Photostimulated Luminescence and Optical Storage in Eu ^(2+)-Doped Fluoride-Oxide Glass Ceramics

Photostimulated luminescence (PSL) phenomenon was observed in a fluoride-oxide glass ceramics doped with Eu 2+. When the UV light irradiated glass ceramic was stimulated by a longer wavelength light, PSL at 447 nm due to the 5d-4f transition of Eu 2+ was observed. The PSl excitation band peaking at 543 nm is due to the electron trap centers which are located either in the Eu 2+-doped crystallites or in the glass; where exactly they are located in is not yet known. The optical storage properties of this kind of glass ceramic were also studied. By comparing with the investigations on PSL phosphor Eu 2+ doped alkali halides, PSL mechanism in glass ceramics which is still an open question and has to be investigated in further experiments was explained.

Photostimulated Luminescence and F-centers of Sr_3Ca_2(PO_4)_3X:Eu^(2+)(X=F,Cl,Br)

This paper reports the F-centers and photostimulated luminescence of Eu^(2+)-activated Sr_3Ca_2(PO_4)_3X crystals.The influence of various halide ions on the F-centers and their energy level is discussed.The mechanism for the photostimulated luminescence and valence change of Eu ion in that process have been investigated.

MECHANISM FOR PHOTOSTIMULATED LUMINESCENCE (PSL) OF BaFX: Eu2^+

Some new photostimulable F centers in the X-rayed BaFX: Eu2^+ were found. Their absorption bands are located in IR region. PSL process of X-rayed BaFX:Eu^(2+) consists of two subordinated process—e^--h^+ recombination and radiative transition of Eu2^+ ions. The latter is a slow and rate-determining step. Dynamics and mechanism of that PSL have been investigated.

PHOTOSTIMULATED LUMINESCENCE ON BaFCl: Eu^(2+) THIN FILM

In this paper, we have succesfully prepared the sample of BaFCl: Eu2+thin film using the vacuum thermal evaporation method and first studied photostimulated luminescence on BaFCl: Eu2+thin film.

Long persistent and photostimulated luminescence properties of Sr_2Al_2SiO_7:Eu^(2+)/Tm(3+) phosphors

A series of Sr2A12SiO7 phosphors with fixed Eu2＋ concentration and various Tm3＋ concentrations were synthesized via a high temperature solid state reaction. The structure and luminescence properties of the samples were characterized by X-ray powder diffraction （XRD）, photoluminescence （PL） spectra, decay curves, thermoluminescence （TL） glow curves as well as the photostimu- lated luminescence （PSL） spectra. Sr2A12SiO7：Eu2＋,Tm3＋ phosphors exhibited strong green phosphorescence and photostimulated lu- minescence originating from 4f65d1-4f7 transition of Eu2＋ after ultraviolet light stimulation. Deep traps were found by analyses on the phosphorescence decays and thermoluminescence spectra. It was also found that with increasing the time interval between UV excita- tion turn-off and stimulation turn-on, the photostimulated luminescence became stronger. This phenomenon resulted from the fact that the captured electron was retrapped by the deep traps. Compared with the Tm3＋-free sample, it was found that the PSL intensity was strongly enhanced in Tm3＋ eodoping samples.

Luminescence property of Eu-doped fluorochlorozirconate glass-ceramics

A series of Eu2＋-doped fluorochlorozirconate glass-ceramics were prepared by solid state reaction method. X-ray diffraction, pho- toluminescence, photo-stimulated luminescence （PSL） and the turbidity of fluorozirconate glass containing BaCl2 nano- and micro-crystals were measured for the samples annealed at 290℃ for 10 rain The PSL was attributed to the characteristic emission of Eu2＋ in nano-crystallites of BaCI2, which formed in the glass upon annealing. The PSL efficiency of the glass ceramic was increased by increasing the concentration of BaCl2, which, however, resulted in the decreasing in the transparency of the sample. The sample turned to a semi-transparent glass ceramic or even an opaque and milky white one from a near-transparent glass. The trade-off between optical transparency and PSL intensity over different concentrations of BaCl2 for X-ray imaging plate applications was briefly discussed.

