NaBaY(BO3)2:Ce3+,Tb3+: A novel sharp green‐emitting phosphor used for WLED and FEDs

A new borate phosphor NaBaY(BO₃)₂: Ce³⁺, Tb³⁺ (NBY:Ce³⁺, Tb³⁺) was successfully synthesized under low temperature designed to put into application in the fields of ultraviolet (UV)‐excited light emitting diodes (LEDs) and field emission displays (FEDs). The structure distortion between Ce³⁺, Tb³⁺ single‐ and co‐doping NBY was discussed by X‐ray powder diffraction Rietveld refinement, high‐resolution transmission electron microscopy (HRTEM) and spectra. NBY: Ce³⁺, Tb³⁺ presents a wide absorption band ranging from 310 to 400 nm and efficient green emission (λ_max = 542 nm) with a full‐width at half‐maximum of 3.3 nm. The remarkable thermal stability has also been tested, indicating that the intensity at 200°C is still beyond 70% of the original intensity. In addition, a white LED device was manufactured by connecting a 370 nm UV chip with a blend of BaMaAl₁₀O₁₇: Eu²⁺ (BAM: Eu²⁺), NBY: Ce³⁺, Tb³⁺ and CaAlSiN₃: Eu²⁺. The color coordinate, correlated color temperature and color rendering index of the manufactured LED device were (0.335, 0.347), 5511 K and 80.16, respectively. Meanwhile, the cathodoluminescence (CL) spectra under the various conditions of probe currents and accelerating voltages were also analyzed. Through successive excitation of low‐voltage electron‐beam, the wonderful performances of degradation property and color stability were obtained. These results suggest that the green‐emitting NBY: Ce³⁺, Tb³⁺ phosphor has the prospect of becoming applications in white UV LEDs and FEDs.     

Tunable single-phase white-light-emitting Ba2Mg(BO3)2:Ce3+, Na+, Tb3+, Eu2+ phosphor based on energy transfer

A series of white-light-emitting phosphors of single-phase Ba₂Mg(BO₃)₂:Ce³⁺, Na⁺, Tb³⁺, Eu²⁺ were synthesized by conventional solid-state reaction. The crystal structure of the host was characterized by X-ray diffraction and investigated by Rietveld refinement. Photoluminescence properties were studied in detail. The energy transfer from Ce³⁺ to Tb³⁺ in Ba₂Mg(BO₃)₂ host was investigated and demonstrated to be a resonant type via a quadrupole–quadrupole mechanism. White light with wavelength tunable was realized by coupling the emission bands peaking at 417, 543 and 626 nm attributed to Ce³⁺, Tb³⁺ and Eu²⁺, respectively. By properly tuning the relative composition of Ce³⁺(Na⁺)/Tb³⁺/Eu²⁺, optimized Commission Internationale de l׳Eclairage (CIE) chromaticity coordinates (0.363, 0.295), high color rendering index (CRI) 90 and low correlated color temperature (CCT) 3793 K were obtained from the phosphor of Ba_1.90Ce_0.04Na_0.04Eu_0.02Mg_0.94Tb_0.06(BO₃)₂ upon the excitation of 296 nm UV radiation. These results indicate that Ba₂Mg(BO₃)₂:Ce³⁺, Na⁺, Tb³⁺, Eu²⁺ phosphor has a potential application as an UV radiation down-converting phosphor in white-light-emitting diodes.     

Novel Broadband Excited and Linear Red‐Emitting Ba2Y(BO3)2Cl: Ce3+, Tb3+, Eu3+ Phosphor: Luminescence and Energy Transfer

A series of Ce³⁺, Tb³⁺, Eu³⁺ tri‐doped Ba₂Y(BO₃)₂Cl red‐emitting phosphor have been synthesized by solid‐state method. The Ce³⁺→Tb³⁺→Eu³⁺ energy‐transfer scheme has been proposed to realize the sensitization of Eu³⁺ ion emission by Ce³⁺ ions. Following this energy‐transfer model, near‐UV convertible Eu³⁺‐activated red phosphors have been obtained in Ba₂Y(BO₃)₂Cl: Ce³⁺, Tb³⁺, Eu³⁺ phosphors. Energy transfers from Ce³⁺ to Tb³⁺, and Tb³⁺ to Eu³⁺, as well as corresponding energy‐transfer efficiencies are investigated. The combination of narrow‐line red emission and near‐UV broadband excitation makes Ba₂Y(BO₃)₂Cl: Ce³⁺, Tb³⁺, Eu³⁺ as a novel and efficient red phosphor for NUV LED applications.     

