Synthesis and photoluminescence properties of Er3+ and Dy3+ doped Na2NbAlO5 phosphors

A series of Ln³⁺ (Ln³⁺ = Er³⁺/Dy³⁺) ions doped Na₂NbAlO₅ (NNAO) phosphors were synthesized by solid-state method. The Er³⁺ and Dy³⁺ ions doped phosphors were characterized by XRD, photoluminescence (PL) and decay profiles. The Ln³⁺-doped samples are consistent with the pure NNAO phase which is analyzed by the X-ray diffraction result. The PL graphs show that the intensity of luminescence increases with the increasing doping concentrations up to their critical certain values and then decreases at higher concentrations due to the concentration quenching effect of Er³⁺/Dy³⁺ ions. The energy level diagrams containing the positions of 4f and 5d energy levels of Er³⁺ and Dy³⁺ ions have been established and studied. In addition, under the ultraviolet light, the prepared NNAO:xLn³⁺ (Ln³⁺ = Er³⁺/Dy³⁺) phosphors show the characteristic green (Er³⁺), cyan (Dy³⁺) emission, respectively. Under the excitation of 365 nm, the quantum efficiencies of NNAO:0.01Er³⁺ and NNAO:0.03Dy³⁺ phosphors are measured to be 61.7% and 72.2%, respectively. The obtained results indicate that the new NNAO:xLn³⁺ (Ln³⁺ = Er³⁺/Dy³⁺) phosphors are promising applications in white-light emitting diodes field.     

A single-phase full-color phosphor Sr2Ca2La(PO4)3O:Eu2+,Tb3+,Mn2+: Photoluminescence and energy transfer

A single-phase full-color emitting phosphor Sr₂Ca₂La(PO₄)₃O:Eu²⁺,Tb³⁺,Mn²⁺ was synthesized by the high temperature solid-state method. The phase formation, luminescence properties, thermal stability, and energy transfer from Eu²⁺ to Tb³⁺ and Eu²⁺ to Mn²⁺ in Sr₂Ca₂La(PO₄)₃O were investigated in details. Tunable emission color from blue to blueish green or orange can be observed under 365 nm near-ultraviolet excitation based on the energy transfer from Eu²⁺ to Tb³⁺ or Mn²⁺ ions by varying the ratio of Eu²⁺/Tb³⁺ or Eu²⁺/Mn²⁺ ions. White light was obtained with chromaticity coordinates of (0.3558, 0.3500) in the Sr₂Ca₂La(PO₄)₃O:0.04Eu²⁺,0.08Tb³⁺,0.40Mn²⁺ phosphor, suggesting their potential applications in white light emitting diodes.     

Single-phase white-emitting and tunable color phosphor Na3Sc2(PO4)3:Eu2+,Dy3+: Synthesis,luminescence and energy transfer

A series of Eu²⁺/Dy³⁺ single doped and co-doped Na₃Sc₂(PO₄)₃ phosphors were synthesized by the high-temperature solid-state method, and their phase, morphology, and luminescence properties were characterized. Under the excitation of 370 nm, the Na₃Sc₂(PO₄)₃:Eu²⁺,Dy³⁺ phosphor can emit white light whose spectrum is composed of a broad emission band centered at 460 nm and the other three peaks at 483, 577, and 672 nm, respectively. There is energy transfer from Eu²⁺ to Dy³⁺ ion in Na₃Sc₂(PO₄)₃:Eu²⁺,Dy³⁺ phosphor due to the good overlap between the emission spectrum of Na₃Sc₂(PO₄)₃:Eu²⁺ and the excitation spectrum of Na₃Sc₂(PO₄)₃:Dy³⁺, which is further confirmed by the fluorescence lifetime decrease of Eu²⁺ ion with the increase of Dy³⁺ concentration. The process of energy transfer is via dipole–quadruple interaction which is confirmed by applying Dexter's theory. By increasing the Dy³⁺ concentration, the color coordinates of the Na₃Sc₂(PO₄)₃:0.01Eu²⁺,xDy³⁺ phosphors can be adjusted from blue to white, and then to yellow. The optimized concentration of Dy³⁺ ions is 4.0 mol%, beyond which the concentration quenching will take place. The Na₃Sc₂(PO₄)₃:Eu²⁺,Dy³⁺ phosphor shows fairly good resistance to thermal quenching behavior, of which the emission intensity at 423 K can maintain 90.3% of the initial value (298 K). These results suggest that the Na₃Sc₂(PO₄)₃:0.01Eu²⁺,xDy³⁺ phosphors have potential applications as the color-tunable or a single-phase white emitting phosphor in white LEDs.     

