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An ever increasing demand for white light‐emitting diodes (W‐LEDs) results in the gradual growth of research on functionalized luminescent glasses. In this paper, single‐composition tunable white‐emitting Eu2+‐Tb3+‐Eu3+ tri‐activated glasses were synthesized by melt quenching method without additional reducing atmosphere. The coexistence of Eu2+ and Eu3+ was confirmed by ultraviolet‐visible transmission spectra, photoluminescent spectra, fluorescence decay curves, and X‐ray photoelectron spectroscopy. Tb3+ can act as bridge to connect Eu2+‐Eu3+ luminescent centers by energy transfer. Tone‐tunable white light can be achieved by coupling the emission centered at 412, 541, and 612 nm contributed from Eu2+, Tb3+, and Eu3+, respectively. By adjusting the relative content of Eu2+/Tb3+/Eu3+, ideal chromaticity coordinates of (0.33, 0.33) can be achieved under excitation of ultraviolet light. High thermal stability and tiny chromaticity shift were exhibited in samples. These results suggest that Eu2+‐Tb3+‐Eu3+ tri‐activated glasses have great potential application in ultraviolet‐driven W‐LEDs. [ABSTRACT FROM AUTHOR]

Single‐composition Ba2Y2Si4O13:Bi3+,Eu3+ (BYSO:Bi3+,Eu3+) phosphors with color‐tunable and white emission were prepared by conventional high temperature solid‐state reaction method. The structural and luminescent properties of these phosphors were thoroughly investigated through X‐ray diffraction, photoluminescence, and decay curves. BYSO:Bi3+ phosphors show two excitation peaks at 342 and 373 nm, and give two emission peaks at 414 and 503 nm, respectively, indicating that there are two sites of Bi3+ in BYSO. The energy transfer from Bi3+ to Eu3+ was investigated in detail. Varied hues from blue (chromaticity coordinate [0.219, 0.350]) to white (0.288, 0.350) and orange‐red light (0.644, 0.341) can be generated by adjusting the content of Eu3+. Pure white light emission (0.311, 0.338) can be obtained under the excitation of 355 nm in BYSO:3%Bi3+,20%Eu3+ phosphor. Besides, BYSO:Bi3+,Eu3+ phosphors exhibit distinct thermal quenching properties, whose emission intensity at 473 K is 82.6% of that at 298 K. Our results indicate that BYSO:Bi3+,Eu3+ may be applied as conversion phosphors for n‐UV‐based W‐LEDs. [ABSTRACT FROM AUTHOR]

Abstract Novel single-phased phosphors SrY 2 O 4 :Bi3+,Eu3+ (SYO:Bi3+,Eu3+) with tunable emitting were successfully synthesized by the conventional solid-state method. X-ray diffraction, excitation and emission spectra, decay curves as well as temperature-dependent luminescence were applied to characterize the as-obtained phosphors. Under ultraviolet (UV) excitation, blue luminescence centered at 410 nm was found in SYO:Bi3+. By introducing Eu3+ into SYO:Bi3+, highly efficient energy transfer (ET) process with ET efficiency of 92.65% from Bi3+ to Eu3+ was obtained before concentration quenching. The possible ET mechanism from Bi3+ to Eu3+ were investigated systematically. By altering Eu3+ content, tunable emission from blue to red was realized. More importantly, investigation of the thermal stability showed that over 98% of the room-temperature emission intensity was still preserved at 155 °C, which is superior to that of most recently reported Bi3+,Eu3+ co-doped phosphors. These results indicate that this kind of easy fabrication, low-cost and highly stable SYO:Bi3+,Eu3+ are potential candidates for blue-red phosphors for application in UV chip based w-LEDs. Highlights • Novel phosphors SrY 2 O 4 :Bi3+,Eu3+ with tunable emitting from blue to red were synthesized. • Highly efficient energy transfer (ET) from Bi3+ to Eu3+ was obtained before concentration quenching. • Excellent thermal stability was determined, which is superior to that of most recently reported Bi3+,Eu3+ co-doped phosphors. [ABSTRACT FROM AUTHOR]

