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Novel green-red color-tunable Ca8(Mg,Mn)Tb(PO4)7:Eu2+ phosphors have been synthesized via the traditional solid-state method. Since Tb3+/Mn2+ ions are the parent ions in the lattice, the structural confinement occurs when the sensitizer Eu2+ is introduced into the Ca8(Mg,Mn)Tb(PO4)7:Eu2+ structure. The distance from Eu2+ to Tb3+/Mn2+ is confined in the 5 Å range, which induces a highly efficient energy transfer process. At Eu2+ 350 nm excitation, Ca8MgTb(PO4)7:Eu2+ shows dominant Tb3+ green emission with almost-vanished Eu2+ emission. Red emission is clearly observed as Mn2+ ions doping into Ca8MgTb(PO4)7:Eu2+, and color-tuning from green to red is realized by varying the Mn2+ contents. Eu2+–Tb3+–Mn2+ cascade energy transfer process is in effect due to short Eu2+–Tb3+/Mn2+ and Tb3+–Mn2+ distances, which is verified by PL and decay variations. Meanwhile, the Ca8(Mg,Mn)Tb(PO4)7:Eu2+ phosphor indicates good thermal stability and maintained the 45% emission level at 150 °C, which demonstrates their potential applications in white light LEDs. [ABSTRACT FROM AUTHOR]

A new dual-emitting phosphor K 2 BaCa(PO 4) 2 : Ce3+, Tb3+ (KBCP: Ce3+, Tb3+) was successfully synthesized and designed to put into application of ratiometric temperature sensing. Under single UV excitation, the developed phosphors shows both Ce3+ violet and Tb3+ green emission mainly at 360 and 542 nm, respectively. The Ce3+-Tb3+ energy transfer process was analyzed by the variation of emission spectra and Ce3+/Tb3+ decay lifetimes. The remarkable thermal stability has also been tested, indicating that the intensity at 200 °C is still above 85% of the original intensity. Furthermore, the emission intensity ratio between 360 and 542 nm of KBCP: Ce3+, Tb3+ is found to have a good linear relationship with temperature (R 2 > 0.993), and the corresponding sensitivity temperature resolution is 0.35% K−1 and >0.02 K, respectively. Thus, this novel dual-emitting phosphor can be used as a potential luminescent thermometer. [ABSTRACT FROM AUTHOR]

Graphical abstract A high-efficient and thermochromic phosphor Na 3 Sc 2 P 3 O 12 : Eu2+, Mn2+ is synthesized by solid-state reaction. The phosphor exhibits blue (Eu2+) and red (Mn2+) dual-emission with high quantum efficiency of 98%. The dual-emissions has different thermal dependencies due to the competition between thermal-activated energy transfer and thermal quenching, thus enabling their intensity ratio to be highly sensitive to the temperature variation, which makes this phosphor a good candidate as ratiometric and colormetric temperature sensor. Highlights • Na 3 Sc 2 P 3 O 12 : Eu2+, Mn2+ dual-emitting and thermochromic phosphor was prepared by modified solid-state method. • The phosphor exhibits high-efficiency dual-emission under UV excitation (QE = 98%). • Ratio of emission intensities of Eu2+ to Mn2+ was linear dependent on the temperature. • The maximum relative sensitivity of this optical thermometer is 1.556% K−1. • The emitting color is dependent on the temperature which makes it suitable for safety sign. Abstract Dual-emitting and thermochromic Eu2+, Mn2+ co-doped Na 3 Sc 2 P 3 O 12 (NSPO) phosphor was synthesized by a modified solid-state method. Its crystal structure and luminescent properties, especially temperature-dependent fluorescence properties are discussed in detail. Na 3 Sc 2 P 3 O 12 : Eu2+, Mn2+ simultaneously exhibits two broad bands under single UV excitation, i.e. Eu2+ blue emission band centered at 460 nm and Mn2+ red emission band centered at 600 nm with quantum efficiency of >90%. The dual emissions in Na 3 Sc 2 P 3 O 12 : Eu2+, Mn2+ have different thermal responses due to the competition between trap-to-activator energy transfer and thermal quenching, by which a novel self-referencing non-invasion optical thermometer with high sensitivity and superior signal discriminability was designed. The temperature sensing properties of Na 3 Sc 2 P 3 O 12 : Eu2+, Mn2+ in a wide range of 293–473 K were analyzed, which shows good linear relationship between ratiometric intensity and temperature (R 2 > 0.999) as well as high sensitivity (1.556% K−1). Besides, the emitting color is highly sensitive to the temperature variation. The results suggest that Na 3 Sc 2 P 3 O 12 : Eu2+, Mn2+ could be a good candidate high-sensitive for optical thermometry and safety sign in high temperature environment. [ABSTRACT FROM AUTHOR]

Self-activated and Eu 3+ -doped vanadate phosphors Ca 3 LiZnV 3 O 12 were synthesized via the solid-state reaction route. The corresponding crystal structure, luminescence properties, energy transfer process and thermal stability were investigated. Ca 3 LiZnV 3 O 12 can be effectively excited by 340 nm near-ultraviolet light, and exhibits self-activated broadband cyan emission. Sensitized Eu 3+ red emissions were obtained in Ca 3 LiZnV 3 O 12 : Eu 3+ , where VO 4 3- groups acted as sensitizers by absorbing near ultraviolet photons and transferring them to Eu 3+ by energy transfer process. The emitting of Ca 3 LiZnV 3 O 12 : Eu 3+ could vary from cyan (0.264, 0.364) through white (0.389, 0.366) and to orange (0.494, 0.360) by controlling Eu 3+ concentration. All the results indicate that self-activated and Eu 3+ -doped Ca 3 LiZnV 3 O 12 could be potential candidate as UV-excited color-tunable phosphors. [ABSTRACT FROM AUTHOR]

