Photoluminescence and electron-beam excitation induced cathodoluminescence properties of novel green-emitting Ba4La6O(SiO4)6:Tb3+phosphors

Tb³⁺ions activated Ba₄La₆O(SiO₄)₆ (BLSO:Tb³⁺) phosphors were synthesized by a citrate sol-gel method. The X-ray diffraction pattern confirmed their oxyapatite structure. The field-emission scanning electron microscope image established that the BLSO:Tb³⁺phosphor particles were closely-packed and acquired irregular shapes. The photoluminescence (PL) excitation spectra of BLSO:Tb³⁺phosphors showed intense f–d transitions along with low intense peaks corresponding to the f–f transitions of Tb³⁺ions in the lower energy region. The PL emission spectra displayed the characteristic emission bands of Tb³⁺ions, and the optimized concentrations were found to be at 1 and 6 mol% for blue and green emission peaks, respectively. The cathodoluminescece (CL) spectra exhibited a similar behavior that was observed in the PL spectra except the intensity variations in the blue and green regions. The CL spectra of the BLSO:6 mol% Tb³⁺phosphor unveiled accelerating voltage induced luminescent properties.     

Novel efficient SrMgY3(SiO4)3F:Ce3+,Tb3+ phosphor with tunable color and thermal stability through energy transfer

A novel apatite-type SrMgY₃(SiO₄)₃F was synthesized by a high-temperature solid-state reaction. The crystal structure was refined using powder X-ray diffraction data. SrMgY₃(SiO₄)₃F crystallizes in P6₃/m hexagonal space group with lattice parameters of a = b = 9.45270 Å, c = 6.77617 Å, and V = 524.357 Å³. The incorporation of the Ce³⁺ and Tb³⁺ ions into the matrix can generate bright blue and green lights under ultraviolet (UV) light excitation. The codoped Ce³⁺ and Tb³⁺ in SrMgY₃(SiO₄)₃F can effectively improve green emission intensity and thermal stability through the energy transfer from the Ce³⁺ to Tb³⁺ ions. With the increase of Tb³⁺-doping content, the luminescent color of phosphor changes from blue to cyan and finally to green. SrMgY₃(SiO₄)₃F:0.06Ce³⁺,0.90Tb³⁺ phosphor exhibited intense green light emission with a quantum yield of 59.49% and good thermal stability, with an emission intensity at 150°C was 96% of that at 30°C. Finally, the prepared sample was coated on 365 nm UV chips to fabricate white light-emitting diodes with a color rendering index of 82.6 and a correlated color temperature of 2912 K, demonstrating its potential for applications in display and lighting.     

Multicolour tunable luminescence of thermal-stable Ce3+/Tb3+/Eu3+-triactivated Ca3Gd(GaO)3(BO3)4 phosphors via Ce3+ → Tb3+ → Eu3+ energy transfer for near-UV WLEDs applications

A series of single-component blue, green and red phosphors have been fabricated based on the Ca₃Gd(GaO)₃(BO₃)₄ host through doping of the Ce³⁺/Tb³⁺/Eu³⁺ ions, and their crystal structure and photoluminescence properties have been discussed in detail. A terbium bridge model via Ce³⁺ → Tb³⁺ → Eu³⁺ energy transfer has been studied. The emission colours of the phosphors can be tuned from blue (0.1661, 0.0686) to green (0.3263, 0.4791) and eventually to red (0.5284, 0.4040) under a single 344 nm UV excitation as the result of the Ce³⁺ → Tb³⁺ → Eu³⁺ energy transfer. The energy transfer mechanisms of Ce³⁺ → Tb³⁺ and Tb³⁺ → Eu³⁺ were found to be dipole-dipole interactions. Importantly, Ca₃Gd(GaO)₃(BO₃)_4:Ce³⁺,Tb³⁺,Eu³⁺ phosphors had high internal quantum efficiency. Moreover, the study on the temperature-dependent emission spectra revealed that the Ca₃Gd(GaO)₃(BO₃)_4:Ce³⁺,Tb³⁺,Eu³⁺ phosphors possessed good thermal stability. The above results indicate that the phosphors can be applied into white light-emitting diodes as single-component multi-colour phosphors.     

