(Y0.95La0.05)2O3: Ce3+ nano-powder was synthesized by co-precipitation method and sintered at 800 and 900 oC. All the samples were cubic phase characterized by X-ray diffraction (XRD) analysis. The samples sintered at the lower temperature exhibited luminescence. According to the distinguishable structure of Ce 3d peaks and the shift of O 1s lines in the X-ray photoelectron spectroscopy (XPS), luminescence was further confirmed to originate from Ce3+ ions. Effects of introducing La3+ into Y2O3 were discussed and it showed that under 800 oC calcining, the existing of La3+ made it more easy for Ce3+ to dope into the host lattice.
The precursor powders of LuAG∶Ce3+ transparent ceramics were synthesized by solvo-thermal method.The crystal structure and morphology of powders were analyzed by means of Fourier transform infra-red spectroscopy,X-ray diffraction and scanning electron microscopy.The precursor powders were sintered into transparent ceramics in vacuum and then in nitrogen without any additive.The surface morphology of the transparent unpolished ceramics was characterized using scanning electron microscopy.Some factors that affect the transparency of ceramics were discussed.The UV-Vis fluorescence excitation and emission spectra of LuAG∶Ce3+ transparent ceramics were measured.The vacuum ultraviolet spectra of transparent ceramics were investigated using the synchrotron radiation as the excitation source.The excitation mechanism of Ce3+ was discussed at different excitation wavelength.
WANG Lin-xiangZHU Heng-jiangWU Ling-yuanDENG Kai-moGUO Chang-xinYIN Min
Lutetium aluminum garnet(LuAG) precursors doped with different Pr3+ concentration(0.25at.%,0.5at.%,1.0at.%,3.0at.%,5.0at.%) were synthesized via a co-precipitation method using ammonium hydrogen carbonate as precipitant. The phase evolution and morphology of the precursor were characterized with X-ray diffractometer(XRD) and transmission electron microscopy(TEM) . The resultant LuAG:Pr3+ powder was sintered into translucent ceramic without any additives in vacuum at 1150 °C and then in nitrogen atmosphere at 1700 °C. Photoluminescence spectra of LuAG:Pr3+ powder and ceramic were measured at room temperature in vacuum ultraviolet(VUV) and ultraviolet(VU) region. For the 5d-4f transition of Pr3+ ions,dominant emission of ceramic samples peaking round 311 nm had higher luminescence intensity. And the host absorption in ceramic samples was not as intensive as that in powder samples. The luminescent intensity of LuAG:Pr3+ varied with the Pr3+ contents and the quenching concentration was about 1.0at.% for ceramic and 3.0at.% for powder,which was much higher than 0.24at.% for LuAG:Pr3+ single crystals. This phenomenon showed that the ceramic had some superiority over single crystals.
Under 980 nm laser excitation,red emission(5D0-7FJ(J=0,1,2)) of Eu3+ was observed in cubic Y2O3 codoped with Eu3+ and Yb3+.The dependence of the upconverted emission on doping concentration and laser power was studied.Yb3+ emission around 1000 nm(2F5/2-2F7/2) was reported upon excitation of Eu3+ ions.The decay curves of 5DJ(J=0,2) emission of Eu3+ under excitation of 266 nm pulse laser were examined to investigate the Eu3+→Yb3+ energy transfer process.Cooperative energy transfer process was discussed as the possible mechanism for the visible up-conversion luminescence of Eu3+ and near-infrared down-conversion emission of Yb3+.
Bi^(3+) and Yb^(3+) codoped cubic Y2O3 phosphors are prepared by pechini sol-gel method.Strong near-infrared (NIR) emission around 980 nm from Yb^(3+)(2F5/2 → 2F7/2) is observed under ultraviolet light excitation.A broad excitation band ranging from 320 to 360 nm,owing to the 6s 2 →6s6p transition of Bi^(3+) ions,is recorded when the Yb^(3+) emission is monitored,which suggests a very efficient energy transfer from Bi^(3+) ions to Yb^(3+) ions.The Yb^(3+) concentration dependences of both the Bi^(3+) and the Yb^(3+) emissions are investigated.The decay curve of Bi ^(3+) emission under the excitation of 355 nm pulse laser is used to explore the Bi^(3+) →Yb^(3+) energy transfer process.Cooperative energy transfer (CET) is discussed as a possible mechanism for the near-infrared emission.
Polycrystalline LuAG:Ce3+(cerium3+-doped lutetium aluminum garnet) powders were prepared by mixed solvo-thermal method.Fourier-transform IR spectroscopy(FTIR) and X-ray diffraction(XRD) measurements showed that the precursors were ethanol derivatives AlO(OH) crystal with hydroxyl and carbonate group.XRD results showed that phase of Lu2O3 disappeared with the precursors were annealed at 400 °C,cubic phase LuAG:Ce3+ appeared but only one diffraction peaks of LuAP(LuAlO3) at calcination temperature to 700 °C,and the purified crystalline phase of LuAG:Ce3+ was obtained at 1000 °C.The scanning electron microscopy(SEM) analysis revealed that the synthesized LuAG:Ce3+ powders were uniform and had good dispersivity with an average particle size about 100 nm.Excitation and emission spectra of Ce3+ doped LuAG phosphors were measured.Many factors of affecting the intensity of emission spectra were discussed.