Thermal quenching is one of the most crucial challenges for LED phosphors, in which the phosphor in LED device suffers from emission loss due to non-radiative transition with increasing temperature. Here, we report a broadband-excited and color-tunable LuVO 4 : Bi 3+ , Eu 3+ phosphor that does not exhibit thermal quenching even up to 200 °C. The phosphor shows Bi 3+ absorption broadband ranging from 250 to 400 nm, along with the sensitized Eu 3+ red emission lines. The emission color tuned from yellow with color coordinate (0.403, 0.507) to bright red (0.609, 0.370) as a function of Bi 3+ /Eu 3+ ratio. The phenomenon of zero thermal quenching originates from enhanced energy transfer (ET) from Bi 3+ 3 P 1 state to Eu 3+ 5 D 4 state through the population inversion from 3 P 0 to 3 P 1 at high temperature. Due to strong UV absorption, high quantum efficiency (∼76%) and excellent thermal stability, the as-prepared LuVO 4 : Bi 3+ , Eu 3+ phosphors can be potential candidates as red phosphors applied in UV-pumped LEDs. [ABSTRACT FROM AUTHOR]

A series of color-tunable green-red-emitting SrY(SiO): Tb, Eu (SYSO: Tb, Eu) were synthesized by solid-state method. The crystal structure and dopant-occupied sites of SYSO: Tb, Eu were investigated by XRD-Rietveld refinement. Furthermore, the corresponding luminescent properties were studied in detail. The energy transfer (ET) process from Tb to Eu was found to be resonant type via exchange interaction with ET efficiency of ~ 85%. By varying the Tb/Eu ratio, the emitting color can be tuned from green, yellow, orange and eventually to red. The temperature-dependent PL spectra revealed that SYSO: Tb, Eu phosphor has good thermal stability. All these properties indicate that the developed phosphor may potentially be used as single-component multicolor-emitting phosphors. [ABSTRACT FROM AUTHOR]

A series of broadband-excited and color-tunable Ba 2 Y 5 B 5 O 17 : Ce 3+ , Tb 3+ , Eu 3+ phosphors were synthesized using Ce 3+ -Tb 3+ -Eu 3+ energy transfer and their luminescent properties have been comprehensively studied. The Tb 3+ ions act as an energy transfer bridge between Ce 3+ -Eu 3+ ion pairs, which can alleviate metal-mediated charge transfer (MMCT) quenching. Therefore, the Eu 3+ linear red emission was efficiently sensitized by Ce 3+ broad excitation band through a Tb 3+ bridge. The emitting color of Ba 2 Y 5 B 5 O 17 : Ce 3+ , Tb 3+ , Eu 3+ phosphors could be tuned from blue through green and finally to red with increasing Tb 3+ /Eu 3+ content. By analyzing the variation of the emission intensity and decay lifetime of the sensitizer, it was found that the energy-transfer mechanism of Ce 3+ -Tb 3+ and Tb 3+ -Eu 3+ is dipole-quadrupole and exchange interactions, respectively. The phosphors exhibit high-efficient and blue-green-red color-tunable emission (QE > 40 %) and good thermal stability against temperature quenching ( T 50 > 473 K). [ABSTRACT FROM AUTHOR]

A dual-emitting phosphor LaOBr: Ce 3+ , Tb 3+ was synthesized, and the corresponding temperature-dependent luminescent properties were systematically investigated. The dual-emitting phosphor exhibits an exactly contrary thermal dependence with respect to the blue emission of the Ce 3+ sensitizer and the green emission of the Tb 3+ activator. The unique energy transfer between Ce 3+ and Tb 3+ enables this luminescent thermometer to be highly temperature-sensitive over a wide temperature range. The fluorescence intensity ratio (FIR) of the blue and green emission bands peaked at 430 and 543 nm is found to have a well-fitted linear relationship with respect to temperature, and the emitting color shifts from blue to green when temperature rises from 273 K to 493 K. The results indicate that Ce 3+ , Tb 3+ co-doped LaOBr phosphor is a potential candidate for a ratiometric and colorimetric luminescent thermometer. [ABSTRACT FROM AUTHOR]

A yellow phosphor Zn3V2O8: Bi3+ was synthesized by solid-state method. It can efficiently absorb UV photons of 250-400 nm, and convert into strong yellow emission with maximum at 550 nm, which can be absorbed by dye-sensitized solar cells ( DSSCs). VO4→Bi3+ energy transfer is discussed. The critical Bi3+ concentration is 0.04 with critical distance of 13.25 Å. The CIE coordinates of Zn3V2O8: Bi3+ are (0.421, 0.518). Zn3V2O8: Bi3+ phosphor exhibits good thermal stability with T1/2=150°C. The results indicate that Zn3V2O8: Bi3+ phosphor is a promising UV-absorbing spectral converter to enhance power conversion efficiency and photochemical stability of DSSCs. [ABSTRACT FROM AUTHOR]

A series of color-tunable phosphors Ca 10 Li(PO 4 ) 7 : Ce 3+ , Mn 2+ were synthesized by high-temperature solid-state reaction. Site occupancy of Ce 3+ and Mn 2+ in Ca 10 Li(PO 4 ) 7 and corresponding luminescent properties were systemically studied. Rietveld refinement results indicate that the Ce 3+ ions are preferred to occupy 7-cooridnated M1 and M3 sites, and Mn 2+ ions are mainly occupying distorted octahedral M5 sites, which results in Ce 3+ violet emission at 370 nm and Mn 2+ red emission at 640 nm. The intensity of Mn 2+ red emission is greatly enhanced through efficient Ce 3+ -Mn 2+ energy transfer ( η ET =94%). The critical distance and corresponding mechanism of Ce 3+ -Mn 2+ energy transfer was found to be ~11 Å and dipole-quadrupole interaction, respectively. The emitting colors of Ca 10 Li(PO 4 ) 7 : Ce 3+ , Mn 2+ phosphors can be tuned from violet through pink to red by adjusting the Ce 3+ /Mn 2+ ratio. The composition-optimized red phosphor Ca 10 Li(PO 4 ) 7 : 0.05Ce 3+ , 0.09Mn 2+ exhibits excellent thermal stability at high temperature (~100% at 160 °C). [ABSTRACT FROM AUTHOR]

