添加S及掺杂Dy^(3+)对SrS:Eu^(2+)荧光粉发光性能的影响

采用高温固相法,以糊精为还原剂,在温度为1 150℃、N2-H2(10∶1)的还原气氛中合成了S、Dy^(3+)掺杂的SrS:Eu^(2+)红色荧光粉材料。采用X射线衍射分析(XRD)、荧光分光光度计等对其物相与光学性能进行表征。结果表明,样品在蓝光(波长498nm)激发下,添加的S的质量分数为2%时,SrS:Eu^(2+)荧光粉发出的红光强度最强;Dy^(3+)的掺杂摩尔分数为1%时,试样发出的红光最强。其激发光谱是400~600nm的宽带激发光谱。

Si_3N_4掺杂氮化对Sr_3SiO_5:Eu^(2+)荧光粉发光性能的影响

采用高温固相法制备Si_3N_4掺杂氮化Sr_(2.99)SiO_(5-6x)N_(4x):0.01Eu^(2+)荧光粉。采用XRD、EDS和SEM测试结果表明:N^(3-)进入Sr_3SiO_5基质晶格中取代部分O^(2-)离子,形成了单一相Sr_(2.99)SiO_(5-6x)N_(4x):0.01Eu^(2+)固溶体。PL&PLE荧光光谱测试结果显示,Sr_(2.99)SiO_(5-6x)N_(4x):0.01Eu^(2+)荧光粉在344nm紫外光的激发下发射出红橙光,属于Eu^(2+)离子典型的4f65d1?4f7电子跃迁。随着N浓度的增加,Sr2.99Si O5-6xN4x:0.01Eu^(2+)荧光粉发射光谱和激发光谱的强度明显增强。热稳定性测试结果表明,Si_3N_4掺杂氮化能够显著提高Sr3Si O5:Eu^(2+)荧光粉的热稳定性。通过Arrhennius模型拟合结果表明横向穿越过程(crossover)引起的Sr_3SiO_5:Eu^(2+)荧光粉氮化前后的温度猝灭。

Photoluminescent properties of Sr_2SiO_4:Eu^(3+) and Sr_2SiO_4:Eu^(2+) phosphors prepared by solid-state reaction method

Eu2＋ and （or） Eu3＋ doped Sr2SiO4 phosphors particles were synthesized by a conventional solid-state reaction technique, and their structural and optical properties were investigated. The X-ray diffraction （XRD） results showed that the obtained phosphors were composed of orthorhombic α′-Sr2SiO4 and monoclinic β-Sr2SiO4 phase. When excited under 256 nm, Sr2SiO4：Eu3＋ phosphors showed intense emission in the red region. Sr2SiO4：Eu3＋ phosphors exhibited white emissions （x=0.30, y=0.40, Tc=6500 K） ranging from 425 to 650 nm when it was excited by near-ultraviolet （near-UV） light, indicating that Sr2SiOn：Eu2＋ was a good light-conversion phosphor candidate for near-UV chip.

Synthesis and characterization of Sr_3Al_2O_6:Eu^(2+), Dy^(3+) phosphors prepared by sol-gel-combustion processing

A type of red luminescent Sr3Al2O6：Eu2＋, Dy3＋ phosphor powder is synthesised by sol-gel-combustion processing, with metal nitrates used as the source of metal ions and citric acid as a chelating agent of metal ions. By tracing the formation process of the sol-gel, it is found that it is necessary to reduce the amount of NO3 by dropping ethanol into the solution for forming a stable and homogeneous sol-gel. Thermogravimetric and Differential Scanning Calorimeter Analysis, x-ray diffractionmeter, scanning electron microscopy and photoluminescence spectroscopy are used to investigate the luminescent properties of the as-synthesised Sr3A1206：Eu2＋, Dy3＋. The results reveal that the Sr3Al2O6 crystallises completely when the combustion ash is sintered at 1250℃. The excitation and the emission spectra indicate that the excitation broadband lies mainly in a visible range and the phosphors emit a strong light at 618 nm under the excitation of 472 nm. The afterglow of （Sr0.94Eu0.03Dy0.03）3Al2O6 phosphors sintered at 1250℃ lasts for over 1000 s when the excited source is cut off.