Tunable Emission Phosphor Ca4Y6O(SiO4)6:Ce3+, Eu2+: Luminescence and Energy Transfer

A series of Ca_4–yY_6–xO(SiO₄)₆: xCe³⁺, yEu²⁺ samples are synthesized by a high‐temperature solid‐state method. Under 356 nm excitation, Ca₄Y₆O(SiO₄)₆:Ce³⁺ presents a strong blue emission band at 426 nm which are assigned to 4f⁰5d¹→4f¹ transition of Ce³⁺ ion. Ca₄Y₆O(SiO₄)₆:Eu²⁺ shows green emission under 380 nm radiation excitation, and the peak locates at 527 nm which is mainly due to transitions of Eu²⁺ from 4f⁷ ground state to 4f⁶5d¹ excited state. Under 356 nm excitation, a remarkable energy transfer from Ce³⁺ to Eu²⁺ exists in Ca₄Y₆O(SiO₄)₆, and the result reveals that the mechanism of energy transfer is a resonant type via a nonradiative dipole–dipole interaction. The hues of Ca₄Y₆O(SiO₄)₆:Ce³⁺, Eu²⁺ can be adjusted by the energy transfer from Ce³⁺ to Eu²⁺ ions, and a white emission can be achieved by tuning the ratio of Ce³⁺ to Eu²⁺. The results mean that Ce³⁺ may be the effective sensitizer for Eu²⁺‐doped Ca₄Y₆O(SiO₄)₆.     

New apatite-type phosphor Ca9La(PO4)5(SiO4)F2:Tb3+,Dy3+ with improved color rendering index

Ca₉La(PO₄)₅(SiO₄)F₂:Tb³⁺,Dy³⁺ (CLPSF:Tb³⁺,Dy³⁺) phosphors were successfully prepared using the traditional solid-state technique. The crystal structure was refined and the luminescence properties have been examined in detail. The band gap and electronic structure of Ca₉La(PO₄)₅(SiO₄)F₂ were performed by the periodic density functional theory (DFT) calculation. The spectral and fluorescence decay dynamics of CLPSF:Tb³⁺,Dy³⁺ show that the energy transfer behavior between Tb³⁺ and Dy³⁺ ions is observed. The CLPSF:Tb³⁺,Dy³⁺ phosphors can be efficiently excitable at the wavelengths range from 300 to 500 nm. The emission spectrum covers the whole visible part of the spectra with the sharp emission bands in red, green, and blue regions. The correlated color temperature (CCT) and color rendering index (CRI) of white light emission could be improved by the fine-tuning of the Tb³⁺ and Dy³⁺ ions ration in accordance with the energy transfer behavior. Thus, the CLPSF:Tb³⁺,Dy³⁺ phosphor could be used as a material for the near-ultraviolet (n-UV) and white light-emitting diodes (w-LEDs).     

Novel Emitting‐Color Tunable Phosphors Ba3Y2(BO3)4:Ce3+,Tb3+ with Efficient Energy Transfer for Near‐UV Light‐Emitting Diodes

This work presents the ultraviolet–visible spectroscopic properties of Ba₃Y₂(BO₃)₄:Ce³⁺,Tb³⁺ phosphors prepared by a high‐temperature solid‐state reaction. Under ultraviolet light excitation, tunable emission from the blue to yellowish‐green region was obtained by changing the doping concentration of Tb³⁺ when the content of Ce³⁺ is fixed. The efficient energy transfer process between Ce³⁺ and Tb³⁺ ions was observed and confirmed in terms of corresponding excitation and emission spectra. In addition, the energy transfer mechanism between Ce³⁺ and Tb³⁺ was proved to be dipole–dipole interaction in Ba₃Y₂(BO₃)₄:Ce³⁺,Tb³⁺ phosphor. By utilizing the principle of energy transfer and appropriate tuning of Ce³⁺/Tb³⁺ contents, Ba₃Y(BO₃)₄:Ce³⁺,Tb³⁺ phosphors can have potential application as an UV‐convertible phosphor for near‐UV excited white light‐emitting diodes.     