Synthesis and optical characterization of Eu2+,Tb3+-codoped Sr3Y(PO4)3 green phosphors

A series of Eu~(2+),Tb~(3+)-codoped Sr_3 Y(PO_4)_3(SYP) green phosphors were synthesized by hightemperature solid-state reaction. Several techniques, such as X-ray diffraction, UV-vis spectrum,and photoluminescence spectrum, were used to investigate the obtained phosphors. The present study investigates in detail photoluminescence excitation and emission properties, energy transfer between the two dopants, and effects of doping ions on optical band gap. SYP:0.05 Eu2+ phosphor shows an intense and broad excitation band ranging from 220 to 400 nm and exhibits a bright green emission band with CIE chromaticity coordinates(0.189, 0.359) under 350 nm excitation. Green emission of SYP:0.03 Tb3+ is intensified by codoping with Eu~(2+), and energy transfer mechanism between them is demonstrated to be a dipole-dipole interaction. Upon 350 nm excitation, SYP:Eu~(2+),Tb~(3+) phosphors exhibits two dominating bands peaking at 466 and 545 nm, which are assigned to 4 f~65 d~1→4 f~7 transition of Eu~(2+) ions and ~5 D_4→~7 F_5 transition of Tb~(3+) ions, respectively. Optimal doping concentrations of Eu~(2+) and Tb~(3+) in the SYP host are 5 mol% and 15 mol%, respectively. Results indicate that SYP:Eu~(2+),Tb~(3+) phosphors are potentially used as green-emitting phosphors for white light-emitting diodes.     

White-light emitting single-phase phosphor La3Si6N11:Dy3+,Tb3+: Color tunable emission,thermal stability and energy transfer process

A novel white-light emitting single-phase phosphor La₃Si₆N₁₁:Dy³⁺, exhibiting two emission peaks centering at 475 and 575 nm, was prepared via conventional solid-state reactions. The structure and morphology of La₃Si₆N₁₁:Dy³⁺/Tb³⁺ were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The emission colors can be tuned from white to yellow-green through increasing the Tb³⁺ concentration in La₃Si₆N₁₁:Dy³⁺,Tb³⁺. The mechanism of energy transfer (ET) from Dy³⁺ to Tb³⁺ is confirmed according to the excitation, emission spectra and decay lifetimes curve. The temperature-dependent luminescence measurements of La_2.83Si₆N₁₁:0.1Dy³⁺,0.07Tb³⁺ were also performed, and a good thermal stability is shown, suggesting superior properties for the application as white light-emitting diodes (w-LEDs) phosphor.     

Broadband near-infrared luminescence and energy transfer of Cr~(3+),Ce~(3+) co-doped Ca_2LuHf_2Al_3O_(12) phosphors

Broadband near-infrared phosphors are highly desirable for food testing.Targeted Ca₂LuHf₂Al₃O₁₂:Cr³⁺(CLHA:Cr³⁺) and Ca₂LuHf₂Al₃O₁₂:Ce³⁺,Cr³⁺(CLHA:Ce³⁺,Cr^(³⁺)) phosphors were synthesized by the conventional high-temperature solid state reaction.The CLHA:Cr³⁺phosphor,with a good thermal stability,shows a red shift owing to radiation reabsorption and non-radiative transition with increasing Cr³⁺content.For co-doped sample,the emission intensity of Cr³⁺can be enhanced by three times due to the energy transfer from Ce³⁺to Cr³⁺,which can be evidenced by a significant overlap between the PLE of Cr³⁺single-doped phosphor and the PL of Ce³⁺single-doped phosphor.In addition,the mechanism of energy transfer is identified as a quadrupole-quadrupole interaction according to decay Lifetime and Dexter’s energy transfer formula.The broadband NIR emission peaked at 775 nm of CLHA:Cr³⁺,Ce³⁺phosphor shows a bright prospect in nondestructive quality-control analysis systems for food.     