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.     

Tuning the Color Emission of Sr2P2O7: Tb3+, Eu3+ Phosphors Based on Energy Transfer

A series of color tunable Tb³⁺‐ and Eu³⁺‐activated Sr₂P₂O₇ phosphors were synthesized by a traditional solid‐state reaction method in air atmosphere. The crystal structure, photoluminescence (PL) properties, energy transfer, thermal stability, and luminous efficiency were investigated. A series of characteristic emission of Tb³⁺ and Eu³⁺ were observed in the PL spectra and the variation in the emission intensities of the three emission peaks at around 416 nm (blue), 545 nm (green), and 593 nm (orange‐red) induced the multicolor emission evolution by tuning the Tb³⁺/Eu³⁺ content ratio. The energy‐transfer mechanism from Tb³⁺ to Eu³⁺ ion was determined to be dipole–dipole interaction, and the energy‐transfer efficiency was about 90%. The novel phosphors have excellent thermal stability in the temperature range of 77–473 K and the Commission International De L'Eclairage 1931 chromaticity coordinates of Sr₂P₂O₇: Tb³⁺, Eu³⁺ (λ_ex = 378 nm) move toward the ideal white light coordinates.     

LiCaAlN2:Eu3+/Tb3+: Red and green phosphors for LEDs and FEDs with charge transfer transition in n‐UV region

LiCaAlN₂:Eu³⁺/Tb³⁺ red/green phosphors were successfully prepared by conventional solid‐state reaction. The photoluminescence (PL) properties and cathodoluminescence (CL) properties of LiCaAlN₂:Eu³⁺/Tb³⁺ were investigated in detail. The Eu³⁺ (Tb³⁺) doped LiCaAlN₂ shows red (green) emission peaking at 615 nm (550 nm). Monitored at 615 nm (550 nm), it is interesting to found that LiCaAlN₂:Eu³⁺ (LiCaAlN₂:Tb³⁺) has a broad charge transfer transition in the range of 350‐450 nm (275‐375 nm) peaking at 380 nm (343 nm), which can be efficiently excited by n‐UV light‐emitting diodes (LEDs). Under electron beam excitation, LiCaAlN₂:Tb³⁺ exhibited a good resistance to the current saturation. The white LED has also been fabricated with blue, green, and LiCaAlN₂:Eu³⁺ red phosphor. The results indicate that LiCaAlN₂:Eu³⁺/Tb³⁺ could be conducive to the development of phosphor‐converted LEDs and field emission displays (FEDs).     

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.     

Photoluminescence Properties of Color‐Tunable Ca3La6(SiO4)6: Ce3+, Tb3+ Phosphors

A series of newly developed color‐tunable Ca₃La₆(SiO₄)₆: Ce³⁺, Tb³⁺ phosphors were successfully prepared in this study. The crystal structures of the prepared phosphors were revealed to be hexagonal with space group P6₃/m, and the lattice parameters were evaluated via utilizing the Rietveld refinement method. Upon excitation at 288 nm, the emission spectra of Ce³⁺and Tb³⁺ ions co‐doped Ca₃La₆(SiO₄)₆ phosphors included a blue emission band and several emission lines. The blue emission band with a peak at 420 nm originated in the f–d transitions of Ce³⁺ ions, and the emission lines in the range of 450–650 nm were assigned to the ⁵D₄ → ⁷F_J (J = 6, 5, 4, 3) transitions of Tb³⁺ ions. Increasing the doping content of Tb³⁺ ions considerably strengthened Tb³⁺ emission and reduced Ce³⁺ emission owing to the energy transfer from Ce³⁺ to Tb³⁺ ions. The mechanism of the energy transfer was confirmed to be a dipole–dipole interaction. The effective energy transfer from Ce³⁺ to Tb³⁺ ions caused a color shift from purplish‐blue to yellowish‐green. Color‐tunable Ca₃La₆(SiO₄)₆: Ce³⁺, Tb³⁺ phosphors have the potential to be utilized in light‐emitting diodes with proper modulation of the amount of Tb³⁺ ions.     

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.     