Properties of red-emitting phosphors Sr_2MgSi_2O_7:Eu^(3+) prepared by gel-combustion method assisted by microwave

Novel red-emitting phosphors Sr2MgSi2O7：Eu3＋ were prepared by gel-combustion method assisted by microwave. The phase struc-ture and luminescent properties of as-synthesized phosphors were investigated by XRD and fluorescence spectrophotometer, respectively. The results showed that the as-synthesized sample was Sr2MgSi2O7 with tetragonal crystal structure. The excitation spectrum of Sr2MgSi2O7：Eu3＋ was composed of two major parts： one was the broad band between 200 and 350 nm, which belonged to the charge transfer of Eu3＋-O2-; the other consisted of a series of sharp lines between 350 and 450 nm, ascribed to the f-f transition of Eu3＋. The emission spec-trum consisted of two emission peaks at 593 and 616 nm, which was attributed to 5D0→7F1 and 5D0→7F2 of Eu3＋, respectively. The concen-tration of Eu3＋ （x） had great effect on the emission intensity of Sr2-xMgSi2O7：Eu3＋x. When x varied in the range of 0.04-0.18, the intensity of emission peaks at 593 and 616 nm increased gradually with the concentration of Eu3＋ increasing. It was interesting that no concentration quenching occurred. Moreover, the luminescent intensity could be greatly enhanced with incorporation of charge compensator Li＋ ions.

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.

Influences of phase composition on Sr_3SiO_5:Eu^(2+) luminous performance

a＇-Sr2SiO4：Eu2＋ phase always coexists with the Sr3SiO5：Eu2＋ phase when it is synthesized by a high-temperature solid-state method. This may affect the luminescent properties of the Sr3SiO5：Eu2＋ phosphors. We investigated the decomposition reaction of Sr3SiO5 during the cooling process with the quenching method. The results indicated that Sr3SiO5 was a stable compound above 1250℃. The Sr3SiO5 phase decomposed into a＇-Sr2SiO4 and SrO below 1250℃. The a＇-Sr2SiO4：Eu2＋ phase would coexist with the Sr3SiOs：Eu2＋ phase because of the decomposition reaction of Sr3SiO5, making the luminescent wavelength of coexistence sample move to the short-wavelength compared with the luminescent wavelength of Sr3SiO5：Eu2＋. Pure phase Sr3SiO5：Eu2＋ could be obtained by the rapid cooling method to suppress Sr3SiO5 decomposition. When the cooling rate was 20℃/min, nearly pure phase Sr3SiO5：Eu2＋ could be produced.

Preparation and Characterisation of Sr2CeO_4:Eu^(3+) Rare Earth Luminescent Material by High Temperature Mechano-Chemical Method

A novel, high-temperature, mechano-chemical（HTMC） method was developed to synthesise singlephase Sr_2CeO_4：Eu^（3＋）phosphor. Phosphors were characterised by X-ray diffraction（XRD）, scanning electron microscopy（SEM）, and luminescence spectra. Compared with phosphors prepared by the traditional hightemperature solid state method and citric acid gel method, single-phase Sr_2CeO_4：Eu^（3＋）powders by using the HTMC method, with small average particle sizes of about 5 μm, a narrow size distribution range and uniform dispersion, were prepared at 800 ℃, and reached their maximum luminescent intensity at 900 ℃.Under ultraviolet excitation at 298 nm, the sample showed good luminescence with the strongest red light of 616 nm. However, Sr_2CeO_4：Eu^（3＋）was prepared at the higher temperature of 1100 ℃ by solid state method and citric acid gel method. The particle size was too large and uneven with phosphor agglomeration by high-temperature solid state method. The luminescent intensity reached a maximum for Sr_2CeO_4：Eu^（3＋）phosphor at a synthesis temperature of 1100 ℃ by using the high-temperature solid state method, and at 1200 ℃ by both citric acid gel and chemical precipitation methods. Furthermore, the advantages of the Sr_2CeO_4：Eu^（3＋）powder prepared by HTMC method were discussed compared with that prepared using traditional high-temperature solid state and citric acid gel methods.

A novel long lasting phosphor Sr5 （PO4）3FxCll_x：Eu2＋,Gd3＋ prepared in air condition

A series of blue long afterglow mixed halide-phosphate phosphors Sr5 （PO4）3 FxCll-x：Eu2＋,Gd3＋ were synthesized in air by traditional solid-state reaction routte. The crystal structures, photoluminescence, thermolurninescenee properties and afterglow proper- ties of the phosphors were characterized systematically using X-ray diffraction （XRD）, luminescence spectrophotometer, microcom- puter thermoluminescence dosimeter and single photon counter, respectively. Under 280 nm excitation, the broadband emissions of Eu2＋ ions were observed at 445 nm （blue） due to the 4f7→4f65d transition. It was demonstrated that there existed the self-reduction of the Eu3＋ to Eu2＋ ions in this special halide-phosphate matrix in air condition. The addition of Gd3＋ ions obviously enhanced the after- glow properties of the single doped Eu2＋ ions in the halide-phosphate phosphors. And the content of the fluoride anions also had sig- nificant influence on the afterglow properties. All results indicated that Srs （PO4）3 FxCI1-x：Eu2＋,Gd3＋ might be potential phosphors for long lasting phosphorescence （LLP） materials.