Luminescence Properties and Energy Transfer of Ce3+,Tb3+‐Coactivatedβ‐SiAlON Phosphors

Using the solid‐state reaction method, Ce³⁺,Tb³⁺‐coactivated Si₅AlON₇ (Si_6?zAl_zO_zN_8?z, z = 1) phosphors were successfully synthesized. The obtained phosphors exhibit high absorption and strong excitation bands in the wavelength range of 240–440 nm, matching well with the light emitting‐diode (LED) chip. The ET from Ce³⁺ to Tb³⁺ ions in Si₅AlON₇:Ce³⁺,Tb³⁺ has been studied and demonstrated by the luminescence spectra and decay curves. Moreover, the phosphors show tunable emissions from blue to green by tuning the relative ratio of the Ce³⁺ to Tb³⁺ ions. Thermal quenching properties of Si₅AlON₇:Ce³⁺,Tb³⁺ had also been investigated and the quenching temperature is ~190°C. These results show that Si₅AlON₇:Ce³⁺,Tb³⁺ could be a promising candidate for a single‐phased color‐tunable phosphor applied in UV‐chip pumped LEDs.     

Ce3+/Tb3+-coactived NaMgBO3 phosphors toward versatile applications in white LED,FED, and optical anti-counterfeiting

Ce³⁺/Tb³⁺ co-doped NaMgBO₃ phosphors were successfully synthesized by solid-state method. Under 381 nm excitation, the cyan emission owing to the 5d → 4f of Ce³⁺ ions and green emissions arising from the ⁵D₄ → ⁷F_J (J = 6, 5, 4, and 3) transitions of Tb³⁺ ions were seen in all the phosphors. Through theoretical analysis, one knows that the energy transfer from Ce³⁺ to Tb³⁺ ions with high efficiency of 83.74% was contributed by dipole–dipole transition. Furthermore, the internal quantum efficiency of NaMgBO₃:0.01Ce³⁺,0.03Tb³⁺ phosphor was 54.28%. Compared with that of at 303 K, the emission intensity of the developed products at 423 K still kept 73%, revealing the splendid thermal stability of the studied phosphors. Through utilizing the resultant phosphors as cyan-green components, the fabricated white-LED device exhibited an excellent correlated color temperature of 2785 K, high color-rendering index of 85.73, suitable luminance efficiency of 25.00 lm/W, and appropriate color coordinate of (0.4279, 0.3617). Aside from the superior photoluminescence, the synthesized phosphors also exhibited excellent cathode-luminescence properties which were sensitive to the current and accelerating voltage. Furthermore, the NaMgBO₃:0.01Ce³⁺,0.03Tb³⁺ phosphors with multi-mode emissions were promising candidates for optical anti-counterfeiting. All the results indicated that the Ce³⁺/Tb³⁺ co-doped NaMgBO₃ phosphors were potential multi-platforms toward white-LED, field emission displays, and optical anti-counterfeiting applications.     

Structure and Photoluminescence of A Blue‐Green‐Emitting Phosphor for Near‐UV White LEDs

A series of phosphors Ca_12(0.97?x)Al₁₄O₃₂F₂: 0.03Ce³⁺, xTb³⁺ have been prepared by a hightemperature solid‐state reaction using boric acid as flux. These oxyfluorides crystallize in cubic structure, space group. Under the near ultraviolet excitation within wavelength range 310–390 nm, Ca_12(0.97?x)Al₁₄O₃₂F₂: 0.03Ce³⁺, xTb³⁺ phosphors exhibit an intense emission covering a broad band of 370–500 nm derived from the 5d→4f transitions of Ce³⁺ and a characteristic emission at 544 nm of Tb³⁺. The emission can be tuned from blue to green by altering the relative ratio of Ce³⁺ to Tb³⁺ in the composition. The energy‐transfer mechanism from Ce³⁺ to Tb³⁺ is investigated based on the site occupancy of the luminescence center in the crystal structure of the Ca₁₂Al₁₄O₃₂F₂ host. More importantly, when a certain amount of boric acid is added as flux in the synthesis, the fluorescence intensity of the phosphors increases about 65%. Because of its broad excitation and efficiently tunable blue to green luminescence, the Ca_12(0.97?x)Al₁₄O₃₂F₂: 0.03Ce³⁺, xTb³⁺ phosphors may find promising application as a near UV‐convertible phosphor for white‐light‐emitting diodes.     