Precipitation Synthesis and Color‐Tailorable Luminescence of α‐Zr(HPO4)2: RE3+(RE = Eu,Tb) Nanosheet Phosphors

The rare earth (RE = Eu and Tb) ions‐doped α‐Zr(HPO₄)₂ (ZrP) nanosheet phosphors were synthesized by direct precipitation method, and their structures and photoluminescence properties were investigated. The results of X‐ray diffraction and scanning electron microscopy indicated that the systems of ZrP:RE³⁺ had similar nanosheet structure except with relatively larger interlayer spacing as compared with pure α‐ZrP. Under the excitation of UV light, the ZrP:RE³⁺ nanosheet phosphors showed red and green emission peaks corresponding to the ⁵D₀→⁷F₂ transition of Eu³⁺ and the ⁵D₄→⁷F₅ transition of Tb³⁺, respectively. After Eu³⁺ and Tb³⁺ were co‐doped in ZrP host, not only the red and green emission peaks were simultaneously observed, but also the luminescent intensity and fluorescence lifetimes of Tb³⁺ were gradually decreased with the increase in Eu³⁺‐doping concentration, which implied the energy transfer from Tb³⁺ to Eu³⁺ happened. It was deduced that the energy transfer from Tb³⁺ to Eu³⁺ occurred via exchange interaction. Through optimization to the samples, a nearly white‐light emission with the color coordinate (0.322, 0.263) was achieved under 377 nm excitation. The ZrP:RE³⁺ nanosheet phosphors may be a potential color‐tailorable candidate for fabricating optoelectronic devices such as electroluminescence panels.     

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.     

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.     

Synthesis and photoluminescent properties of high-efficient color-tunable Ba3Y2B6O15: Ce3+, Tb3+ phosphors

High-efficient Ce³⁺/Tb³⁺ co-doped Ba₃Y₂B₆O₁₅ phosphors with multi color-emitting were firstly prepared, and their structural and luminescent properties were studied by XRD Rietveld refinement, emission/excitation spectra, fluorescence lifetimes as well as temperature-variable emission spectra. Upon 365?nm excitation, the characteristic blue Ce³⁺ band along with green Tb³⁺ peaks were simultaneously found in the emission spectra. Moreover, by increasing concentration of Tb³⁺, a blue-to-green tunable emitting color could be realized by effective Ce³⁺→Tb³⁺ energy transfer. Furthermore, all Ba₃Y₂B₆O₁₅: Ce³⁺, Tb³⁺ phosphors exhibit high internal quantum efficiency of ~?90%, while the temperature-variable emission spectra reveal that the phosphors possess impressive color stability as well as good thermal stability (T₅₀ =?~?120?°C). The results indicate that these efficient color-tuning Ba₃Y₂B₆O₁₅: Ce³⁺, Tb³⁺ might be candidate as converted phosphor for UV-excited light-emitting diodes.     

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.     

A novel Eu2+/Tb3+ co-doped phosphor with pyroxene structure applied for cryogenic thermometric sensing

Pyroxene-type phosphors were widely developed due to the advantages of high chemical stability, luminous efficiency, and low production cost. In this contribution, a series of Eu²⁺/Tb³⁺ co-doped Ca_0.75Sr_0.2Mg_1.05Si₂O₆ (CSMS) phosphors with pyroxene structure were successfully synthesized by the solid-state method. Under the 340 nm excitation, the emission peaks of the phosphor show a redshift with the increase of Eu²⁺ concentration. The emitting color of Eu²⁺/Tb³⁺ co-doped samples shows a redshift attributed to the energy transfer from Eu²⁺ to Tb³⁺. Simultaneously, acquired thermometer exposes superbly temperature-sensitive properties (S_a and S_r having maximum values 4.7% K⁻¹ and 0.6% K⁻¹, respectively) over the cryogenic temperature range (77–280 K). Furthermore, it has good stability and precision at cryogenic temperatures, indicating that CSMS:0.03Eu²⁺/0.03Tb³⁺ phosphor is a very promising fluorescent material suitable for cryogenic temperature sensing.     

Preparation,luminescence properties and energy transfer of Ca9Y(PO4)7: Eu2+‐Tb3+ phosphors

Tb³⁺‐doped and Eu²⁺, Tb³⁺ co‐doped Ca₉Y(PO₄)₇ phosphors were synthesized by conventional solid‐state method. Additionally, the luminescence properties, decay behavior and energy transfer mechanism have already been investigated in detail. The green emission intensity of Tb³⁺ ions under NUV excitation is weak due to its spin‐forbidden f‐f transition. While Eu²⁺ can efficiently absorb NUV light and yield broad blue emission, most of which can be absorbed by Tb³⁺ ions. Thus, the emission color can be easily tuned from cyan to green through the energy transfer of Eu²⁺→Tb³⁺ in Ca₉Y(PO₄)₇:Eu²⁺,Tb³⁺ phosphor. In this work, the phenomenon of cross‐relaxation between ⁵D₃ and ⁵D₄ are also mentioned. The energy transfer is confirmed to be resulted from a quadrupole‐quadrupole mechanism.     