A novel single-phased tunable emitting phosphor Ba 9 Lu 2 Si 6 O 24 :Bi 3+ ,Eu 3+ (BLSO:Bi 3+ ,Eu 3+ ) was successfully prepared via a simple solid-state approach. The main excitation peaks range from 320 to 400 nm of BLSO:Bi 3+ were identified by photoluminescence characterization, indicating BLSO:Bi 3+ viable for ultraviolet (UV) excitation. Emission spectra show that Bi 3+ occupies at least two nonequivalent sites in BLSO host, and display broad emission peaks at 410 and 490 nm when excited by UV light, respectively. As red emitting center Eu 3+ was introduced into BLSO:Bi 3+ , significant energy transfer (ET) occurs from Bi 3+ to Eu 3+ through a dipole-dipole mechanism. The ET efficiency reaches 97.57%. By varying the doped ratio of Bi 3+ and Eu 3+ , tunable light and white emission can be easily realized. Results indicate that BLSO:Bi 3+ ,Eu 3+ is a potential tunable emission phosphor in UV excited W-LEDs. [ABSTRACT FROM AUTHOR]

Thermal quenching is one of the most key challenges of ultraviolet converted white light-emitting diodes (UV converted WLEDs) when they operate at high driving current, in which the phosphors are subjected to the luminescence losses resulting from non-radiative transitions with augmenting temperature. Herein, novel single-phased Bi3+,Sm3+-doped SrY 2 O 4 (SYO) phosphors with abnormal thermal quenching property were successfully prepared applying a high-temperature solid-state strategy. X-ray diffraction, luminescent behaviors, lifetimes and temperature-dependent emission properties were employed to study the obtained powder materials. Under UV light irradiation, tunable emission from blue to red based on the energy transfer (ET) from Bi3+ to Sm3+ via a dipole-dipole mechanism is realized. Significantly, the obtained phosphors do not display thermal quenching even up to 573 K (300 °C). And they exhibit tiny chromaticity shift even at high temperature, indicative of excellent color stability. These phenomena may be interpreted by the ET from defect levels to Bi3+ excited states, which was identified by thermoluminescence measurements. These results indicate potential applications of SYO:Bi3+,Sm3+ in UV converted WLEDs. • Tunable emissions from blue to red light were realized. • Efficient energy transfer from Bi3+ to Sm3+ was detected. • Abnormal anti-thermal quenching property and superior color stability were found. • SrY 2 O 4 :Bi3+,Sm3+ are of great potential utilizations in UV converted WLEDs. [ABSTRACT FROM AUTHOR]

Highly transparent Ce3+, Tb3+ co-doped sodium silicate glasses were prepared by melt-quenching technique. The luminescent properties of Ce3+, Tb3+ single-doped and co-doped glasses, energy transfer process from Ce3+ to Tb3+ were systemically investigated through excitation spectra, emission spectra, decay curves, and energy level diagram. Tuning the content of Tb3+ can generate the varied hues from blue to white and eventually to yellowish green. Our results suggest that Ce3+, Tb3+ co-doped sodium silicate glasses could be used as converting phosphors for Near-ultraviolet LED chips to generate W-LEDs. [ABSTRACT FROM AUTHOR]

White light-emitting diodes (W-LEDs) occupy an important role in human life. The lack of red-light emission phosphors makes the packaged W-LEDs have high color temperature and low color rendering index. Herein, Bi3+ and Eu3+ doped Lu 2 WO 6 phosphors with red luminescence were manufactured. The structural properties, luminescent properties and energy transfer processes were investigated systemically. Under ultraviolet light stimulation, blue, green and red light emissions are detected, which stem from (WO 6)6-, Bi3+ and Eu3+, respectively. Significantly, the optimal sample of Lu 2 WO 6 :0.002Bi3+,0.18Eu3+ presents favorable thermal stability, whose luminescent intensity at 423 K keeps 94% of that at 300 K. Above results unlock that Lu 2 WO 6 :Bi3+,Eu3+ samples might have promising application in solid-state lighting field. [ABSTRACT FROM AUTHOR]

