy transfer. Moreover, effects of Mn2+ doping on the afterglow properties of CaAl2O4:Eu2+, Nd3+ are explored and explained by thermoluminescence technique.

Effect of Dy on properties of red long-afterglow phosphor Sr3Al2O6:Eu2+,Dy3+

The red long afterglow phosphor Sr3Al2O6:Eu2+,Dy3+ was prepared by sol-gel method. The crystal structure was characterized by X-ray diffraction. The results reveal that the samples are composed of single Sr3Al2Ｏ6 phase at 1200℃, and the small amount of doped rare earth ions （Eu2＋ and Dy3＋） has no effect on the Sr3Al2Ｏ6 phase composition. The excitation, emission and afterglow spectra were investigated by fluorescence spectrophotometer technique. The broad excitation spectra in the range of 400—550 nm were found in the Sr3Al2Ｏ6:Eu2＋ and Sr3Al2Ｏ6:Eu2＋,Dy3＋ phosphors. The broad band spectrum is associated with defects and vacancies of host material and the peak at 530.1 nm can be assigned to the recombination of donor-acceptor pairs of Ｄy·Sr-V″Sr from dysprosium doping in the Sr3Al2O6. With the increasing concentration of Dy below 0.03, the emission intensity of Sr3-0．02-yAl2Ｏ6:0.02Eu2＋,yDy3＋ phosphors increases, and the samples exhibit the red light emission spectra with the main emission peak at 612 nm under an excitation of 473 nm. The red emission has a broad-band feature, belonging to the emission of the 4f65d1→4f7 of Eu2＋ions. With the increasing concentration of Dy within the range of 0.03—0.06, there was a new emission peak in the green region, and the emission intensities of the two peaks at 530 nm and 612 nm decrease. The afterglow time of the Sr2．95Al2Ｏ6:0.02Eu2＋,0.03Dy3＋ phosphors lasts 540s（≥1 mcd/m2） after removal of excitation. The Dy3＋ ions are auxiliary activator in the Sr3Al2O6:Eu2+,Dy3+ phosphors.

Eu2+ and Dy3+ co-doped Sr3Al2O6 red long-afterglow phosphors with new flower-like morphology

Abstract The detailed preparation process of Eu 2+ and Dy 3+ ion co-doped Sr 3 Al 2 O 6 flower-like phosphor powders with red long afterglow by a sol–gel method in the reducing atmosphere is reported. X-ray diffraction (XRD), scanning electron microscopy (SEM) and fluorescence spectrophotometer are employed to characterize the phosphor powders. The results reveal that Sr 3 Al 2 O 6 : x Eu 2+ , y Dy 3+ ( x =4, 8, 10, 20 mol%, y =10 mol %) phosphor powders calcined at 1200 °C for 2 h possess a Sr 3 Al 2 O 6 single cubic phase. The Sr 3 Al 2 O 6 :Eu 2+ , Dy 3+ crystallites show a new flower-like morphology. The excitation and emission spectra indicate that a broad excitation band chiefly lies in the visible range and that Sr 3 Al 2 O 6 :Eu 2+ , Dy 3+ phosphor powders exhibit a broad red emission band with emission peak at 612 nm under 472 nm excitation. Sr 3 Al 2 O 6 :Eu 2+ , Dy 3+ at the Eu 2+ concentration of 8 mol% shows the strongest luminescent intensity. Red long-afterglow phosphorescence is observed in the dark with naked eye after the removal of the excitation source.

Luminescence properties of a Tb 3+ activated long-afterglow phosphor

Luminescence properties of a new CaZnGe 2O 6:Tb 3+ long-afterglow phosphor, including photoluminescence, excited-state decay curve, long-afterglow decay curve, and thermoluminescence curve, have been investigated in this paper. Photoluminescence spectra analysis shows that the Tb 3+-doped CaZnGe 2O 6 phosphor emits intense green-lighting-emission from the 5D 3,4 to 7F J ( J = 6, 5, 4, 3) transitions. Moreover, the Tb 3+-related green-lighting-emission can last for more than 3 h after removal of the ultraviolet irradiation source. Both the excited-state decay curve and the long-afterglow decay curve of the Tb 3+-doped CaZnGe 2O 6 phosphor contain a fast decay component and another slow decay one. Thermoluminescence curve indicates that the incorporation of Tb 3+ ions into the CaZnGe 2O 6 host has produced suitable dense trapping centers with a thermoluminescence peak located at ca. 374 K, which is the origin of the long-afterglow phenomenon in this kind of material at room temperature. All the results indicate that the Tb 3+-doped CaZnGe 2O 6 phosphor has promising potential of practical applications.

Luminescence properties of a new Mn 2+-activated red long-afterglow phosphor

A new phosphor, CaZnGe 2O 6:Mn 2+, which emits red long-lasting phosphorescence centered at 648 nm upon UV light excitation, is prepared by the conventional high-temperature solid-state method and its luminescent properties are systematically investigated in this paper. XRD, photoluminescence, thermoluminescence spectra and afterglow decay curve are used to characterize the synthesized phosphor. This phosphor is well crystallized by calcination at 1150 °C for 3 h and possesses excellent performance. The color coordinate values of this phosphor are x=0.64, y=0.26 under 250 nm UV light excitation. Under 250-nm UV light irradiation, this phosphor shows obvious long-lasting phosphorescence that can be seen with the naked eye in the dark clearly after the irradiation source has been removed for more than 3 h. The possible mechanism of this red-light-emitting long-afterglow phosphor is also investigated based on the experiment results.

Luminescence Properties of a Pb2 + Activated Long-Afterglow Phosphor

Luminescence properties of long-afterglow phosphor, including photoluminescence, fluorescence lifetime, long-afterglow decay curve, and thermostimulated luminescence spectra, are investigated in this paper. Photoluminescence of the synthesized phosphor shows a single intense -related broadband emission located at . Moreover, the -related broadband emission still exists for more than , even after the ultraviolet irradiation source has been removed. Both the fluorescence and long-afterglow decay lifetime of the ions contain a fast decay component and slow decay one. Thermostimulated luminescence curve study indicates that the incorporation of ions into host produces two suitable dense trapping centers at 0.55 and , which is the origin of the long-afterglow phenomenon in this kind of material at room temperature. This finding has enlarged the activator of the family of long-afterglow phosphors available.

The valence of rare earth ions in R2MgSi2O7:Eu, Dy (R = Ca, Sr) long-afterglow phosphors

The valence of rare earth ions in R2MgSi2O7:Eu, Dy (R = Ca, Sr) long-afterglow phosphors was studies by L3 edge X-ray absorption near-edge structure (XANES) spectroscopy and photoluminescence spectroscopy. The results suggest that Eu ions are in a divalent and trivalent mixed-valence state while Dy ions exist in the trivalent state. No monovalent Eu and tetravalent Dy were observed. The applicability of a hole-transferring mechanism of long-afterglow phosphors is discussed. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)