Luminescence properties and energy transfer of GdAl3(BO3)4:Ce3+, Tb3+ phosphor

Ce³⁺ and Tb³⁺ singly doped and co-doped GdAl₃(BO₃)₄ phosphors were synthesized by solid state reaction. The crystal structure, the luminescent properties, the lifetimes and the temperature-dependent luminescence characteristic of the phosphors were investigated. Through an effective energy transfer, the emission spectra of GdAl₃(BO₃)₄:Ce³⁺, Tb³⁺ phosphor contains both a broad band in the range of 330–400 nm originated from Ce³⁺ ions and a series of sharp peaks at 484, 541, 583, and 623 nm due to Tb³⁺ ions. The energy transfer from Ce³⁺ to Tb³⁺ in GdAl₃(BO₃)₄ host is demonstrated to be phonon assisted nonradiative energy transfer via a dipole–dipole interaction.     

Insight into luminescent properties,energy transfer and thermal stability of NaBa4(AlB4O9)2Cl3:Ce3+, Tb3+ phosphors

A series of Ce³⁺ and Tb³⁺ singly- and co-doped NaBa₄(AlB₄O₉)₂Cl₃ (NBAC) phosphors have been synthesized via high-temperature solid state route. The crystal structure, morphology, photoluminescent properties, thermal properties and energy transfer process between Ce³⁺ and Tb³⁺ were systematically investigated. The structure refinements indicated that the phosphors based on NBAC crystallized in P42nm polar space group in monoclinic phase. The emission color could be tuned from blue (0.1595, 0.0955) to green (0.2689, 0.4334) via changing the ratio of Ce³⁺/Tb³⁺. The energy transfer mechanism of Ce³⁺/Tb³⁺ was verified to be dipole–quadrupole interaction via the examination of decay times of Ce³⁺ based on Dexter's theory. The good thermal stability showed the intensities of Ce³⁺ at 150°C were about 66.9% and 64.88% in NBAC:0.09Ce³⁺ and NBAC:0.09Ce³⁺, 0.07Tb³⁺ of that at room temperature, and the emission intensities of Tb³⁺ remained 102.41% in NBAC:0.11Tb³⁺ and 95.22% in NBAC:0.09Ce³⁺, 0.07Tb³⁺ due to the nephelauxetic shielding effect and the highly asymmetric rigid framework structure of NBAC. The maximum external quantum efficiency (EQE) of Ce³⁺ in NBAC:0.09Ce³⁺, yTb³⁺ phosphors could reach 43.38% at y = 0.13. Overall, all the results obtained suggested that NBAC:Ce³⁺, Tb³⁺ could be a promising option for n-UV pumped phosphors.     

Tunable photoluminescence of apatite phosphor Ca5.95−xSrxLa4(SiO4)2(PO4)4O2:0.05Eu2+ and its application in light-emitting diodes