Contactless optical thermometers have attracted extensive attentions for applications in scientific research and technological fields due to their apparent advantages. Herein, a novel sequence of Ba 3-x Sr x Lu 4 O 9 (B 3-x S x LO):Er3+/Yb3+ phosphors were successfully prepared to investigate the temperature sensing property. By establishing energy transfer from Yb3+ to Er3+ and regulating the local lattice environment, up-conversion luminescence of Er3+ is dramatically improved when excited by 980 nm laser. This can effectively promote signal-noise ratio and reduce the errors in temperature detection. Furthermore, a multi-mode optical thermometry, which includes the fluorescence intensity ratio (FIR) from two thermally coupled levels of 2H 11/2 /4S 3/2 , FIR based on non-thermally coupled system of 2H 11/2 /4F 9/2 and fluorescence lifetime of 4S 3/2 state of Er3+, was explored systematically. The fabricated samples exhibit the superior temperature measurement performances containing wide temperature-sensing range, superior signal discriminability, high sensitivity and favorable repeatability, indicative of the enormous utilization prospects of B 3-x S x LO:Er3+/Yb3+ for thermometry. [ABSTRACT FROM AUTHOR]

Improved up-conversion (UC) luminescence and applications in optical temperature sensors of up-converting materials have attracted growing interest in recent years. Here, we reported a new series of Ba 3-x Sr x Lu 4 O 9 (B 3-x S x LO):Tm3+/Yb3+ phosphors. By designing Yb3+→Tm3+ energy transfer and modifying the local lattice environment of activator ions via cationic substitution, highly efficient enhancement of UC luminescence of Tm3+ is realized when excited by a 980 nm laser. Moreover, the representative B 2.2 S 0.8 LO:Tm3+/Yb3+ sample displays superior temperature sensing behaviors with highly relative sensitivity of 0.88 % at 428 K, absolute sensitivity of 1.50 % at 573 K, wide sensing range and good stability. All of findings reveal that B 3-x S x LO:Tm3+/Yb3+ are promising candidates for optical thermometry. [ABSTRACT FROM AUTHOR]

Herein, a series of novel Na 2 GdMg 2 (VO 4) 3 :Eu3+ (NGMVO:Eu3+) red phosphors were elaborated by conventional solid-state reaction process. Their structural features, luminescent properties, energy transfer were researched at length. XRD patterns indicate that NGMVO:Eu3+ crystallized in single cubic garnet structure. Under the excitation of near ultraviolet light at 356 nm, the emission spectra of NGMVO host could be divided in two parts that resulted from 3T 2 → 1A 1 and 3T 1 → 1A 1 transitions of VO 4 3−. While NGMVO:Eu3+ phosphors show intense sharp red emission peaks including 590, 610, 652 and 706 nm that originated from 5D 0 → 7F J (J = 1–4) transitions of Eu3+, respectively. The optimal concentration of Eu3+ is 0.7. Importantly, NGMVO:0.7Eu3+ sample presents high energy transfer efficiency (89 %) and high external quantum efficiency (48.3 %). Besides, its emission intensity remains 79 % at 420 K compared with that at 300 K, proving the good thermal stability of phosphors. All above results suggest that NGMVO:Eu3+ red phosphors have latent applications in white light emitting diodes. [ABSTRACT FROM AUTHOR]

A new type of Bi3+,Eu3+ single- and co-doped Na 3.6 Y 1.8 (PO 4) 3 phosphate phosphors were manufactured using conventional high-temperature solid-state reaction technique to explore their application for solid-state lighting. The crystal structure, luminescent properties, luminescent mechanism and quantum efficiency were thoroughly explored. Results show that there are two crystallization sites for Bi3+ and Eu3+ ions. Upon the excitation of 342 and 373 nm, Bi3+ single-doped phosphors exhibit green and blue emission, derived from the 3P 1 to 1S 0 transition of Bi3+ located in different occupancy sites. Thanks to radiative energy transfer process from Bi3+ to Eu3+, adjustable emission could be acquired by altering Eu3+ content in co-doped phosphors. Pure white-light emission with quantum efficiency value of 22.9% can be realized in Na 3.6 Y 1.8 (PO 4) 3 :0.01Bi3+,0.1Eu3+ sample and the integrated intensity of white light emission at 417 K remains 85% of that at room temperature. Our results indicate that Na 3.6 Y 1.8 (PO 4) 3 :Bi3+,Eu3+ phosphors have feasible application in high-power ultraviolet driven solid-state lighting. [ABSTRACT FROM AUTHOR]