Tunable emission,energy transfer and thermal stability of Ce3+, Tb3+ co-doped Na2BaCa(PO4)2 phosphors

A series of single Ce³⁺ doped and Ce³⁺ and Tb³⁺ co-doped Na₂BaCa(PO₄)₂ (NBCP) phosphors was synthesized by conventional solid-stated reaction method. The crystal structure, luminescence properties, thermal stability and energy transfer were carefully investigated. Ce³⁺ is inferred to substitute the Ba²⁺ site in NBCP lattice. The color-tunable emission from blue to green is observed by adjusting Tb³⁺ concentration among NBCP:0.03Ce³⁺,yTb³⁺ phosphors. The energy transfer behavior from Ce³⁺ to Tb³⁺ ions is both illustrated by co-doped PL spectra and decay curves. The energy transfer efficiency is as high as 91.5%. The mechanism of energy transfer is resonance type of dipole-dipole transition. In this work, the optimal phosphor exhibits the excellent thermal stability which keeps at 94.9% of that initial value at room temperature when temperature reaches to 150 °C. The Ce³⁺ and Tb³⁺ co-doped NBCP phosphor is a promising candidate for the application in the general lighting and display fields.     

Effect of Eu3+ doping on luminescence properties of a KAlSiO4:Sm3+ phosphor

This study presents the photoluminescence characteristic analysis of a series of red phosphors of KAlSiO₄:1.5 mol%Sm³⁺,x mol%Eu³⁺ (x = 2, 3, 4, 5, 6, 7) prepared via high-temperature solid-phase reaction. The results show that the X-ray diffraction (XRD) refinement results are reliable. The unit cell parameters and volume gradually decrease as the Eu³⁺ concentration increases, resulting in a grain size reduction of 10.22%. When x = 6, the emission peaks of Sm³⁺ at 564, 601, and 651 nm disappear completely, and the corresponding full width at half maximum becomes 0. At 610 nm, the emission peak intensity of Eu³⁺ is increased by a factor of 4.8. The resonant non-radiative energy transfer effect is greater than the co-excitation effect. A maximum energy transfer efficiency of 97.8% is achieved. The integral area at 610 nm is as high as 85%. The color purity of the phosphor is as high as 92.97%, and the internal quantum yield gradually changes from 32% to 51%. Ultimately, these results confirm that the silicate phosphor is suitable for the red component in the three primary color phosphors of white light-emitting diodes.     

Tunable luminescence in co-doped Zn3Al2Ge2O10:Cr3+ by controlling crystal field splitting and nephelauxetic effect

Ce³⁺/Dy³⁺/Tb³⁺/Eu³⁺/Mn²⁺and Cr³⁺ ions co-doped Zn₃ Al₂ Ge₂ O₁₀ phosphor were prepared by a hightemperature solid-state method.X-ray diffraction patterns prove the cubic phase structure of prepared Zn₃ Al₂ Ge2 O₁₀ phosphor,Emission,excitation spectra and decay curves confirm the tunable luminescence.Different degrees of the decrease of emission FWHM in Zn<...     

An optical thermometer with high sensitivity and superior signal discriminability based on dual-emitting Ce3+/Eu2+ co-doped La5Si2BO13 thermochromic phosphor

A novel non-contact optical thermometer, qualified with high sensitivity and temperature resolution, is urgently needed for temperature measuring of micro devices, moving objects and specific severe environments. Hence, a series of dual-emitting La₅Si₂BO₁₃:Ce³⁺,Eu²⁺ phosphors were synthesized. The two ions show diverse responses with the changing in temperature. The variational emissions of Ce³⁺ and Eu²⁺ can be converted to FIR (fluorescence intensity ratio) signals. The maximal absolute sensitivity S_a and relative sensitivity S_r reach up to 0.07526%/K and 3.2241%/K, respectively. It is worthy noting that the S_a and S_r possess the same variation tendency and both have high values in the low temperature region (293–373 K), showing the great temperature measuring property especially in low temperature region. The temperature sensing characteristics are superior to the results of most previous reports. The energy transfer (ET) process is certified to occur from Ce³⁺ to Eu²⁺ ions. These studies indicate that La₅Si₂BO₁₃: Ce³⁺,Eu²⁺ phosphor could have a good prospect for optical thermometry.     

