Luminescence properties of YAl3(BO3)4 phosphors doped with Eu3+ ions

YAl3(BO3)4: Eu3+ phosphors were prepared by the conventional solid state reaction. The phase structure and morphology were investigated by X-ray diffraction (XRD) and scanning electron microscope (SEM). Doping YAl3(BO3)4: Eu3+ phosphors with concentration of Eu3+ ions of 0, 2, 5, 8 and 10 mol% were studied and their luminescent properties at room temperature were discussed. The excitation spectrum of Y0.95Eu0.05Al3(BO3)4 was composed of a broad band centered at about 252 nm and a group of lines in the longer wavelength re-gion. In the emission spectra, the peak wavelength was about 614 nm under a 252 nm UV excitation. The optimal doping concentration of Eu<3+ ions in YAl3(BO3)4: Eu3+ phosphors was 8 mol%.     

Luminescence properties of red phosphors Ca_（10）Li（PO_4）_7：Eu~（3＋）

A series of red phosphors Ca10Li (PO4)7:Eu3+ were synthesized by high temperature solid-state reaction method. Their luminescence properties were characterized by means of photoluminescence excitation and emission spectra,CIE chromaticity and quantum efficiency. Results indicated that the phosphors could be effectively excited by the near ultraviolet (NUV) light (393 nm). The main emission peaks of the phosphor were ascribed to the transition 5D0-7F2 (613 and 617 nm) of Eu3+ ion when samples were excited by...     

Solution combustion synthesis and luminescence properties of (Y,Gd)Al_3(BO_3)_4:Eu~(3+) phosphors

Ultrafine Y0.95-xGdxEu0.05Al3(BO3)4 phosphors with different Gd3+ concentrations were prepared by a solution combustion method, and characterized with X-ray diffraction (XRD), scanning electron microscopy (SEM). Results showed that the pure phase of YAl3(BO3)4 was obtained at 1000 oC and the prepared particle size varied with calcining temperatures. Photoluminescence spectra indicated that the dominant emission peak was observed at 612 nm due to the 5D0→7F2 transition of Eu3+. The luminescence intensity of ...     

Luminescence characteristics of Ca_4YO(BO_3)_3 doped with Bi~(3+),Dy~(3+) and Pr~(3+) ions

The photoluminescence(PL) properties of Ca4YO(BO3)3 doped with Bi3+,Dy3+,and Pr3+ ions were investigated.These compounds were prepared using a typical solid-state reaction.The excitation and emission spectra were measured using a spectrofluorometer.For Ca4YO(BO3)3:Bi3+,the excitation spectrum showed the bands at about 228,309,and 370 nm which correspond to the 1S0→1P1 transition and the 1S0→3P1 transition of Bi3+ ions.The emission band at 390 nm corresponded to the 3P1→1S0 transition of Bi3+ ions.For Ca4YO(BO3)3:Bi3+,Dy3+,energy transfer occurred from Bi3+ to Dy3+ somewhat.In Ca4YO(BO3)3:Bi3+,Dy3+,Pr3+,the excitation band at 367 nm was enhanced obviously due to the energy migration from Bi3+ to Pr3+,which converted efficiently the emission of semiconductor InGaN based light-emitting diode(LED).Therefore,the emission of Dy3+ ions was enhanced due to the energy migration from the process of Bi3+→Pr3+→Dy3+.It resulted in the good color rendering.     

Role of monovalent co-dopants on the PL emission properties of YAl_3(BO_3)_4:Ce~(3+) phosphor

The cerium(Ce3+) doped yttrium aluminium borate(YAB) phosphor was synthesized by modified solid state reaction. The phosphor's phase purity and its emission properties were studied using powder X-ray diffraction pattern and photoluminescence spectroscopy. The synthesized YAB had rhomobohedral crystal structure. The phosphor had two different excitation and emission spectra.By 325 nm excitation, the phosphor had emission at 373 nm and with 363 nm excitation; the phosphor gave violet-blue emission at 418 nm.The UV emission of the phosphor originated due to Ce3+ ions at the yttrium site and violet-blue emission owing to Ce3+ ions at non-regular sites viz., Al3+ and interstitial sites. The emission intensity of the phosphor was enhanced when monovalent ions(K+, Na+, and F–) were added as co-dopants. The crucial role of ionic radii of monovalent co-dopants on the emission enhancement of the YAB:Ce3+ phosphor was reported. Thermogravimetric study showed that the YAB possessed high thermal stability at up to 900 ℃.     