Bi3+/Eu3+-doped SiO 2 –Al 2 O 3 –CaO–B 2 O 3 –La 2 O 3 –K 2 O glasses were fabricated and the luminescent properties, energy transfer as well as thermal stability were systematically investigated. Under 333 nm light excitation, bluish-green luminescence centered at 480 nm is observed in the obtained Bi3+-doped glass. By co-doped with Eu3+, highly efficient energy transfer process happens from Bi3+ to Eu3+ via a quadrupole-quadrupole interaction. The energy transfer efficiency can reach 86% and the concentration of Eu3+ is not quenched in here. With increasing Eu3+ concentration, tunable luminescence from bluish-green via white to orange-red is realized. Significantly, pure white light emission with CIE coordinates (0.348, 0.333) is obtained when excited by 333 nm light. Temperature-dependent emission spectra present superior color stability in operating temperature lower than 423 K for the prepared glasses. These results indicate that these glasses are potential white light emitting materials for organic-resin-free W-LEDs. • Bi3+/Eu3+ single and co-doped SiAlCaBLaK oxide glasses were fabricated. • Emission, excitation and lifetime prove the energy transfer from Bi3+ to Eu3+. • Bi3+/Eu3+ doped glasses can act as white-light material for W-LED. [ABSTRACT FROM AUTHOR]

Ca 2 YZr 2 Al 3 O 12 :Bi3+,Eu3+ phosphors were elaborated by a traditional solid-state reaction method. The luminescence of Ca 2 YZr 2 Al 3 O 12 :Bi3+ samples, energy transfer from Bi3+ to Eu3+, and the temperature sensing properties of Ca 2 YZr 2 Al 3 O 12 :Bi3+,Eu3+ samples have been systematically researched. Under the excitation of ultraviolet light, Bi3+ single doped phosphors give 313 and 392 nm emission bands, which origin from the substitutions of Bi3+ instead of Ca2+ and Y3+ sites, respectively. And the color-adjustable emission from blue to red were observed by increasing Eu3+ content in Ca 2 YZr 2 Al 3 O 12 :Bi3+,Eu3+ samples. Relying on different temperature dependent variation tendency, the fluorescence intensity ratio (FIR) values present outstanding temperature sensing properties. The absolute and relative sensitivity can be up to 0.826 %K-1 and 0.664 %K-1, respectively. All above results suggest that Ca 2 YZr 2 Al 3 O 12 :Bi3+,Eu3+ phosphor is a potential alternative for optical thermometer. [ABSTRACT FROM AUTHOR]

In this paper, a series of Bi3+ and Eu3+ single-doped as well as Bi3+,Eu3+ co-doped Ba 9 Y 2 Si 6 O 24 samples were synthesized through a simple high-temperature solid-state reaction method. Their crystal structures, morphologies, luminescent properties, temperature-dependent emission spectra, decay curves and quantum efficiencies were investigated in detail. Upon ultraviolet light excitation, Bi3+ single-doped samples exhibited blue and green emissions peaking at 408 and 501 nm, corresponding to the 3P 1 –1S 0 transition of Bi3+ ions. The spectral analysis indicated that there were two different luminescent centers of Bi3+ ions due to different occupancies in Ba 9 Y 2 Si 6 O 24 host lattice. And the highest quantum efficiency can reach 64.5% in Ba 9 Y 2 Si 6 O 24 :0.024Bi3+ phosphor. The remarkable spectral overlap between the emission spectra of Bi3+ ions and the excitation spectra of Eu3+ ions indicated the exist of energy transfer from Bi3+ to Eu3+. The efficient energy transfer from Bi3+ to Eu3+ has been investigated in detail and resulted in that tunable and white-light emission can be obtained by modulating Eu3+ doping concentration. White emission can be realized with the CIE coordinates of (0.357, 0.345) and quantum efficiency of 57.6% for Ba 9 Y 2 Si 6 O 24 :0.024Bi3+,0.02Eu3+. The above results demonstrate that Ba 9 Y 2 Si 6 O 24 :Bi3+,Eu3+ may be a potential candidate for ultraviolet (UV) driven white light-emitting diodes (w-LEDs). • Luminescence and energy transfer of Ba 9 Y 2 Si 6 O 24 :Bi3+,Eu3+ phosphor were investigated. • The highest QE can reach 64.5% in BYSO:0.024Bi3+ phosphor. • White emission can be obtained in BYSO:0.024Bi3+,0.02Eu3+ sample with QE of 57.6%. [ABSTRACT FROM AUTHOR]