Tunable luminescence,energy transfer and excellent thermal stability of SrMg_2(PO_4)_2:Ce~(3+),Tb~(3+) phosphors for LEDs

A series of novel SrMg_2(PO_4)_2:Ce~(3+),Tb~(3+)(SMP:Ce~(3+),Tb~(3+)) phosphors with tunable emission spectra were produced via high temperature solid phase method.XRD,fluorescence spectrum and fluorescence lifetime for SMP:Ce~(3+),Tb~(3+)were studied in detail.Under the excitation at 308 nm,SMP:Ce~(3+),Tb~(3+) samples can emit high efficiency tunable blue-green light by controlling the proportion of dopant concentration.Through the spectral overlap and the regular change of fluorescence lifetime,it is proved that there is a significant energy transfer between Ce~(3+) and Tb~(3+) in SMP matrix and the energy transfer mechanism is determined to be an electric dipole-dipole interaction with energy transmission efficiency of 55%.In additional,Commission International de L'Eclairage(CIE) color coordinates and thermal stability were studied.All above findings suggest that SMP:Ce~(3+),Tb~(3+)can be regarded as the potential bluish green phosphor for LED applications.     

Preparation and luminescence properties of orange-red Ba3Y4O9:Sm3+ phosphors

A novel orange-red emitting Ba₃Y₄O₉:Sm³⁺ phosphors were prepared by a high temperature solid-state reaction in air. X-ray diffraction (XRD), photoluminescence spectra, fluorescence decay and temperature-dependent emission spectra were utilized to characterize the structure and luminescence properties. The results show that the excitation spectrum includes a series of linear peaks at 350, 367, 382, 410, 424, 445, 470 and 495 nm, respectively. Under 410 nm excitation, the emission peaks were located at 574 nm (⁴G_5/2—⁶H_5/2), 608 nm (⁴G_5/2—⁶H_7/2), 659 nm (⁴G_5/2—⁶H_9/2) and 722 nm (⁴G_5/2—⁶H_11/2), respectively. The concentration quenching occurs when x equals 0.08 for Ba₃Y_4–xO₉:xSm³⁺ phosphor and its mechanism is ascribed to the dipole–dipole interaction. The chromaticity coordinates of Ba₃Y_3.92O₉:0.08Sm³⁺ phosphor are in the orange-red region. The temperature-dependent study shows that this phosphor has excellent luminescence thermal-stability. And the luminescence intensity of Ba₃Y_3.92O₉:0.08Sm³⁺ phosphor at 473 K only declines by about 25.75% of its initial intensity. The experimental data indicate that Ba₃Y₄O₉:Sm³⁺ phosphor may be promising as an orange-red emitting phosphor for white light emitting diodes.     

Tunable luminescence and energy transfer in Y_2BaAl_4SiO_(12):Tb~(3+),Eu~(3+)phosphors for solid-state lighting

Single-phase Y₂BaAl₄SiO₁₂:Tb³⁺,Eu³⁺phosphors with adjustable luminescence were successfully prepared by high-temperature solid-state reaction method.The structural,luminescent properties and ene rgy transfer(ET) process of Y₂BaAl₄SiO₁₂:Tb^(³⁺),Eu³⁺phosphors were syste matically analyzed with the help of X-ray diffraction(XRD),scanning electron microscopy(SEM),excitation spectra,emission spectra and photoluminescence decay curves.Tunable luminescence ranging from green through yellow and definitively to red can be achieved by elevating amounts of Eu³⁺ions in Tb³⁺,Eu³⁺co-doped samples.Besides,the ET mechanism and efficiency were also analyzed and the maximum ET efficiency is 67%.All the results show that Y₂BaAl₄SiO₁₂:Tb³⁺,Eu³⁺phosphors can be used in solid-state lighting.     

Preparation of Eu2+, Dy3+, Zr4+ ions co-doped strontium aluminate/molybdate multi-optical functional hybrid pigments for anti-counterfeiting

Eu²⁺,Dy³⁺ and Zr⁴⁺ ions co-doped strontium aluminate(i.e.,SrAl₂O₄:Eu²⁺,Dy³⁺,Zr⁴⁺)/molybdate(i.e.,Ho₂MoO₆ or Nd₂MoO₆) with photo-/mechano-luminescence and allochroic effect as multi-optical functional hybrid pigments were prepared via solid state reactions and subsequent mixing.The phosphor and hybrid pigments were characterized by X-ray diffraction,scanning electron...     