A series of new apatite phosphors Ca_5.95−xSr_xLa₄(SiO₄)₂(PO₄)₄O₂:0.05Eu²⁺ (x = 0-5.95) were prepared with the solid-state method. The variations of the occupation rate and cell parameters were investigated in detail, demonstrating that the phosphors are pure phases and that the different occupation rates of La³⁺, Ca²⁺, and Sr²⁺ ions are due to the different electrostatic bond strengths. The reflectance and photoluminescence excitation spectra prove that the phosphors can be efficiently excited with near-ultraviolet (n-UV) light. The broad redshift (50 nm) in the photoluminescence spectra is attributed to the increase in the crystal field splitting when the Ca²⁺ ion is replaced by the larger Sr²⁺ ion. At 150°C, the obtained phosphors maintain an emission intensity of ~67%-77% of that at room temperature (25°C), which indicates relatively the high performance of apatite phosphors in the temperature-dependence experiment. Because of the substitution of the small Ca²⁺ ion by the large Sr²⁺ ion, the emission color changes from green to yellow. Finally, a series of self-made light emitting diodes lamps were fabricated by coating the Ca_5.95−xSr_xLa₄(SiO₄)₂(PO₄)₄O₂:0.05Eu²⁺ phosphors with commercial blue and red phosphors on an n-UV chip (λ_ex = 370 nm). The self-made white-emitting lamps display a continuous changing correlated color temperature (4053-9353 K) or commission international de L'eclairgae (from [0.29, 0.28] to [0.38, 0.37]), implying that the series apatite phosphors have great potential to meet the different requirements of applications.     

Cyan-emitting Ba0.45Ca2.5La6(SiO4)6: 0.05 Eu2+ and Ba1.45Ca1.5La6(SiO4)6:0.05 Eu2+ solid-solution phosphors for white light-emitting diodes

Two cyan-emitting phosphors with different bandwidths were successfully synthesized through the high-temperature solid-state method in a reducing atmosphere. The crystal structures, morphologies, and luminescence properties of the as-prepared phosphors were investigated. The Rietveld refinements of the powder X-ray diffraction (XRD) data demonstrated the single phase of the samples, and two crystallographic sites of La³⁺ were observed in the crystal structure. Under the excitation of UV light, both Ba_0.45Ca_2.5La₆(SiO₄)₆: 0.05 Eu²⁺ and Ba_1.45Ca_1.5La₆(SiO₄)₆: 0.05 Eu²⁺ phosphors emitted cyan light due to the 4f⁶5 d¹→4f⁷ transitions of the Eu²⁺ ion. The emission spectra could be well fitted by two component Gaussian peaks corresponding to two different coordination environments of the Eu²⁺ ions. The temperature-dependent photoluminescence spectra show a large difference on the thermal stability between the two phosphors. The two phosphors exhibit effective absorption of near-UV light and their internal quantum efficiencies (IQEs) were calculated as 31.5% and 42.4% under 295 nm UV-light excitation. The experimental results indicate that the novel cyan phosphors might have potential applications in white light-emitting diodes (LEDs) based on the near-UV LED chip.     

A New Blue‐Emitting Phosphor of Ce3+‐Activated Fluorosilicate Apatite Ba2Y3[SiO4]3F

Blue‐emitting phosphor of Ce³⁺‐activated fluorosilicate apatite Ba₂Y₃[SiO₄]₃F was prepared via conventional solid‐state reaction method. The X‐ray powder diffraction (XRD), scanning electron microscopy (SEM), photoluminescence (PL) excitation and emission spectra, and the decay curves (lifetimes) were applied to characterize the phosphors. The effects of Ce³⁺ activator concentration on the luminescence properties were investigated. Ba₂Y_2.85Ce_0.15[SiO₄]₃F exhibits the brightest blue emission with CIE coordinates of (x = 0.231, y = 0.301). The crystallographic site of Ce³⁺ ions in Ba₂Y₃[SiO₄]₃F lattices was identified. Two kinds of crystallographic Ce³⁺ occupying MI and MII sites in Ba₂Y₃[SiO₄]₃F lattices result in two distinct emission centers. The internal PL quantum efficiency, the temperature‐dependent luminescence, and the activation energy of thermal quenching were investigated to evaluate the potential application. This is a new kind of blue‐emitting phosphor based on apatite structure.     