Abstract A batch of Bi3+/Eu3+ single and co-doped BaGd 2 O 4 phosphors were elaborated by traditional high temperature solid-state method. Their structural and photoluminescent properties were methodically studied by X-ray diffraction (XRD), scanning electron microscope (SEM), excitation spectra, emission spectra, decay curves as well as temperature dependent emission spectra. Under ultraviolet (UV) excitation, via a high-efficiency energy transfer process, the prepared Bi3+/Eu3+ co-doped BaGd 2 O 4 phosphors reveal both blue wide emission from Bi3+ ions and characteristic red sharp emission from Eu3+ ions. The energy transfer mechanism, energy transfer efficiency and luminescence chromaticity coordinates were procured. Our results indicate that BaGd 2 O 4 :Bi3+, y Eu3+ phosphors may act as promising candidate to boost the photosynthesis of plant. [ABSTRACT FROM AUTHOR]

• The preparation technology of Y 2 Mg 2 Al 2 Si 2 O 12 :Bi3+,Eu3+ phosphors is simple. • The main emission peak of Eu3+ and emission band of Bi3+ are well separated. • Y 2 Mg 2 Al 2 Si 2 O 12 :Bi3+,Eu3+ phosphors exhibit excellent thermal stability. • Relative sensitivity S r accelerates with rising temperature. An array of Y 2 Mg 2 Al 2 Si 2 O 12 :Bi3+,Eu3+ phosphors were successfully manufactured. The crystal phase, microscopic image and optical properties were systematically surveyed with X-ray diffraction patterns, scanning electron microscopy and fluorescence spectra, respectively. Under 282 nm excitation, for Y 2 Mg 2 Al 2 Si 2 O 12 :Bi3+ phosphors, a broadband emission center located at 319 nm was observed, which is derived from the 3P 1 → 1S 0 transition. For Bi3+/Eu3+ co-doped samples, besides the 319 nm emission of Bi3+, a range of characteristic sharp lines of Eu3+ were observed. Meanwhile, the maximum efficiency of energy transfer (Bi3+ → Eu3+) can arrive to 89.5%. According to the emission spectra at different temperature, the samples present an excellent temperature sensing property based on fluorescence (from Bi3+ and Eu3+) intensity ratio and thermal stability. The maximum relative sensitivity S r reaches to 0.544 %K−1 at 573 K. The emission intensity at 483 K maintains 95.5% of that at 303 K. All above meaningful results indicate that the samples may have certain application value in the field of temperature measurement. [ABSTRACT FROM AUTHOR]

A series of Eu2+/Tb3+/Eu3+ co-doped oxyfluoride aluminosilicate glass samples were synthesized by using the melt-quenching method in air atmosphere. Transmission spectra, excitation and emission spectra, decay curves and temperature-dependent emission spectra were utilized to investigate their luminescent properties systematically. Under near-ultraviolet excitation, adjustable white light emission is generated as a result of efficient energy transfer from Eu2+ to Tb3+ and from Tb3+ to Eu3+. Furthermore, the Eu2+/Tb3+/Eu3+ co-doped glass presents good thermal stability. At 423 K, the emission intensity of the optimal G-5Tb4Eu glass remains about 86% of its initial intensity at 298 K. These excellent properties indicate that Eu2+/Tb3+/Eu3+ co-doped oxyfluoride aluminosilicate glass may provide a new platform for designing and fabricating W-LEDs devices in the future. • Luminescence and energy transfer of Eu2+/Tb3+/Eu3+ co-doped oxyfluoride aluminosilicate glass were investigated. • The highest QE can reach 56.4% in G-5Tb0.2Eu glass excited by 378 nm. • At 423 K, the emission intensity of the optimal G-5Tb4Eu glass remains about 86% of its initial intensity at 298 K. [ABSTRACT FROM AUTHOR]