Luminescent and thermometric properties of dual emitting Eu~(2+)/Sm~(3+) co-doped Sr_4La(PO_4)_3O phosphor based on energy transfer

Eu²⁺/Sm³⁺co-doped dual-emitting Sr₄La(PO₄)₃O phosphors were synthesized through a convenient high temperature solid state reaction in reductive atmosphere.The structure,luminescence,energy transfer and temperature-dependent luminescence properties of Eu²⁺/Sm³⁺co-doped Sr₄La(PO₄)₃O phosphors were researched and analyzed in detail.The blue emission of Eu²⁺and the red emission of Sm³⁺can work together as FIR signals.Based on the different response characteristics of these two ion emissions to temperature,Sr₄La(PO₄)₃O:Eu²⁺/Sm^(³⁺)phosphor achieves the relative sensitivity of0.48384%/K and a wide range of temperature measurements from room temperature to 573 K.The results reveal that the Sr₄La(PO₄)₃O:Eu²⁺/Sm³⁺phosphor has application prospect in the field of high temperature optical thermometry.The energy transfer mechanism is proved to be the dipole-dipole interaction between Eu²⁺and Sm³⁺ions.     

Fine controllable blue emission and its mechanism in Ce3+-doped orthosilicate solid solution phosphors for different plant growths

The designed Ce~(3+)-doped alkaline-earth silicate phosphors Ca_mSr_(2-m-n)Ba_nSiO_4:Ce~(3+),Li~+(CSBS:Ce~(3+))were synthesized by a high temperature solid-state reaction. The crystal field splitting and the centroid shift from the free ion energy of 5 d configuration were approximated from the spectrum for Ca_2SiO_4,Sr_2SiO_4 and Ba_2SiO_4 phosphors. The single-phase purity was checked by means of X-ray diffraction. Here,when the doped concentration of Ca~(2+) is less than 80%(m ≤1.6), we report the structural phase transformation from monoclinic system β-Ca_2SiO_4 to orthorhombic system α-Ca_2SiO_4. The phosphors excited by near-ultraviolet(NUV) light at wavelengths ranging from 200 to 400 nm demonstrate a broad asymmetric blue emission band. The emission peak wavelength redshifts firstly from 417 nm of Ca_2SiO_4 to 438 nm of Sr_(0.3)Ca_(1.6)SiO_4, and then blueshifts to 411 nm of Sr_2SiO_4, and the end of 401 nm of Ba_2SiO_4.These results indicate that the tunable blue-emission of the phosphors can be realized through changing the solid solution components, which has a potential use as a blue component for fabricated precision modulation LEDs light sources and auxiliaries of SSC plastics films for different plant growths.We discuss in detail the possible mechanism and energy diagram of the tunable blue luminescence in Ca_mSr_(2-m-n)Ba_nSiO_4:Ce~(3+),Li~+ phosphors.     

Luminescent ionic lattice occupation and wide tunable emission spectra of La2MgZrO6:Bi3+,Eu3+ double perovskite phosphors for white light LED

La₂Mg_1-x/2Zr_1-x/2O₆:xBi³⁺(x=0.01-0.035,abbreviated as LMZ:Bi³⁺) and La_2-yMg_0.99Zr_0.99O₆:0.02Bi³⁺,yEu³⁺(y=0.1-0.11,abbreviated as LMZ:Bi³⁺,Eu³⁺) double-perovskite phosphors were prepared through high-temperature solid-phase method.The emission spectrum of LMZ:xBi³⁺(x=0.01-0.035)phosphors excited at 353 nm is asymmetric in the range be...     