Tunable luminescence and energy transfer properties of MgY4Si3O13: Ce3+, Tb3+, Eu3+ phosphors

The tricolor-emitting MgY₄Si₃O₁₃: Ce³⁺, Tb³⁺, Eu³⁺ phosphors for ultraviolet-LED have been prepared via a high-temperature solid-state method. X-ray diffraction, photoluminescence emission, excitation spectra and fluorescence lifetime were utilized to characterize the structure and the properties of synthesized samples. Two different lattice sites for Ce³⁺ are occupied from the host structure and the normalized PL and PLE spectra. The emissions of single-doped Ce³⁺/Tb³⁺/Eu³⁺ are located in blue, green and red region, respectively. The energy transfer from Ce³⁺ to Tb³⁺ and from Tb³⁺ to Eu³⁺ has been validated by spectra and decay curves and the energy transfer mode from Tb³⁺ to Eu³⁺ was calculated to be electric dipole-dipole interactions. By adjusting the content of Tb³⁺ and Eu³⁺ in MgY₄Si₃O₁₃: Ce³⁺, Tb³⁺, Eu³⁺, the CIE coordinates can be changed from blue to green and eventually generate white light under UV excitation. All the results indicate that the MgY₄Si₃O₁₃: Ce³⁺, Tb³⁺, Eu³⁺ phosphors are potential candidates in the application of UV-WLEDs.     

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.     

The Energy Transfer and Thermal Stability of a Blue‐Green Color Tunable K2CaP2O7:Ce3+,Tb3+ Phosphor

Novel blue‐green emitting Ce³⁺‐ and Tb³⁺‐activated K₂CaP₂O₇ (KCPO) luminescent materials were synthesized via a solid‐state reaction method. X‐ray diffraction, luminescence spectroscopy, decay time, and fluorescent thermal stability tests have been used to characterize the prepared samples. The KCPO:Ce³⁺,Tb³⁺ luminescence spectra show broad band of Ce³⁺ ions and characteristic line of Tb³⁺ ion transition (⁵D₄–⁷F₅). The color variation in the light emitting from blue to green under UV excitation can be obtained by tailoring the Tb³⁺ content in KCPO:Ce³⁺. Besides, Ce³⁺ ions obviously intensify Tb³⁺ ion emission through an effective energy transfer process, which was confirmed from decay curves. The energy transfer efficiency was determined to be 82.51%. A resonant type mechanism via the dipole–quadrupole interaction can be proposed for energy transfer. As a whole, the KCPO:Ce³⁺,Tb³⁺ phosphor exhibits excellent performance in the range from 77 to 673 K, indicating the phosphors are highly potential candidates for solid‐state lighting.     

Enhanced red emission and improved thermal quenching of CaAlSiN3:Eu2+ phosphors via boron doping

The development of high-performance phosphors is required for phosphor-converted white light-emitting diodes. However, most approaches are unable to achieve optimum emission intensity and thermal quenching simultaneously. Here, a series of CaAlSiN₃:Eu²⁺ (CASN:Eu²⁺) red-emitting phosphors doped with B were synthesized using field-assisted sintering technology. Compared with CASN:Eu²⁺, the B-doped phosphor exhibited high external quantum efficiency (EQE) and good thermal quenching performance. With boron doping, the EQE of CaAlSiN₃:Eu²⁺ shows an obvious growth, increasing from 48.83% to 70.68%. Meanwhile, thermal quenching performance has also been greatly improved, which is strongly associated with the band structure of Eu²⁺ and the crystal structure of CASN. The location of B in the crystal lattice was studied and the mechanism of improving thermal quenching via B doping was discussed in detail. Finally, a white LED fabricated by the combination of a GaN blue chip (450 nm) with the as-synthesized red phosphors and Y₃(Al, Ga)₅O₁₂:Ce³⁺ green phosphors (531 nm), shows a high color rendering index (Ra =91.6). This study offers a novel method to improve luminescence properties of CASN:Eu²⁺ red-emitting phosphors, which may broaden their application in solid-state lighting devices.