Ce/Tb/Mn-codoped SrZnY(PO) (SZYP) white-emitting phosphors have been synthesized via solid-state reaction technology. The overlapping spectra between the excitation bands of Mn and Tb ions and the emission band of Ce suggest that Ce → Mn and Ce → Tb energy transfer occurs. The emission hues exhibited by Ce/Tb- and Ce/Mn-codoped phosphors could be modulated from bluish to greenish region and from bluish to reddish region by simply adjusting the relative content of Ce/Tb and Ce/Mn, respectively. SZYP:Ce,Tb,Mn samples exhibited three dominant bands at 410 nm, 545 nm, and 600 nm, attributable to electronic transitions of Ce, Tb, and Mn ions, respectively. Thus, color-tunable emission was achieved by accurately modulating the concentrations of Ce, Tb, and Mn ions. SZYP:0.05Ce,0.11Mn,0.11Tb was found to be an ideal white-light-emitting phosphor with color coordinates of (0.34, 0.33) and correlated color temperature of about 5144.83 K. The results indicate that Ce/Tb/Mn -tridoped SZYP phosphors are potential single-component white-emitting candidates for application in ultraviolet- and white-light-emitting diodes. [ABSTRACT FROM AUTHOR]

A series of violet-green-red color-tunable Ca 9 ZnK(PO 4 ) 7 : Ce 3+ /Tb 3+ /Mn 2+ phosphors were synthesized via high temperature solid-state method. The luminescence properties, energy transfer and thermal stability were investigated in detail. When doped with trivalent cerium, Ca 9 ZnK(PO 4 ) 7 : Ce 3+ presents strong violet luminescence under UV excitation. Incorporating Tb 3+ and Mn 2+ into Ca 9 ZnK(PO 4 ) 7 : Ce 3+ generates enhanced Tb 3+ green emission peak and Mn 2+ red emission band. The Ce 3+ sensitization effect on Tb 3+ and Mn 2+ is verified by the variation of PL/PLE spectra, Ce 3+ decay lifetimes and energy transfer efficiency of Ca 9 ZnK(PO 4 ) 7 : Ce 3+ , Tb 3+ /Mn 2+ phosphors. The color tone can be tuned from violet (0.196, 0.102) to green (0.343, 0.563) and to red (0.676, 0.311) by properly changing the ratio of Ce 3+ /Tb 3+ and Ce 3+ /Mn 2+ . The representative Ca 9 ZnK(PO 4 ) 7 : 0.01Ce 3+ , 0.07Tb 3+ sample shows good thermal stability with 95% of its room temperature PL intensity at 180 °C. These results indicate that Ca 9 ZnK(PO 4 ) 7 : Ce 3+ /Tb 3+ /Mn 2+ may be potential candidates as single-phase color-tunable phosphors for UV-convertible devices. [ABSTRACT FROM AUTHOR]

A series of broadband UV-excited and dual-emitting LaOBr: Ce 3+ , Tb 3+ phosphors were synthesized by solid state reaction. Luminescent property, energy transfer behavior, thermal stability and ratiometric temperature sensing performance were investigated. Under single NUV excitation, LaOBr: Ce 3+ , Tb 3+ exhibited both blue Ce 3+ emission band and sensitized green Tb 3+ emission peak, and the color of high-brightness emission can be tuned from blue to green by changing Ce 3+ /Tb 3+ ratio. The Ce 3+ -Tb 3+ energy transfer efficiency is determined to be 87.7% with critical distance of 12.6 Å. The application potential of LaOBr: Ce 3+ , Tb 3+ in optical thermometry was studied by exploiting the temperature sensitivity of the fluorescent intensity ratio (blue/green). It is found that fluorescent intensity ratio of LaOBr: Ce 3+ , Tb 3+ displays linear correlation with temperature in a wide range of 293–433 K with high sensitivity of 0.42% K −1 , indicating that it could be a good candidate for ratiometric optical thermometry. [ABSTRACT FROM AUTHOR]

A series of green-to-red color-tunable Sr 3 La(PO 4 ) 3 :Tb 3+ , Eu 3+ phosphors were prepared by high temperature solid-state method. The crystal structures, photoluminescence properties, fluorescence lifetimes, and energy transfer of Sr 3 La(PO 4 ) 3 :Tb 3+ , Eu 3+ were systematically investigated in detail. The obtained phosphors show both a green emission from Tb 3+ and a red emission from Eu 3+ with considerable intensity under ultraviolet (UV) excitation (~377 nm). The emission colors of the phosphors can be tuned from green (0.304, 0.589) through yellow (0.401, 0.505) and eventually to red (0.557, 0.392) due to efficient Tb 3+ -Eu 3+ energy transfer (ET). The Tb 3+ →Eu 3+ energy transfer process was demonstrated to be quadrupole-quadrupole mechanism by Inokuti-Hirayama model, with maximum ET efficiency of 86.3%. The results indicate that the Sr 3 La(PO 4 ) 3 :Tb 3+ , Eu 3+ phosphors might find potential applications in the field of lighting and displays. [ABSTRACT FROM AUTHOR]

A series of LuBO 3 : Ce 3+ /Tb 3+ /Eu 3+ phosphors were synthesized via solid state reaction. The Ce 3+ /Tb 3+ co-doped and Ce 3+ /Tb 3+ /Eu 3+ tri-doped phosphors absorb near UV light through 4 f -5 d transitions of Ce 3+ , followed by sensitized Tb 3+ green and Eu 3+ red emission. Decay curves investigations for samples with various Tb 3+ and Eu 3+ contents reveal the occurrence of Ce 3+ → Tb 3+ → Eu 3+ energy transfer. It is found that due to relative low Tb 3+ → Eu 3+ energy transfer rate, a high Tb 3+ content (>40%) is required for efficient Ce 3+ → Tb 3+ → Eu 3+ energy transfer. Emission color of LuBO 3 : Ce 3+ , Tb 3+ , Eu 3+ varies from blue through green to red with Ce 3+ /Tb 3+ /Eu 3+ ratio. The quantum efficiency of LuBO 3 : Ce 3+ , Tb 3+ green phosphor and LuBO 3 : Ce 3+ , Tb 3+ , Eu 3+ red phosphor is 50% and 30%, respectively. Green and red LED prototypes were fabricated. The results show that the obtained phosphors are potential candidates as down-converted phosphors for NUV LEDs. [ABSTRACT FROM AUTHOR]