Luminescence properties of Eu~(3+):NaGd(WO_4_)2 nanoparticles and nanorods

The NaGd(WO_4)_2:Eu~(3+) phosphors were prepared by the microemulsion mediated hydrothermal method. The morphology and size of the samples could be dependent on the p H in the initial solution. These phosphors obtained had a strong absorption at 395 nm matching with the popular emission of near-UV LED chips, and could emit intense red light at 616 nm. The small ellipsoid-like particles or short rods were provided with large parameters of oscillator strength ?_2 and asymmetry ratio. Compared to the ellipsoid-like phosphors, the rod-like phosphors took on stronger emission, longer lifetime and larger quantum efficiency. This work demonstrated that the one-dimension Na Gd(WO_4)_2:Eu~(3+) phosphors might be a more favorable device than zero-dimension ones for photoluminescence.     

Luminescence properties of Eu~(3+) doped YBO_3 for temperature sensing

YBO_3:2 at.% Eu~(3+) was prepared by the solid state reaction and its temperature dependent luminescence was investigated for possible applications in temperature sensing. Phase composition of this material was confirmed by X-ray powder diffraction analysis and excitation and emission spectra were also provided. Under excitation of 355 nm, the fluorescence originating from ~5D_0 and ~5D_1 states varied as the temperature rose in a region from 333 to 773 K. The fluorescence intensity ratio(FIR) of ~5D_0 and ~5D_1 was investigated which increased significantly with the rise of temperature. The maximal relative sensitivity in the whole temperature range was 1.8% K~(–1)(at 333 K). The results recommended YBO_3:Eu~(3+) as a new material of the FIR method for non-contact optical thermometry.     

Luminescence properties of YAl3（BO3）4 phosphors doped with Eu^3＋ ions

YAl3 （BO3）4： Eu^3＋ phosphors were prepared by the conventional solid state reaction. The phase structure and morphology were investigated by X-ray diffraction （XRD） and scanning electron microscope （SEM）. Doping YAl3（BO3）4： Eu^3＋ phosphors with concentration of Eu^3＋ ions of 0, 2, 5, 8 and 10 mol% were studied and their luminescent properties at room temperature were discussed. The excitation spectrum of Y0.95Eu0.05Al3（BO3）4 was composed of a broad band centered at about 252 nm and a group of lines in the longer wavelength region. In the emission spectra, the peak wavelength was about 614 nm under a 252 nm UV excitation. The optimal doping concentration of Eu^3＋ ions in YAl3（BO3）4： Eu^3＋ phosphors was 8 mol%.     

Photoluminescence properties of nanosized strontium-yttrium borate phosphor Sr3Y2（BO3）4：Eu^3＋ obtained by the sol-gel Pechini method

Mixed strontium-yttrium borate phosphor Sr3Y2(BO3) 4 doped with Eu3+ ions was obtained by the sol-gel Pechini method.Crystal structure of the synthesized compound was analyzed by X-ray powder diffraction.Optimal conditions for the synthesis were found.Photo-physical properties of the phosphor samples were investigated by collecting excitation and luminescence spectra as well as measuring lumi-nescence lifetime.Judd-Ofelt analysis showed that Eu3+ ions occupied Y3+ sites in the crystalline network.The studied compound showed a red emission with the quantum yield of 54%-55% and can be potentially used as phosphor for plasma display panels and luminescent tubes.     

