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To reduce the issue of tri-primary color reabsorption, a new approach for single-phase phosphors as light-emitting diodes (LEDs) has been recommended. The structures, morphology, photoluminescence, thermal stability, and luminescence mechanism of a variety of Ca3Bi (PO4)3 (CBPO): Ce3+/Dy3+ phosphors were investigated. XRD characterization showed that all CBPO samples were eulytite structures. Furthermore, the energy transfer process from Ce3+ to Dy3+ in CBPO is systematically investigated in this work, and the color of light can be adjusted by changing the ratio of doped ions. Under UV light, energy is transferred from Ce3+-Dy3+ mainly through quadrupole-quadrupole interactions in the CBPO host, and doping with different Dy3+ concentrations tunes the emission color from blue to white. The thermal stability of the CBPO: 0.04Ce3+, 0.08Dy3+ samples is outstanding, and the CIE coordinates of the samples after emission have little effect with temperature, while their emission intensity at 423 K is as strong as that at room temperature, reaching 90%. The above results indicate that this CBPO material has great potential as a white light phosphor under near-UV excitation at the optimized concentration of Ce3+ and Dy3+. [ABSTRACT FROM AUTHOR]

Although large amount of effort has been invested in combating thermal quenching that severely degrades the performance of luminescent materials particularly at high temperatures, not much affirmative progress has been realized. Herein, we demonstrate that the Frenkel defect formed via controlled annealing of Sc2(WO4)3:Ln (Ln=Yb, Er, Eu, Tb, Sm), can work as energy reservoir and back‐transfer the stored excitation energy to Ln3+ upon heating. Therefore, except routine anti‐thermal quenching, thermally enhanced 415‐fold downshifting and 405‐fold upconversion luminescence are even obtained in Sc2(WO4)3:Yb/Er, which has set a record of both the Yb3+‐Er3+ energy transfer efficiency (>85 %) and the working temperature at 500 and 1073 K, respectively. Moreover, this design strategy is extendable to other hosts possessing Frenkel defect, and modulation of which directly determines whether enhanced or decreased luminescence can be obtained. This discovery has paved new avenues to reliable generation of high‐temperature luminescence. [ABSTRACT FROM AUTHOR]

Although large amount of effort has been invested in combating thermal quenching that severely degrades the performance of luminescent materials particularly at high temperatures, not much affirmative progress has been realized. Herein, we demonstrate that the Frenkel defect formed via controlled annealing of Sc2(WO4)3:Ln (Ln=Yb, Er, Eu, Tb, Sm), can work as energy reservoir and back‐transfer the stored excitation energy to Ln3+ upon heating. Therefore, except routine anti‐thermal quenching, thermally enhanced 415‐fold downshifting and 405‐fold upconversion luminescence are even obtained in Sc2(WO4)3:Yb/Er, which has set a record of both the Yb3+‐Er3+ energy transfer efficiency (>85 %) and the working temperature at 500 and 1073 K, respectively. Moreover, this design strategy is extendable to other hosts possessing Frenkel defect, and modulation of which directly determines whether enhanced or decreased luminescence can be obtained. This discovery has paved new avenues to reliable generation of high‐temperature luminescence. [ABSTRACT FROM AUTHOR]

Different from organic dye/quantum dot possessing one luminescent center, upconversion luminescence (UCL) is actually a statistic of temporal behaviors of countless individual activators. Our experimental results have shown that the rise and decay dynamics of UCL is directly associated with the relative contribution of sensitizer‐to‐activator energy transfer and energy migration among sensitizers, which can be physically modulated by simply tuning the excitation laser. Therefore, dynamic UCL with record‐wide 20‐fold lifetime, ≈70‐fold red‐to‐green intensity ratio, and reversibly definable emission color is easily realized by just modulating the excitation laser. Moreover, this generally applicable strategy only requires a simplest‐possible UCL system whereas prevalent material engineering such as complicated composition design, sophisticated core–shell construction, or tedious chemical synthesis, is no longer needed. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Ce3+,Dy3+ and Tb3+ doped BaZn2(PO4)2 phosphors were prepared via a high temperature solid state reaction route. The crystal structure, photoluminescence properties, decay lifetime, luminous efficiency and thermal stability of the phosphors were investigated. The mechanism of Ce3+–Dy3+/Tb3+ energy transfer was determined to be a dipole–dipole interaction based on the photoluminescence spectra and decay curves of the phosphors. The critical distance between the Ce3+ and Dy3+/Tb3+ ions was calculated using both the concentration quenching method and the spectral overlap method. Tunable emission from blue to bluish white and green can be realized by energy transfer and changing the doping concentrations of Dy3+ and Tb3+ under UV light. BaZn2(PO4)2:Ce3+,Dy3+/Tb3+ phosphors are proved to be promising candidates in the lighting field due to their excellent thermal stability and luminescence properties. [ABSTRACT FROM AUTHOR]