Eu3+-activated Y(P,V)O4 phosphors were prepared by the EDTA sol-gel method, and the corresponding morphologies and luminescent properties were investigated. The sample particles were relatively spheroid with size of 2-3 &181;m and had a smooth surface. The excitation spectra for Y(P,V)O4:Eu3+ consisted of three strong excitation bands in the 200-350 nm range, which were attributed to a Eu3+-O2- charge-transfer band and ... transitions in VO43-. The as-synthesized phosphors exhibited a highly efficient red luminescence at 613 nm due to the Eu3+ 5D0 7F2 electric dipole transition. With the increase in the V5+/P5+ ratio, the luminescence intensity of the red phosphor under UV excitation was greatly improved due to enhanced VO43- energy transfer. [ABSTRACT FROM AUTHOR]3+ energy transfer. [ABSTRACT FROM AUTHOR]

A series of color-tunable NaCaBO 3 : Ce 3+ , Tb 3+ phosphors have been synthesized on the basis of efficient Ce 3+ →Tb 3+ energy transfer. The photoluminescence emission and excitation spectra, the lifetime, and the effect of Tb 3+ concentration are investigated in detail. The enhanced photoluminescence of Tb 3+ with sharp emission lines could be obtained by the broad excitation band from the allowed 4 f –5 d absorption of Ce 3+ ions. The intensity ratio of blue emission from Ce 3+ and green emission from Tb 3+ can be tuned by adjusting their concentrations. The energy transfer from Ce 3+ to Tb 3+ in NaCaBO 3 was found to be an electric dipole–quadrupole interaction. [ABSTRACT FROM AUTHOR]

Ce 3+ , Tb 3+ co-doped and Ce 3+ , Tb 3+ , Eu 3+ /Sm 3+ tri-doped La 5 Si 2 BO 13 (LSBO) were synthesized by solid-state method. Green Tb 3+ emission and red Eu 3+ /Sm 3+ emission could be efficiently sensitized by Ce 3+ . Using Tb 3+ concentration that predicted by empirical saturation distance ( R c =6–7Å), a terbium bridge is successfully formed and efficient Ce 3+ →Tb 3+ →Eu 3+ /Sm 3+ energy transfer is realized in LSBO lattice. Under UV excitation, La 5 Si 2 BO 13 : Ce 3+ , Tb 3+ , Eu 3+ /Sm 3+ system can achieve tunable emission from blue through yellowish-green to red by changing the Tb 3+ /Eu 3+ /Sm 3+ concentration. [ABSTRACT FROM AUTHOR]

A series of novel Eu 2+ /Mn 2+ co-doped color-tunable Sr 3 La(PO 4 ) 3 phosphors were synthesized by a high-temperature solid-state reaction. The photoluminescence properties and energy transfer process were investigated in detail. Two emission bands attributed to the Eu 2+ and Mn 2+ ions are observed under UV light excitation via an efficient energy transfer (ET) process. When the Eu 2+ doping content is fixed, the emission chromaticity can be varied from blue to red by simply adjusting the content of Mn 2+ . The photoluminescence and lifetime analysis indicate that there is an efficient energy transfer from the Eu 2+ to Mn 2+ ions via a quadrupole–quadrupole mechanism with the critical distance of ~10 Å. [ABSTRACT FROM AUTHOR]

A series of color-tunable Tb 3+ , Eu 3+ co-doped KCaY(PO 4 ) 2 phosphors were synthesized by solid-state reaction for the first time. The luminescent properties and energy transfer process were investigated. Cross relaxation was proved to be responsible for Tb 3+ →Eu 3+ energy transfer. The emitting color of phosphors can be tuned from green through yellow and finally to red with increasing Eu 3+ /Tb 3+ ratio. The results indicate that KCaY(PO 4 ) 2 :Tb 3+ , Eu 3+ might be served as an UV-convertible color-tunable phosphor. [ABSTRACT FROM AUTHOR]

A color-tunable Tb 3+ , Eu 3+ co-doped K 2 Y(WO 4 )(PO 4 ) phosphor was prepared by solid-state method. The excitation peak wavelength of the resulting phosphor was 377 nm and the emission peak wavelengths were at 545 nm, attributed to the 5 D 4 → 7 F 5 transition of Tb 3+ , and at 613 mm, attributed to the 5 D 0 → 7 F 2 transition of Eu 3+ . Both cross relaxation and exchange interaction are responsible for the Tb 3+ → Eu 3+ energy transfer in K 2 Y(WO 4 )(PO 4 ): Tb 3+ , Eu 3+ system. The intensity ratio of the two peaks could be freely controlled by varying the Eu/Tb ratio, allowing color to be tuned over a wide range from green to red. [ABSTRACT FROM AUTHOR]

Highlights: [•] The relationship between occupied sites and Mn2+ quantum efficiency in Mg3Ca3(PO4)4: Eu2+, Mn2+ phosphors were discussed. [•] The ion-size compensation effect leads to the formation of Eu2+–Mn2+ cluster and efficient Eu2+ →Mn2+ energy transfer. [•] Emission color can be tuned from blue to pink by adjusting Eu2+/Mn2+ ratio. [ABSTRACT FROM AUTHOR]

Abstract: A new red phosphor Ca10Na(PO4)7:Ce3+, Mn2+ was synthesized by a solid-state reaction method. Its luminescent properties were investigated by excitation/emission spectra and decay curves. Ca10Na(PO4)7:Ce3+ exhibits strong violet emission under UV excitation. For Ce3+, Mn2+ co-doped Ca10Na(PO4)7, the Mn2+ red emission is enhanced dramatically with the optimum Ce3+ co-doping. The energy transfer from Ce3+ to Mn2+ was proposed to be of resonance-type via an electric dipole–dipole mechanism, and the energy transfer efficiency was also calculated by decay data. The relationship between occupied sites and emission peak shift of Mn2+ ion in the Ca10Na(PO4)7 lattice was identified and discussed. Ca10Na(PO4)7:Ce3+, Mn2+ exhibits strong sensitized Mn2+ red emission and excellent thermal stability, which can serve as a good candidate for UV-excited red emitting phosphor. [Copyright &y& Elsevier]