First-principles calculations and re-analysis of optical spectra and electron paramagnetic resonance parameters for Yb~(3+) in YAl_3(BO_3)_4 crystal

In this paper,the energy levels of Yb~(3+) ions in yttrium aluminum borate(YAB) crystal were calculated from a first-principles approach with an optimized defect structure obtained from the WIEN2 k package and a traditional fitting method using a more reliable computer package.The calculated results were then compared with those obtained from a re-calculation using the values of parameters given by some previous researchers.Three types of likely mistakes in the previous researcher's paper,namely over fitting,incorrect use of irreducible representation,and errors in the calculations for the EPR parameters were clearly identified and effectively rectified in this paper.The electron paramagnetic resonance(EPR) parameters,which included g factors like g(//) and g⊥ and hyperfine structure constants A// and A⊥,were also calculated through the perturbation method and compared with some observed values available in literature.There was reasonable agreement found with the experimental values which lay between the values obtained from the first-principles calculation(g//=4.000 and g⊥=1.391;A//=1032 and A⊥=360 in 10~(-4) cm~(-1) for ~(171)Yb~(3+)) and those from the fitting approach(g//=3.612 and g⊥=1.702;A//=867 and A⊥=470 in 10~(-4) cm~(-1) for ~(171)Yb~(3+)).     

Luminescent properties of Eu~(3+) doped Gd_2WO_6 and Gd_2(WO_4)_3 nanophosphors prepared via co-precipitation method

Eu3+ doped Gd2WO6 and Gd2(WO4)3 nanophosphors with different concentrations were prepared via a co-precipitation method. The structure and morphology of the nanocrystal samples were characterized by using X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM), respectively. The emission spectra and excitation spectra of samples were measured. J-O parameters and quantum efficiencies of Eu3+ 5D0 energy level were calculated, and the concentration quenching of Eu3+ luminescence in dif...     

Enhancing the performance of photovoltaic cells by using down-converting KCaGd（PO_4）_2：Eu~（3＋） phosphors

The goal of this work is aimed to improve the power conversion efficiency of single crystalline silicon-based photovoltaic (PV) cells by using the solar spectral conversion principle, which employed a down-converting phosphor to convert a high-energy ultraviolet photon to the less energetic red-emitting photons to improve the spectral response of Si solar cells. In this study, the surface of silicon solar cells was coated with a red-emitting KCaGd(PO4)2:Eu3+ phosphor by using the screen-printing technique. In addition to the investigation on the microstructure using scanning electron microscopy (SEM), we measured the short circuit current (Isc), open circuit voltage (Voc), and power conversion efficiency (η) of spectral-conversion cells and compared with those of bare solar cells as a reference. Preliminary experimental results revealed that in an optimized PV cell, an enhancement of (0.64+0.01)% (from 16.03% to 16.67%) in Δη of a Si-based PV cell was achieved.     

Dy^3＋在（LaO）3BO3和（GdO）3BO3中的光致发光

研究了Ｄｙ＾３＋在（ＬａＯ）３ＢＯ３和（ＧｄＯ）３ＢＯ３中的光致发光;探讨了基质晶体结构、稀土离子ＲＥ＾３＋的电荷半径比（Ｚ／ｒ）和Ｄｙ＾３＋含量对（Ｄｙ＾３＋）发光强度及发光颜色的影响;分析了（ＧｄＯ）３ＢＯ３中Ｂｉ＾３＋对Ｄｙ＾３＋发光的敏化作用及Ｄｙ＾３＋４Ｆ９／２→＾６Ｈ１３／２超灵敏跃迁发射的自身浓度猝灭机理。     

Luminescent properties and energy transfer mechanism from Tb~(3+) to Eu~(3+) in CaMoO_4:Tb~(3+),Eu~(3+) phosphors

A series of CaMoO_4:Tb~(3+),Eu~(3+) phosphors were prepared by the method of precipitation. The structure and morphology of the phosphors were characterized by the X-ray diffraction(XRD) and field emission scanning electron microscopy(FE-SEM). The photoluminescence properties of the prepared products were researched, and the energy transfer from Tb~(3+) to Eu~(3+) in CaMoO_4 phosphors was studied. By adjusting the doping concentration of Eu~(3+) ions in CaMoO_4:Tb~(3+),Eu~(3+) phosphors, the emitting color of the phosphors could be easily tuned from green to red. With Tb~(3+) doped in the phosphors, the red luminescence of Eu~(3+) by near UV excitation was significantly enhanced. The energy transfer efficiency, rate and average distance between Tb~(3+) and Eu~(3+) in CaMoO_4:5%Tb~(3+),x%Eu~(3+)(mole percent) phosphors(x=0.3–10) were calculated. It was found that the interaction type between Tb~(3+) and Eu~(3+) was electric dipole-dipole interaction in the phosphors.     