The luminescent property of the Zn 2 P 2 O 7 : Dy 3+ was improved by co-doping Ce 3+ ion into phosphor. The photoluminescence intensity of Dy 3+ was remarkably enhanced by co-doping Ce 3+ . The enhance of emission intensity of Dy 3+ was proposed to be the energy transfer process between Ce 3+ and Dy 3+ which dominated by the electric dipole–dipole interaction, and the energy transfer efficiency is about 90%. The novel phosphors have excellent thermal stability and the emission intensity at 473 K only decreased by 9% than that at room temperature. Furthermore, the CIE 1931 chromaticity coordinates of Zn 2 P 2 O 7 : Ce 3+ , Dy 3+ were adjacent to the ideal white light coordinates, which points to its high potential for white light emitting. [ABSTRACT FROM AUTHOR]

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+ (λex = 378 nm) move toward the ideal white light coordinates. [ABSTRACT FROM AUTHOR]

A novel green light emitting phosphor Zn 2 P 2 O 7 : Ce 3+ , Tb 3+ was synthesized by the traditional solid state reaction method at 850 °C. The crystal structure, photoluminescence properties, thermal stability and luminous efficiency were investigated. Co-doping of Ce 3+ enhanced the emission intensity of Tb 3+ greatly by transferring its energy to Tb 3+ . Through an efficient energy transfer process, the obtained phosphors exhibit both the weak emission of Ce 3+ (5d–4f) and the strong emission of Tb 3+ ( 5 D 4 – 7 F J ) with considerable intensity. The energy transfer mechanism from Ce 3+ to Tb 3+ ion was determined to be dipole–dipole interaction, and the energy transfer efficiency was over 90%. The effect of Ce 3+ and Tb 3+ concentrations on luminescence in single and co-doped phosphors was also studied. The novel phosphors have excellent thermal stability and remarkable CIE chromaticity coordinates of (0.3149, 0.5652), which points to its high potential as green emitting phosphor in lighting field. [ABSTRACT FROM AUTHOR]

Abstract: A novel orange–red emitting Sr2P2O7:Eu3+, Gd3+ phosphor was synthesized by a traditional solid state reaction method in air atmosphere. The phase, photoluminescence properties, energy transfer and fluorescent thermal stability of as-prepared samples were investigated. Sr2P2O7 phase has a 3D-network structure, where [P2O7] groups connect with each other by corner sharing and Sr2+ ions locate at the polyhedral form in the P–O network. The orange–red emitting luminescence from Eu3+ with the aid of efficient energy transfer between Eu3+ and Gd3+ have been discussed in detail. Sr2P2O7:Eu3+, Gd3+ phosphor shows bright orange–red emission from Eu3+ with peaks around 592nm and 613nm under ultraviolet excitation. The novel phosphor showed weak thermal quenching and excellent luminescence properties, and are therefore of high potential as orange–red phosphor in lighting field. [Copyright &y& Elsevier]

Highlights: [•] A novel spherical phosphor was synthesized using microwave-assisted co-precipitation method. [•] The energy transfer mechanism of Ce3+–Tb3+ was discussed in detail. [•] The phosphors have excellent luminescence properties and thermal stability. [ABSTRACT FROM AUTHOR]