Luminescence studies of MBrCl:Eu^(2+) (M=Ca,Sr,Ba)

Europium doped MBrCl （M=Ca, Sr, and Ba） phosphors were prepared by solid state reaction in reductive atmosphere. Photolu- minescence （PL）, photostimulated luminescence （PSL） after X-ray irradiation and optical absorption studies of MBrCI：Eu2＋ （M=Ca, Sr, and Ba） revealed that： （1） blue light emission, under the excitation of 300 nm, was observed in all these phosphors; （2） the shape of the emission spectra in CaBrCI：Eu2＋ could be changed by varying the bromine/chlorine ratio during synthesis, while that in SrBrCI：Eu2＋ and BaBrCI：Eu2＋ showed no change; and （3） PSL was observed in SrBrCI：Eu2＋ and BaBrCI：Eu2＋ after X-ray irradiation. Difference absorption spectrum （DAS） in SrBrCl：Eu2＋showed two broad bands centered at about 470 and 570 nm, and DAS in BaBrCl：Eu2＋showed two bands at about 550 and 675 nm, respectively. This enabled the use of He-Ne laser （633 nm） or even semiconductor fight-emitting diodes （LED） instead of gas lasers for photostimulation.

Study of Photostimulable Luminescence Materials Sr_9Ca(PO_4)_6Cl_2:Eu

The polycrystalline Sr_9Ca(PO_4)_6Cl_2:Eu has been synthesized by solid state reaction.The reaction condition,the appropriate raw materials and their quantity used,which may affect the photostimulable luminescence (PSL),have been systematically inves- tigated.The properties of this PSL phosphor as a material for storing and reproducing the X-ray image in computer-aided radiography have been reported briefly.

Colour Centres and Energy Transfer in BaF_(2-x)Cl_x∶Eu^(2+) Phosphors

The optical absorption spectra of BaF2-x Clx ：Eu^2＋ after ultraviolet （UV） light excitation were investigated. The differences between the absorption spectra after and before excitation （DAS） were observed. The DAS increase at both the high and the low energy side of F band in BaF2-xClx ： Eu^2 ＋ after 245 nm UV light excitation. The bleach effect of UV light and the absorption of electrons in the valence band may account for the former and the formation of Fa centres （association of F（Cl^-） centres）, whose absorption band matches the HeNe laser better, may explain the latter. In the write-in process, the transfer of electrons is via tunneling, In the readout process, the transfer of electrons captured in F（F^-） and Fa centres is more likely via tunneling, and that of F（Cl^- ） centres is more likely via conduction band.

Effect of TSL and PSL in Al^(3+)-Doped BaFBr∶Eu^(2+) at Difference Synthesis Conditions

Thermal stimulated luminescence (TSL) and photostimulated luminescence (PSL) were used to investigate the luminescent performance of Al 3+ doped BaFBr∶Eu 2+ in different synthetic conditions. Theory analysis shows that the decay of TSL spectra is different from that of PSL spectra. Theoretical calculation was used to investigate the effects of energy state in Al 3+ doped BaFBr∶Eu 2+ by different synthetic conditions. The relationship of color center’s energy and different synthetic conditions is discussed.

A New Promising X-Ray Storage Phosphor BaBrCl∶Eu^(2+)

Photostimulated luminescence was observed in X-ray irradiated BaBrCl doped with Eu^2 ＋ . It shows an emission band that peak at 413 nm, and two difference absorption spectra （DAS） bands that peak at - 550 nm and 675 nm respectively. The stimulation energy is lower than that of BaFX：Eu^2＋ （X = Cl, Br）, and matches the cheaper, more portable, and more convenient semiconductor laser better. The results indicate that BaBrCl ： Eu^2＋ shows positive potential as a promising X-ray storage phosphor for practical utilization.