Luminescence thermal quenching of M_2SiO_4:Eu~(2+)(M=Sr,Ba) phosphors

In this paper,luminescence thermal quenching of M_2SiO_4:Eu~(2+)(M=Sr,Ba) orthosilicate phosphors and mechanisms for thermal quenching proposed by different authors are briefly reviewed.Depending on preparation conditions and/or Eu~(2+)-doping concentrations,the quenching temperature(T_(1/2)) and activation energy for thermal quenching of the same orthosilicate phosphor reported by different authors are inconsistent.The common conclusion is that T_(1/2) of the intermediate compound(Ba_(1-x)Sr_x)_2 SiO_4:Eu~(2+)(x≈0.5) is higher than that of either Sr_2So_4;Eu~(2+)or Ba_2SiO_4;Eu~(2+)end-member.Moreover,T_(1/2) of the best-performing SrBaSiO_4:Eu~(2+)is evidently lower than that of YAG:Ce~(3+)and some Eu~(2+)-doped nitride phosphors.Rega rding the quenching mechanism,most of the investigators attributed thermal quenching to a thermally assisted 4f-5d cross-over in the configuration coordinate diagram.Only a few authors ascribed thermal quenching to a thermally assisted photoionization of 5 d electron to conduction band of the host.Nonetheless,a close inspection of T_(1/2) and Stokes shift derived from the vibrational spectra of the intermediate compound and end-member phosphors indicates that the 5d electron photo ionization model instead of the 4f-5d crossing decay model should be the genuine mechanism for the thermal quenching of M_2 SiO_4:Eu~(2+)(M=Sr,Ba) phosphors.Since the relationship between T_(1/2) and Stokes shift of the phosphors does not support the 4 f-5 d crossing decay model.The ionization probability of the 5 d electron depends on the energy gap(E_(dC)) between 5 d_1 level of the Eu~(2+)and conduction band minimum(CBM) of the host at higher temperatures.Lattice thermal expansion would result in an elevating 5 d_1 level of the Eu~(2+)along with a diminishing CBM of the host and as a consequence a reduction in E_(dC) and an enhanced photo ionization probability at elevated temperatures.A less rigid lattice and hence a larger coefficient of thermal expansion of M_2SiO_4 hosts should be the physical origin of poorer thermal quenching properties of the orthosilicate phosphors.     

Spectroscopic properties of ytterbium doped KLu（WO_4）_2

Monoclinic Yb3+-doped KLu(WO4)2 (Yb:KLuW) crystal with large sizes was grown by top-seeded solution growth (TSSG) method. Room-temperature absorption and fluorescence spectra were measured. The ground-state energy-level splitting was 562 cm-1. The absorption cross section, peak emission cross section as well as the minimum inversion fraction ?min and the minimum absorbed pump intensity Imin were calculated. The measured emission lifetime was 0.676 ms and the emission spectral bandwidth (FWHM) was up to 55 nm. In comparison with established laser crystals the results suggested that this crystal has potential application in efficient tunable and femtosecond laser operation.     

Up-conversion luminescence from Nd~(3+) ions doped in NaBi(WO_4)_2 single crystal

The luminescence of Nd3+-doped in NaBi(WO4)2 single crystal was investigated from 10 K to room temperature.The excitation source was a pulsed dye laser in resonance into the(4G5/2+2G(1)7/2) levels of Nd3+ ions.Several blue emission bands in the up-conversion luminescence spectra corresponded to transitions from 2P1/2 to 4I9/2.Some violet bands corresponding to transitions of 4D3/2→(4I9/2,4I11/2,4I13/2) were also observed.For comparison,the luminescence spectra and decay curves excited by the pulsed 355 nm l...     

