| The advent of white light-emitting diodes(LEDs)was pregnant with a lighting revolution triggered by the development of semiconductor technology,following the microelectronics revolution.Due to the advantages of small size,vibration resistance,fast response speed,long service life and no pollution,LED would become the fourth-generation light source replacing incandescent lamp,fluorescent lamp and high-intensity gas discharge lamp.Green-lightemitting fluorescent powder was an important part to realize LED white-light emission.In this study,Ce3+ and Tb3+ mono-doped and Ce3+,Tb3+ co-doped M3Al2O6(M = Ca,Sr,Ba)series aluminate fluorescent powder was synthesized by the high temperature solid-phase method,to analyze the crystal structure and the particle morphology,investigate the luminescence properties and explore the mechanism of action.The main contents of the study were as follows:(1)The crystal structure,the morphology and the emission spectra under the excitation of their strongest excitation wavelengths of the synthesized samples were compared at different target reaction temperatures,and the effects of calcination temperature on reaction products were investigated.The optimum calcination temperatures of Ca3Al2O6,Sr3Al2O6 and Ba3Al2O6 as fluorescent powder substrates were determined,with the optimum calcination temperature being 1400 ?,1200 ? and 1450 ?,respectively.By comparing the luminescence properties of the samples under different doping concentrations of Tb3+ and Ce3+,the optimum doping concentrations of Tb3+ and Ce3+ ions under the three substrates were 1 mol %,1 mol % and 2 mol % and 2 mol %,2 mol % and 4 mol %,respectively.(2)By comparing the excitation spectra of M3-x Al2O6 : x Tb3+ series fluorescent powder,it was observed that the peak position of excitation peak of the 4f8-4f75d1 exhibited gradual blue shift with the increase of ionic radii of Sr and Ba.Among the studied three kinds of M3Al2O6 : Tb3+ fluorescent powder,it was found that Ca3Al2O6 : Tb3+ had better luminescence intensity,thus Ca3Al2O6 : Tb3+ was more suitable for UV excitation as green fluorescent powder.(3)By comparing the effects of Li+,Na+ and K+ on the three kinds of fluorescent powder substrates,the most suitable charge compensators for each of the three substrates were found.The crystal structure of the samples was not changed by the addition of the three alkali metal ions.All the three alkali metal ions could improve the luminescence efficiency,of which Li+ ion was the most obvious.(4)In the case of M3A12O6 : Ce3+,there were 6 different lattice sites for alkaline-earth metal ion M2+.The lattice sites occupied by the doping of Ce3+ in three kinds of M3A12O6 were analyzed by spectral analysis.(5)For Ca2.94Al2O6 : 0.06 Ce3+ and Ba2.94Al2O6 : 0.06 Ce3+,in the range of Tb3+ quenching concentration,the corresponding emission peak intensity of Ce3+ constantly decreased and Tb3+ luminescence intensities constantly increased with the increase of Tb3+ doping concentration;beyond the range of Tb3+ quenching concentration,the Tb3+ luminescence intensity constantly decreased with the increase of Tb3+ doping concentration,indicating that there was energy transfer between Ce and Tb.For Sr2.94Al2O6 : 0.06 Ce3+,the samples doped with Tb3+ failed to exhibit obvious Tb3+ luminescence under the excitation of Ce3+ excitation wavelength.The fluorescence lifetime suggested that radiation energy transfer may exist between Ce and Tb in M3Al2O6 structure matrix. |
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