Visible Quantum Cutting and Energy Transfer in Tb3+‐Doped KSr(Gd,Y)(PO4)2 Under VUV–UV Excitation

KSr(Gd,Y)(PO₄)₂: Tb³⁺ phosphors were synthesized using the high‐temperature solid‐state reaction method. The VUV–UV spectroscopic properties of these phosphors were studied. The results show that efficient energy transfer (ET) from Gd³⁺ to Tb³⁺ occurs in this system, and the ET efficiency increases with increasing of Tb³⁺ doping concentrations, which is evidenced that both the emission intensity and decay time of Gd³⁺ decreases with increasing Tb³⁺ doping concentrations. Visible quantum cutting via cross relaxation between the neighboring Tb³⁺ ions was observed in the high Tb³⁺ concentration doped sample. In addition, the emission color of KSr(Gd,Y)(PO₄)₂: Tb³⁺ phosphors can be tuned from blue to yellowish‐green by varying the doping concentration of Tb³⁺. Under 147 nm excitation, the sample KSrGd_0.5(PO₄)₂: 0.5Tb³⁺ exhibits the strongest emission, which is about 70% of the commercial green‐emitting phosphor Zn₂SiO₄: Mn²⁺ indicating the potential application of this phosphor for plasma display panels, Hg‐free lamps, and three‐dimensional displays.     

Luminescence properties and energy transfer investigations of Sr2B2O5:Ce3+,Tb3+ phosphors

Ce³⁺ and Tb³⁺ co-doped Sr₂B₂O₅ phosphors were synthesized by the solid-state method. X-ray diffraction (XRD) was used to characterize the phase structure. The luminescent properties of Ce³⁺ and Tb³⁺ co-doped Sr₂B₂O₅ phosphors were investigated by using the photoluminescence emission, excitation spectra and reflectance spectra, respectively. The excitation spectra indicate that this phosphor can be effectively excited by near ultraviolet (n-UV) light of 317 nm. Under the excitation of 317 nm, Sr₂B₂O₅:Ce³⁺,Tb³⁺ phosphors exhibited blue emission corresponding to the f–d transition of Ce³⁺ ions and green emission bands corresponding to the f–f transition of Tb³⁺ ions, respectively. The Reflectance spectra of the Sr₂B₂O₅:Ce³⁺,Tb³⁺ phosphors are noted that combine with Ce³⁺ and Tb³⁺ ion absorptions. Effective energy transfer occurred from Ce³⁺ to Tb³⁺ in Sr₂B₂O₅ host due to the observed spectra overlap between the emission spectrum of Ce³⁺ ion and the excitation spectrum of Tb³⁺ ion. The energy transfer efficiency from Ce³⁺ ion to Tb³⁺ ion was also calculated to be 90%. The phosphor Sr₂B₂O₅:Ce³⁺,Tb³⁺ could be considered as one of double emission phosphor for n-UV excited white light emitting diodes.     

Synthesis and photoluminescence characterizations of Zn2+ and Tb3+ codoped CeO2 phosphors for temperature sensing applications

Cyan light-emitting Ce_0.985-xZn_xO₂:0.015 Tb³⁺ (x = 0 to 0.2) phosphors were synthesized using the ethylenediaminetetraacetic acid-assisted hydrothermal method. The X-ray diffraction and refinement analyses of the prepared phosphors indicated that the formed face-centered cubic structure remained intact even after the doping of large quantities of Zn²⁺ ions. However, the incorporation of Zn²⁺ ions increased the Ce³⁺/Ce⁴⁺ ratio, resulting in the enhancement of oxygen vacancies in the prepared phosphors. The generation of oxygen vacancies caused the evolution of a broad photoluminescence emission band ranging from 400 to 525 nm with a characteristic Tb³⁺ emission of approximately 543 nm. Two-emission regions in Ce_0.885Zn_0.1O₂:0.015 Tb³⁺ phosphors were utilized for measuring the fluorescence intensity ratio (FIR) as a function of temperature ranging from 303 to 523 K. At 523 K, the FIR values dropped to approximately 40% of the starting temperature value. The variation of FIR values followed the Boltzmann behavior. The Boltzmann fitting demonstrated the feasibility of the present phosphors for temperature sensor applications. The optimum absolute sensor sensitivity of Ce_0.885Zn_0.1O₂:0.015 Tb³⁺ phosphors was measured to be 0.0043 K⁻¹ at 398 K with a resolution of approximately 1 K⁻¹. Moderate temperature sensitivity, negligible hysteresis loop, and excellent reversibility revealed the suitability of Ce_0.885Zn_0.1O₂:0.015 Tb³⁺ phosphors for sensing the temperature in various electronic devices.     