Synthesis,structure and optical properties of novel thermally robust Dy~(3+)-doped Ca_9Sc(PO_4)_7 phosphors for NUV-excited white LEDs

The powder samples of Ca₉Sc(PO₄)₇:xDy^{^(3+})white emitting phosphors were prepared via a solid state reaction technique.The Ca₉Sc(PO₄)₇:Dy³⁺samples were researched by using the GSAS Rietveld refinement and X-ray diffraction(XRD) methods,and SEM images and elemental maps were recorded.Under 350 nm excitatio n,the emission spectra of Ca₉Sc(PO₄)₇:xDy³⁺samples have two obvious peaks and one weak peak at 484,572 and660 nm,corresponding to the characteristic electron transitions of(⁴F_9/2→ ⁶H_15/2,blue),(⁴F_9/2→ ⁶H_13/2,yellow) and(⁴F_9/2→ 6 H11/2,red),respectively.The concentration quenching effect,decay lifetime and thermal quenching of the as-synthesized Ca₉Sc(PO₄)₇:Dy³⁺samples were researched systematically.The Ca₉Sc(PO₄)₇:0.02 Dy³⁺phosphor possesses a good thermal stability,of which the emission intensity at 423 K can maintain 79% of the initial value(273 K).In addition,through the study of the chro maticity coordinates of the Ca₉Sc(PO₄)₇:0.02 Dy³⁺phosphor,it is found that it is located in the white region,and the Commission Internationalede L’Eclairage(CIE) chromaticity coordinates are(0.339,0.389),The above results show that Ca₉Sc(PO₄)₇:xDy³⁺phosphors can be excellent candidate material for applications in NUV-excited white LEDs.     

Optical and luminescence characteristics of Eu3+-doped B2O3:SiO2:Y2O3:CaO glasses for visible red laser and scintillation material applications

Europium(Eu~(3+)) doped glasses of chemical compositions(55-x)B_2O_3:10 SiO_2:25 Y_2O_3:10CaO:xEu_2O_3,where x denotes mol% and ranges 0≤ x ≤ 2.5, were synthesized by adopting conventional melt quenching technique, Physical properties like density, molar volume, polaron radius, inter-ionic distance and field strength of the glass samples were investigated to assess the impact of Eu_2O_3. Optical and luminescence properties of the glasses were characterized with optical absorption, photoluminescence,X-ray induced emission spectra, temperature dependence emission spectra and decay times. Judd-Ofelt(JO) intensity parameters(Ω_λ) of the glasses were evaluated based on the absorption spectrum of 0.5 mol%. JO parameters, calculated from absorption spectra with thermal corrections on oscillator strength, were used to evaluate radiative properties such as radiative transition probability(A_R),branching ratio(β_R), stimulated cross section emission(σ) and radiative lifetime(τ_R) for ~5D_0→~7 F_J(J = 0,1,2,3 and 4) transitions. The decay rate of ~5D_0 fluorescent level for all the glass samples was single exponential. Lifetimes of the ~5D_0 level were decreased with increasing concentrations of Eu~(3+)ions from 0.05 mol% to 2.5 mol% which might be due to energy transfer through cross-relaxation in the glasses. The chromaticity coordinates(x, y) were similar for all BSYCaEu glasses and were located at the red region of CIE 1931 color chromaticity diagram. Hence, these results confirm that the Eu~(3+) doped BSYCaEu glasses could be useful for visible red lasers and glass scintillation applications.     

Thermally stable photoluminescence and long persistent luminescence of Ca3Ga4O9:Tb3+/Zn2+

A green long persistent luminescence (LPL) phosphor Ca₃Ga₄O₉:Tb³⁺/Zn²⁺ was prepared. Ca₃Ga₄O₉ matrix exhibits blue self-activated LPL due to the creation of intrinsic traps. When Tb³⁺ is doped, the photoluminescence (PL) and LPL colors change from blue to green with their intensities significantly enhanced. The doping of Zn²⁺ evidently improves the PL and LPL performances of the Ca₃Ga₄O₉ matrix and Ca₃Ga₄O₉:Tb³⁺. The thermoluminescence (TL) spectra show that a successive trap distribution is formed by multiple intrinsic traps with different depths in the Ca₃Ga₄O₉ matrix, and the incorporation of Tb³⁺ and Zn²⁺ effectively increases the densities of these intrinsic traps. The existence of a successive trap distribution makes the Ca₃Ga₄O₉:Tb³⁺/Zn²⁺ phosphor exhibit thermally stable PL and LPL. It is indicated that this phosphor shows great promise for the application such as high-temperature LPL phosphor.