A series of Ce3+, Tb3+, Eu3+ tri-doped Ba2Y( BO3)2 Cl 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)2 Cl: 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)2 Cl: Ce3+, Tb3+, Eu3+ as a novel and efficient red phosphor for NUV LED applications. [ABSTRACT FROM AUTHOR]

Highlights: [•] GdBO3: Ce3+, Tb3+, Eu3+ phosphors show blue–green–red emission under NUV excitation. [•] Energy transfer take place through Ce3+ →(Tb3+) n →Eu3+ scheme. [•] They can be used in applications for near-UV light-emitting-diodes. [ABSTRACT FROM AUTHOR]

Abstract: A series of thermal-stable Ce3+, Mn2+-codoped barium strontium lithium silicate (BSLS) phosphors was synthesized by a high-temperature solid-state reaction. The XRD patterns of this phosphor seem to be a new phase that has not been reported before. BSLS:Ce3+, Mn2+ showed two emission bands under 365nm excitation: one observed at 421nm was attributed to Ce3+ emission, and the other found in red region was assigned to Mn2+ emission through Ce3 +–Mn2+ efficient energy transfer. The Mn2+ emission shifted red along with the replacement of barium by strontium, which was due to the change of crystal field. A composition-optimized phosphor, BSLS:0.10Ce3+, 0.05Mn2+ (Ba=65), exhibited strong and broad red-emitting and supreme thermal stability. The results suggest that this phosphor is suitable as a red component for NUV LED or high pressure Hg vapor (HPMV) lamp. [ABSTRACT FROM AUTHOR]

Abstract: Akermanite phosphor Sr2MgSi2O7:Eu2+ was synthesized by solid-state reaction under a H2–N2 atmosphere, and its photo-physical behaviors were systematically characterized by photoluminescence excitation and emission spectra, concentration quenching, and thermal quenching process. This phosphor is efficiently excited in the wavelength range of 300–420nm, which matches to a near UV-emitting InGaN chip, and emits strong and wide band blue light peaking at 470nm. The relationship between emission peak wavelength and Eu2+ occupied sites was illuminated through Van Uitert''s equation. The concentration quenching mechanism was verified to be a dipole–dipole interaction and the critical energy-transfer distance was confirmed as around 13Å through both calculated crystal structure method and experimental spectral method. The activation energy for thermal quenching was calculated to be 0.4044eV. Phosphor-converted LED was fabricated with Sr2MgSi2O7:0.06Eu2+ and 395nm-emitting InGaN chip and exhibited strong wide band blue emission. These results indicate that Sr2MgSi2O7:Eu2+ is a promising candidate as a blue component for near UV-based multi-phosphor-converted white LEDs. [Copyright &y& Elsevier]

Thermally stable narrow-band green phosphor is important for phosphor-converted light emitting diodes (pc-LEDs). Herein, an efficient and stable Na 2 MgAl 10 O 17 : Eu2+, Mn2+ green phosphor is obtained using Eu2+-Mn2+ energy transfer strategy. The Mn2+ activator could be effectively sensitized by the addition of Eu2+ with significant UV absorption enhancement, then generates a bright green emission with peak at 515 nm and FWHM of 40 nm. The internal and external quantum efficiencies of optimal phosphor Na 2 MgAl 10 O 17 : 0.15Eu2+, 0.50Mn2+ are measured as 69.5 and 30.8 %, respectively. It is found that Na 2 MgAl 10 O 17 : Eu2+, Mn2+ phosphor shows good chemical and thermal stability, i.e. maintains no quenching after H 2 O/HCl soaking and keeps 90 % of RT intensity at 200 °C. By using Na 2 MgAl 10 O 17 : Eu2+, Mn2+ as converted phosphor, single-chromatic and white pc-LEDs were fabricated, which simultaneously achieve green and white emission with high brightness. Our results show that this Na 2 MgAl 10 O 17 : Eu2+, Mn2+ is a potential candidate as a thermally stable green phosphor for white LEDs. [ABSTRACT FROM AUTHOR]

New dual-emitting phosphor Na 2 BaMg(PO 4) 2 : Eu2+, Mn2+ is prepared via conventional sintering method. The structural and luminescent properties of as-synthesized phosphor were systematically studied by experimental characterization and theoretical calculation. Utilizing the Eu2+→Mn2+ energy transfer, this phosphor exhibits efficient double-band emissions at 415 and 620 nm, which has a good match with the absorption spectra of chlorophyll A/B and phytochrome in plants. The energy transfer mechanism had been investigated through emission intensity and decay lifetime variation using Reisfeld's approximation method. Na 2 BaMg(PO 4) 2 : Eu2+, Mn2+ shows promising properties like good thermal stability (75% emission intensity maintenance at 200 °C) and high quantum efficiency (QE > 80%). A prototype LED was fabricated using optimized phosphor and NUV chip, which exhibits two distinct emission peaks modulating an optimum action spectrum for plant absorption. All results indicate that Na 2 BaMg(PO 4) 2 : Eu2+, Mn2+ is of great potential as converted component for plant growth LEDs. [ABSTRACT FROM AUTHOR]

Stable and efficient broadband near-infrared (NIR) emitting phosphors are vital for the next-generation NIR sources. However, it still remains challenging to construct such phosphors, particularly those with a NIR-II window. In this work, using the Cr3+-Yb3+ energy transfer (ET) strategy, the as-synthesized Ca 2 ScTaO 6 :Cr3+, Yb3+ phosphor retains 86.2% of the initial luminescence intensity of Yb3+ at 373 K with characteristic emissions of both activators ranging from 700 nm to 1200 nm. The occupation of Cr3+ into both Ta5+ and Sc3+ sites is confirmed by X-ray diffraction, time-resolved emission spectrum, and crystal structure. The efficient ET from Cr3+ to Yb3+ is revealed by the diffuse reflection spectrum, steady-state and transient fluorescence. As a result, it contributes to the excellent performance of the phosphor. Based on the optimized phosphor, a NIR light-emitting diode is fabricated and demonstrated its advantage in imaging and potential application in information encryption. The result highlights ET as a robust strategy to construct efficient NIR phosphor. [ABSTRACT FROM AUTHOR]