Effect of alkaline metal ions on the photoluminescence properties of Eu~(3+)-doped Ca_3Al_2O_6 phosphors

Ca_3–xAl_2O_6:x Eu~(3+)(0.02≤x≤0.10) and Ca_(2.92)Al_2O_6:0.04Eu~(3+),0.04M~+(M~+=Li~+, Na~+, and K~+) phosphors were prepared by sol-gel method and their photoluminescence properties were investigated. The crystal structure of the annealed Ca_3–xAl_2O_6:x Eu~(3+) and Ca_(2.92)Al_2O_6:0.04Eu~(3+),0.04M~+ phosphors was analyzed with X-ray diffraction(XRD). The size and morphological characteristics of the annealed phosphors were investigated with a field emission scanning electron microscope(FE-SEM). The photoluminescence properties were evaluated with a spectrofluorometer. The phosphors were effectively excited by the light of 396 nm and showed intense red emission at 616 nm, which originated from the 5D_0→7F_2 transition of Eu~(3+). Among the prepared phosphors, the Ca_(2.96)Al_2O_6:0.04Eu~(3+) phosphor showed the strongest emission intensity and the highest color purity. The addition of alkaline metal ions(Li~+, Na~+, and K~+) to Ca_(2.96)Al_2O_6:0.04Eu~(3+) phosphor degraded the emission intensity and color purity.     

Significant enhancement of blue photoluminescence intensity of Dy~(3+) modified Sr_6Ca_4(PO_4)_6F_2:Eu~(2+) phosphors

Blue-emitting phosphors Sr_6 Ca_4(PO_4)_6 F_2:Eu~(2+)(SCPF:Eu~(2+)),Sr_6 Ca_4(PO_4)_6 F_2:Eu~(2+),Dy~(3+)(SCPF:Eu~(2+),Dy~(3+))and Sr_6 Ca_4(PO_4)_6 F_2:Eu~(2+),Dy~(3+),Si~(4+)(SCPF:Eu~(2+),Dy~(3+),Si~(4+)) with apatite structure were successfully synthesized by traditional solid-state reaction under reducing atmosphere.Eu~(2+),Dy~(3+) and Si4+ions occupy the corresponding sites of Sr~(2+),Ca~(2+) and P~(5+).Strong broad blue photo luminescence band is exhibited in SCPF:Eu~(2+),Dy~(3+) phosphor ranging from 400 to 550 nm centered at 455 nm and Dy~(3+) ions are vital in creating traps.Emission intensity of Eu~(2+),Dy~(3+) co-doped SCPF:0.02 Eu~(2+),0.02 Dy~(3+) is about 1.8 times that of SCPF:0.02 Eu~(2+) and electron trap centers serve as energy transporting media.To further elucidate the formation and effect of the specific defect on the luminescence of SCPF:0.02 Eu~(2+),0.02 Dy~(3+) phosphor,the thermoluminescence properties,decay curves and thermal stability studies were performed while the Si~(4+)-P~(5+) charge compensated pho sphor SCPF:0.02 Eu~(2+),0.02 Dy~(3+),0.02 Si~(4+) was prepared as a contrast.All the results of present work indicate that Dy~(3+) co-doping can obviously enhance photoluminescence intensity of SCPF:0.02 Eu~(2+) by the electron traps generated by non-equivalence replacement of Dy~(3+)-Ca~(2+).     

Luminescence investigation of Eu~(3+)-Bi~(3+) co-doped CaMoO_4 phosphor

A series of Eu3+-Bi3+ co-doped CaMoO4 red phosphors were synthesized via the solid-sate reaction method. The crystal structures of the obtained samples were identified by X-ray powder diffraction (XRD). The photoluminescence property was investigated, and the results showed that the intensity of excitation spectra and emission spectra could be changed with different doping ratios of Bi3+/Eu3+. The proposed explanation of these changes was from the energy transfer between Bi3+ and Eu3+ and the unbalanced cha...