A novel color tunable phosphor was developed by a high-temperature solid-state reaction route with apatite-type Ca 8 NaGd(PO 4) 6 F 2 (CNGF) as matrix for the doping with Ce3+ and Tb3+ ions. The crystal structures were studied by XRD and Rietveld refinement, which clarified the structural parameters and the occupation of doped ions in crystal lattice. The luminescent intensity of Tb3+ ions was significantly improved by the energy transfer from Ce3+ to Tb3+ ions. According to the luminescence spectra and fluorescence decay curves of CNGF: Ce3+, Tb3+, a possible energy transfer mechanism was proposed. Fluorescent paper was prepared by binding the CNGF: Ce3+, Tb3+ phosphor particles with bacterial cellulose, and the morphology and luminescence properties of the paper were investigated. These results demonstrate that the obtained CNGF: Ce3+, Tb3+ is a promising green phosphor candidate for solid-state lighting and anti-counterfeiting applications. Anti-counterfeit paper was prepared by incorporating the phosphor into BC, it exhibits an outstanding mechanical flexibility and excellent green luminescence properties. Image 1 • Color tunable purplish blue-green emitting phosphors were synthesized. • The energy transfer mechanism in Ca 8 NaGd(PO 4) 6 F 2 : Ce3+, Tb3+ was discussed in detail. • The phosphors have excellent luminescence properties and thermal stability. • Anti-counterfeit paper was prepared by incorporating the phosphor into bacterial-cellulose. [ABSTRACT FROM AUTHOR]

A series of KAlP 2 O 7 : Tb3+, Eu3+ Phosphors with tunable green-yellow to red emission have been obtained utilizing Tb3+-Eu3+ energy transfer. • A novel Tb3+, Eu3+ co-doped KAlP 2 O 7 phosphor was firstly synthesis. • The energy transfer mechanism of Tb3+-Eu3+ was discussed in detail. • KAlP 2 O 7 : Tb3+, Eu3+ was color tunable from green to yellow and red. • The phosphor shows excellent thermal stability. A new multicolor-emitting Tb3+-Eu3+ codoped KAlP 2 O 7 (KAPO) phosphor was synthesized by solid-state reaction under the air atmosphere. The synthesis, morphology, luminescence properties, energy transfer mechanisms and thermal stability of the synthesized phosphor were systematically investigated. The codoped phosphor exhibited the characteristic emission of Eu3+ at 612 nm (5D 0 -7F 2) and Tb3+ at 544 nm (5D 4 -7F 5). Under ultraviolet (UV) excitation, KAPO: Tb3+, Eu3+ shows tunable emission from green-yellow to red with increasing of Eu3+ concentration due to efficient Tb3+-Eu3+ energy transfer. Based on the decay curves, the energy transfer from Tb3+ to Eu3+ was classified to be of dipole-dipole interaction resonant type with energy transfer efficiency of ~97%. The excellent luminescent properties and remarkable thermal stabilities suggested that KAPO: Tb3+, Eu3+ is a promising UV-converting material for the fields of lighting and displays. [ABSTRACT FROM AUTHOR]

Although large amount of effort has been invested in combating thermal quenching that severely degrades the performance of luminescent materials particularly at high temperatures, not much affirmative progress has been realized. Herein, we demonstrate that the Frenkel defect formed via controlled annealing of Sc2(WO4)3:Ln (Ln=Yb, Er, Eu, Tb, Sm), can work as energy reservoir and back‐transfer the stored excitation energy to Ln3+ upon heating. Therefore, except routine anti‐thermal quenching, thermally enhanced 415‐fold downshifting and 405‐fold upconversion luminescence are even obtained in Sc2(WO4)3:Yb/Er, which has set a record of both the Yb3+‐Er3+ energy transfer efficiency (>85 %) and the working temperature at 500 and 1073 K, respectively. Moreover, this design strategy is extendable to other hosts possessing Frenkel defect, and modulation of which directly determines whether enhanced or decreased luminescence can be obtained. This discovery has paved new avenues to reliable generation of high‐temperature luminescence. [ABSTRACT FROM AUTHOR]

Although large amount of effort has been invested in combating thermal quenching that severely degrades the performance of luminescent materials particularly at high temperatures, not much affirmative progress has been realized. Herein, we demonstrate that the Frenkel defect formed via controlled annealing of Sc2(WO4)3:Ln (Ln=Yb, Er, Eu, Tb, Sm), can work as energy reservoir and back‐transfer the stored excitation energy to Ln3+ upon heating. Therefore, except routine anti‐thermal quenching, thermally enhanced 415‐fold downshifting and 405‐fold upconversion luminescence are even obtained in Sc2(WO4)3:Yb/Er, which has set a record of both the Yb3+‐Er3+ energy transfer efficiency (>85 %) and the working temperature at 500 and 1073 K, respectively. Moreover, this design strategy is extendable to other hosts possessing Frenkel defect, and modulation of which directly determines whether enhanced or decreased luminescence can be obtained. This discovery has paved new avenues to reliable generation of high‐temperature luminescence. [ABSTRACT FROM AUTHOR]