The exploration of efficient and high-purity red phosphors is an urgent need in LED development. Due to the compact and compositional-tunable structure of whitlockite compound, manganese-based Ca 19 Mn 2 (PO 4) 14 is chosen as phosphor host for Eu2+ sensitization. Rietveld refinement, steady-state spectra, decay lifetime analysis and temperature-dependent emission spectra were investigated and clearly discussed. Under 360 nm excitation, Ca 19 Mn 2 (PO 4) 14 : Eu2+ shows a strong Mn2+ sensitized emission at 655 nm with FWHM of 82 nm, benefiting from the short-distance-induced high-efficient Eu2 -Mn2+ energy transfer. Emission engineering of Ca 19 Mn 2 (PO 4) 14 : Eu2+ is achieved by Sr2+ co-doping, leading to both tunable peak wavelength (ranging from 650 to 610 nm) and improved intensity (130% of original value). Moreover, Ca 19 Mn 2 (PO 4) 14 : Eu2+ exhibits a promising thermal stability where only 40% of emission intensity is lost at 200 °C. Finally, we explored the working performance of the fabricated RGB phosphor-converted white LED. The present work indicates that Ca 19 Mn 2 (PO 4) 14 : Eu2+ phosphor is of great potential as a promising and efficient red phosphor in phosphor-converted white LED. [ABSTRACT FROM AUTHOR]

Abstract: A novel yellow-emitting phosphor NaCaPO4:Tb3+,Eu3+ was synthesized using a conventional, solid-state reaction for solid-state lighting applications. The luminescence properties supported the occurrence of energy transfer from Tb3+ to Eu3+ ions. The energy transfer mechanism was studied and demonstrated to be a quadrupole–quadrupole interaction. The decay curves of NaCaPO4:0.04Tb3+,xEu3+ phosphors further confirmed the existence of energy transfer from Tb3+ to Eu3+ ions. This energy transfer induced a change in the emitted color of the phosphors from green to yellow, which can be obtained by appropriately tuning the Eu3+ concentration. The results indicated that NaCaPO4:Tb3+,Eu3+ provided a clue for the search of phosphors for white-light-emitting diodes. [Copyright &y& Elsevier]

Abstract: An intense green phosphor, LiSrPO4:Eu2+, Tb3+, was synthesized by high temperature solid-state reaction. The photoluminescence excitation and emission spectra, the lifetime and concentration effect are investigated in detail. The results show that an efficient non-radiative energy transfer from Eu2+ to Tb3+ occurs and its efficiency is about 66.4%. Tb3+ ions give an intense green emitting light by a strong excitation band of Eu2+ ions at 280–410nm, matching well with the dominant emission band of (n)-UV (350–420nm) LEDs. A phosphor-converted green LED was fabricated by coating the LiSrPO4:Eu2+, Tb3+ phosphor onto (n)-UV chip emitting at 370nm. These results demonstrate that Tb3+ ion with low 4f–4f absorption efficiency in (n)-UV region can play a role of activator in narrow green-emitting phosphor potentially useful in (n)-UV GaN-based LED through efficient energy feeding by allowed 4f–5d absorption of Eu2+ with high oscillator strength. [Copyright &y& Elsevier]

A high-purity green-emitting Sr 2 (Mg,Mn)Al 22 O 36 solid-solution phosphor and its partial doped compound (Sr 2 (Mg,Mn)Al 22 O 36 : Eu2+) were synthesized via solid-state reaction. This solid-solution phosphor shows a green band at 518 nm from Mn2+ instinct 4 T 1 -6 A 1 transition with a narrow FWHM of 28 nm. This green emission is of high color purity (87.7%) and thermal stable (80% of original intensity at 473 K). However, the emission intensity requires further enhancement due to the limitation of Mn2+ 3 d -3 d forbidden transition. With a tiny amount of Eu2+ introduced into Sr 2 (Mg,Mn)Al 22 O 36 , the luminescence intensity enormously improved to 260% of that in blank sample due to high-efficient Eu2+-Mn2+ energy transfer, which is induced by a structural confinement effect with Eu2+-Mn2+ distance of 6.225 Å. Thus, the EQE of optimal phosphor Sr 2 Mg 0 · 2 Mn 0 · 8 Al 22 O 36 : 0.01Eu2+ is boosted to 42%. The above results hint that Sr 2 (Mg,Mn)Al 22 O 36 : Eu2+ has promising application potential as a green phosphor for backlighting LEDs in wide-color-gamut display, and this sensitized strategy could be applied for the development of high-performance phosphors. [ABSTRACT FROM AUTHOR]

Eu3+-activated Sr 9 LiMg(PO 4) 7 phosphors, which presented bright red emissions mainly from the 5 D 0 →7 F 2 transition of Eu3+ ions upon the near-ultraviolet excitation, were successfully synthesized in ambient atmosphere. The crystal structure, phase constitution, photoluminescent behaviors, decay time, internal quantum efficiency and thermal stability of the resultant phosphors were investigated in detail. Eu3+ ions are found to tend to occupy multiple Sr2+ sites, which are 7, 8 and 10-coordinated. The optimal doping concentration is 7 mol% and the electrical multipolar interaction contributed to the non-radiative energy transfer between Eu3+ ions in Sr 9 LiMg(PO 4) 7 host lattices. Temperature-dependent PL spectra indicated Sr 9 LiMg(PO 4) 7 : Eu3+ possess excellent emission and color stability at elevated temperature. Fabricated single-chromatic LED prototype emit bright red light under 20 mA bias current, which demonstrates that Sr 9 LiMg(PO 4) 7 : Eu3+ phosphor is of great potential as converted phosphor in NUV LED application. [ABSTRACT FROM AUTHOR]