Single phase multi color emitting Ca2LuTaO6: Dy3+/Eu3+ double perovskite oxide phosphors

The trivalent rare-earth (RE³⁺) doped phosphors show tremendous achievement in narrow band multicolor line emission for various applications. However, the 4f–4f absorption transition of these ions is forbidden in UV and blue light excitation. Usually, a sensitizer having spin allowed transition was used as a co-dopant to excite these ions via the energy transfer phenomenon. Another approach promisingly using to excite these ions by efficient energy transfer from the intrinsic emission of the Ca₂LuTaO₆ double perovskite phosphors host lattice. Phosphors of Ca₂LuTaO₆ with double perovskite structure were synthesized by using a high-temperature solid-state reaction method. The produced Ca₂LuTaO₆ double perovskite phosphors show an intrinsic broad band emission centered at 424 nm under the excitation of 313 nm UV light. The origin of this broad band blue emission was deeply investigated by using computation and experimental approaches. The trivalent activator Dy³⁺ and Eu³⁺ were doped is a single and co-dopant in the produced Ca₂LuTaO₆ phosphors to check their excitation in UV and near-UV spectral region. X-ray diffraction and scanning electron microscopy were used to investigate the structure and phase analysis. Various characterizations such as photoluminescence excitation, emission, and CIE chromaticity coordinates were measured which illustrate the potential of Dy³⁺ and Eu³⁺ activated Ca₂LuTaO₆ double perovskite phosphors for narrow band multicolor line emission for various applications.     

Enhanced luminescence properties and energy transfer in Ce3+ and Tb3+ co-doped NaCaBO3 phosphor

A series of color-tunable NaCaBO₃: Ce³⁺, Tb³⁺ phosphors have been synthesized on the basis of efficient Ce³⁺→Tb³⁺ energy transfer. The photoluminescence emission and excitation spectra, the lifetime, and the effect of Tb³⁺ concentration are investigated in detail. The enhanced photoluminescence of Tb³⁺ with sharp emission lines could be obtained by the broad excitation band from the allowed 4f–5d absorption of Ce³⁺ ions. The intensity ratio of blue emission from Ce³⁺ and green emission from Tb³⁺ can be tuned by adjusting their concentrations. The energy transfer from Ce³⁺ to Tb³⁺ in NaCaBO₃ was found to be an electric dipole–quadrupole interaction.     

Synthesis and Photoluminescence Characteristics of YAl3(BO3)4:Tb3+ Phosphors by Combustion Process

Terbium‐activated YAl₃(BO₃)₄ (YAl₃(BO₃)₄:Tb³⁺) phosphors were synthesized by both combustion method and solid‐state reaction. It was found that the pure‐phase YAl₃(BO₃)₄ phosphors synthesized by combustion method were obtained at 1000°C, which was 200°C lower than that by solid‐state reaction. The average particle size of the combustion‐derived phosphors increased with increasing temperatures. The luminescence characteristics in ultraviolet (UV) — vacuum ultraviolet (VUV) ranges for the YAl₃(BO₃)₄:Tb³⁺ phosphors were investigated. The bands from 175 nm to 300 nm were attributed to the 4f⁸‐4f⁷5d¹ transitions of Tb³⁺. The other strong bands in the region from 125 nm to 175 nm were assigned to host absorption. The emission spectra showed the strongest emission at 542 nm corresponding to the ⁵D₄→⁷F₅ transition of Tb³⁺. Moreover, the combustion‐derived YAl₃(BO₃)₄:Tb³⁺ phosphors generated more intense luminescence than the solid‐state‐derived phosphors under UV excitation.