Abstract A series of emission color tunable Ce3+, Tb3+, and Eu3+ co-doped La 2 Si 2 O 7 (LSO) phosphors have been prepared via a solid state reaction. The crystal structure, luminescence properties, and thermal stability of the phosphors were studied in this paper. There exists two kinds of energy transfer (ET) modes under UV excitation, namely, electric dipole-dipole interaction for Ce3+→Tb3+ and terbium bridge model [Ce3+→(Tb3+) n →Eu3+] for LSO:Ce3+,Tb3+,Eu3+ system. The emitting color of the phosphors can be tuned from green to yellow and eventually to orange-red through the Ce3+→Tb3+→Eu3+ energy transfer. Although codoping Tb3+ and Eu3+ into La 2 Si 2 O 7 :Ce3+ leads to the reduction of thermal stability, it still remains 80% for LSO:0.05Ce3+,0.8 Tb3+,0.02Eu3+ at 150 °C when compared to that at room temperature. The absolute quantum yield (QY) increases from 71.04% (LSO:0.05Ce3+) to 95.60% (LSO:0.05Ce3+, 0.6 Tb3+), while those of LSO:0.05Ce3+, y Tb3+,0.02Eu3+ samples remain more than 70%. These results indicate that the phosphors can be candidates for application in phosphor-converted white light-emitting diodes (pc-WLEDs). Graphical abstract Image 1 Highlights • La 2 Si 2 O 7 :Ce3+,Tb3+,Eu3+ has been prepared by a high-temperature solid state reaction. • The emitting color can be tuned from green to yellow and then to orange-red. • [Ce3+→(Tb3+) n →Eu3+] bridge is responsible for the enhancement of Eu3+ emission. • The quantum efficiency of 0.05Ce3+, y Tb3+,0.02Eu3+ codoped samples is more than 70%. • The phosphors exhibit good thermal stability. [ABSTRACT FROM AUTHOR]

Abstract High-efficient Ce3+/Tb3+ co-doped Ba 3 Y 2 B 6 O 15 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 Ba 3 Y 2 B 6 O 15 : 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 (T 50 = ~ 120 °C). The results indicate that these efficient color-tuning Ba 3 Y 2 B 6 O 15 : Ce3+, Tb3+ might be candidate as converted phosphor for UV-excited light-emitting diodes. [ABSTRACT FROM AUTHOR]

Bi 3+ and Sm 3+ co-doped with Li 3 Ba 2 Gd 2.95− y Eu 0.05 (MoO 4 ) 8 red phosphors were synthesized by a solid-state reaction. The phosphors were characterized by X-ray powder diffraction, field-emission scanning electron microscopy, and photoluminescence spectroscopy analyses. The 5 D 0 → 7 F 2 transition of Eu 3+ that led to the red emission of the phosphors was predominantly observed in the photoluminescence spectra. The enhanced emission intensity at 616 nm demonstrated efficient energy transfer from Bi 3+ or Sm 3+ ions to Eu 3+ ions. The high color purities of Li 3 Ba 2 Gd 2.92 Eu 0.05 Bi 0.03 (MoO 4 ) 8 and Li 3 Ba 2 Gd 2.945 Eu 0.05 Sm 0.005 (MoO 4 ) 8 phosphors were calculated at 94.8% and 95.1%, respectively. Results indicated that Li 3 Ba 2 Gd 2.92 Eu 0.05 Bi 0.03 (MoO 4 ) 8 and Li 3 Ba 2 Gd 2.945 Eu 0.05 Sm 0.005 (MoO 4 ) 8 red phosphors can be used for white light-emitting diodes. [ABSTRACT FROM AUTHOR]

Dual-emitting alkaline silicate phosphors Na 2 Mg 2 Si 6 O 15 : Eu2+, Mn2+ have been synthesized to realize blue and red emissions to boost photosynthesis process. At UV excitation, Na 2 Mg 2 Si 6 O 15 : Eu2+, Mn2+ phosphors exhibit efficient blue and red emissions due to Eu2+ 4 f -5 d transition and Mn2+ 3 d -3 d transition, which matches well with the absorption of plant chlorophylls, and also could be excited by near ultraviolet LED chip. The emitting color could be readily tuned from blue through pink to red due to effective Eu2+-Mn2+ energy transfer by changing Eu2+/Mn2+ ratio. And the corresponding energy transfer mechanism is found to be dipole-dipole interaction. The thermal stability of Na 2 Mg 2 Si 6 O 15 : Eu2+, Mn2+ is significantly higher than that of most reported Eu2+, Mn2+ co-activated dual-emitting phosphors, due to thermally activated defect-Eu2+-Mn2+ energy transfer process. Thus, it indicates that Na 2 Mg 2 Si 6 O 15 : Eu2+, Mn2+ is of great potential as converted phosphors for plant growth application. [Display omitted] • Novel Na 2 Mg 2 Si 6 O 15 : Eu2+, Mn2+ phosphors with controllable emission was synthesized. • Phosphor shows efficient blue (400–500 nm) and red (600–700 nm) double-band light under NUV excitation. • The energy transfer efficiency and the energy transfer mechanism were investigated. • Efficient and stable blue-red emission in Na 2 Mg 2 Si 6 O 15 : Eu2+, Mn2+ promote application in plant growth LED. [ABSTRACT FROM AUTHOR]

Different crystallographic sites occupation has significant influence on the luminescent characteristics of the Eu2+ and Mn2+ activated phosphors. In this study, in order to have an in-depth research on basic photoluminescence mechanism, a compositional modification for luminescent tuning and enhancement in whitlockite-structural phosphor Sr 19 (Mg 1- x Mn x) 2 (PO 4) 14 : Eu2+ is applied. The result shows that both Eu2+/Mn2+ site-occupancy and Eu2+-Mn2+ energy transfer could be tuned by changing Eu2+/Mn2+ content in Sr 19 (Mg 1- x Mn x) 2 (PO 4) 14. Owing to this, the emission variation from Eu2+ orange through Mn2+ red to double blue-red bands is simultaneously observed upon ultraviolet light excitation. Meanwhile, the optical spectroscopy property, decay and thermal quenching behavior as well as related mechanism of optimal Sr 19 (Mg 1- x Mn x) 2 (PO 4) 14 : Eu2+ are studied in detail. • Whitlockite-structural phosphor Sr 19 (Mg/Mn) 2 (PO 4) 14 : Eu2+ was synthesized. • Both Eu2+/Mn2+ site-occupancy and Eu2+-Mn2+ energy transfer could be tuned by composition modification. • Emission variation from Eu2+ orange through Mn2+ red to double blue-red bands is simultaneously observed. [ABSTRACT FROM AUTHOR]

• Structure, site-occupancy and luminescence of Na 3 SrMg 11 (PO 4) 9 :Eu2+/Mn2+/Tb3+ were studied. • Broad excitation band and wide-gamut-coverage emission could be achieved by tuning Eu2+/Mn2+/Tb3+ ratio. • The optimal blue/green/red phosphors exhibit high quantum efficiencies with IQE>60%. [Display omitted] A series of tricolor-emitting fifillowite-structured Eu2+/Tb3+/Mn2+-doped Na 3 SrMg 11 (PO 4) 9 (NSMP) phosphors were synthesized. Its structural parameter, luminescent properties, and energy transfer behaviors were systematically studied. The optimal NSMP: Eu2+, Tb3+/Mn2+ phosphors exhibit bright RGB emission bands, i.e. blue emission from Eu2+, while green and red emission from sensitized Tb3+ and Mn2+, respectively. Eu2+-Tb3+/Mn2+ energy transfer processes are verified as a resonant type with ET efficiency of>80%. The emitting colors of NSMP: Eu2+, Tb3+, Mn2+ phosphors could be adjusted from blue (0.156, 0.077) to green (0.322, 0.552), to red (0.667, 0.299) by increasing Tb3+/Mn2+ doping content. The internal quantum efficiency of blue NSMP:0.04Eu2+, green NSMP:0.04Eu2+, 0.40Tb3+ and red NSMP:0.04Eu2+, 1.40Mn2+ phosphor is estimated at 64.46%, 78.17% and 78.03%, respectively. A significant leap of emission thermal-stability is found in Na 3 SrMg 11 (PO 4) 9 : Eu2+ after co-activation with Mn2+/Tb3+ ions. In general, the emitting colors and energy transfer could be effectively regulated in the Na 3 SrMg 11 (PO 4) 9 host, and a general method for photoluminescence tuning is demonstrated. [ABSTRACT FROM AUTHOR]

The Ce3+/Tb3+/Mn2+ activated color-tunable phosphors Sr 9 LiMg(PO 4) 7 (SLMP) were prepared by solid-state reaction with post-annealing treatment. The structural, static and time-resolved luminescent properties are studied in detail. XRD pattern showed the pure trigonal phase of Sr 9 LiMg(PO 4) 7 at an annealing temperature of 1300 °C. Ce3+-doped SLMP phosphor exhibits near-ultraviolet emission with peak-wavelength at 380 nm. Efficient Ce3+-Tb3+/Mn2+ energy transfer process is demonstrated by luminescence spectrum and luminescence lifetimes of as-prepared samples. The emitting-color of SLMP: Ce3+/Tb3+/Mn2+ was tunable through changing Ce3+/Tb3+/Mn2+ ratio. Emission peak intensity of SLMP: Ce3+, Tb3+ phosphor shows good thermal stability with rising temperature. These results suggest its great potential as luminescent materials with good performance for UV-excitable applications. Unlabelled Image • Tunable-emission was gained in the Sr 9 LiMg(PO 4) 7 : Ce3+/Tb3+/Mn2+ phosphor. • The energy transfer from Ce3+ and Tb3+/Mn2+ was observed and verified. • High thermal stability was obtained in Ce3+-Tb3+ co-doped phosphors. • Sr 9 LiMg(PO 4) 7 : Ce3+/Tb3+/Mn2+ could have potential in UV-excitable applications. [ABSTRACT FROM AUTHOR]

A series of dual-emitting Eu2+, Mn2+ co-doped Ca 19 Zn 2 (PO 4) 14 (CZP) phosphors capable for plant cultivation LEDs are synthesized. As a sensitzer, Ca 19 Zn 2 (PO 4) 14 : Eu2+ emits a dominant blue light with green shoulder by Eu2+ occupying CaO 8 and CaO 6 sites, respectively. Mn2+ was introduced into CZP: Eu2+ to obtain the red emission component. The as-synthesized CZP: Eu2+, Mn2+ phosphor shows a blue emission peaking at 415 nm and significantly enhanced deep-red emission peaking at 650 nm under single UV excitation, which should be attributed to the existence and energy transfer of Eu2+ and Mn2+, respectively. The emission spectra match well with the plants' photosynthetic action spectra (PAS) for both red and blue lights simultaneously. Energy transfer from Eu2+ to Mn2+ enables a facile tune of emitting color from blue to red, and the corresponding mechanism is revealed to be the electric dipole-dipole interaction by analyzing Eu2+/Mn2+ decay lifetime variations. High quantum efficiency (93.3%) and favorable thermal stability (68% of RT intensity at 473 K) clearly verify the good properties of CZP: Eu2+, Mn2+ phosphor. Results confirmed that CZP: Eu2+, Mn2+ phosphor might have great applicational potential in plant growth LED lighting. Novel dual-emitting phosphors Ca 19 Zn 2 (PO 4) 14 : Eu2+, Mn2+ are synthesized by solid-state reaction. Eu2+ and Mn2+ is found to be located in Ca2+ and Zn2+ site of host lattice. Samples exhibit high quantum efficiency (93.3%) and good thermal stability (68% of RT intensity at 473 K), which is a promising phosphors for plant-cultivation LEDs. Image 1 • Ca 19 Zn 2 (PO 4) 14 : Eu2+, Mn2+ dual-emitting phosphors were synthesized for the first time. • Blue-red dual emission can be effectively excited by UV and match well with plants' photosynthetic action spectra. • Energy transfer from Eu2+ to Mn2+ was studied by emission and lifetime variations. • Phosphors exhibit high quantum efficiency (93.3%) and good thermal stability (68% of RT intensity at 473 K). [ABSTRACT FROM AUTHOR]