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Phosphor-converted white light-emitting diodes (pc-wLEDs) are drawing ever-increasing attention towards electronic applications. However, thermal quenching, the intensity decay with increasing temperature, presents a significant challenge for high power operation. We reverse the effect with a negative-thermal-quenching property based on energy transfer from one luminescent center to another center. The LaMgAl 11 O 19 : Er3+, Sm3+ (LMA: LaMgAl 11 O 19 : Er3+, Sm3+) phosphor has been designed, which shows a positive relationship between emission intensity and operating temperature up to 573 K (300 °C). As the temperature rises, energy transfer from Er3+ to Sm3+ occurs with higher efficiency because of stronger ionic vibration. As a result, the phosphor luminescence intensity at elevated temperatures is enhanced. Our design for negative-thermal quenching phosphor laid the foundation for the research of high-power pc-wLEDs or lasers at higher temperatures. It also has potential for wide-temperature-sensing-range radiometric optical thermometry applications. • A negative thermal-quenching phosphor LaMgAl 11 O 19 : Er3+, Sm3+ was achieved by energy transfer. • The emission intensity of the phosphor increased continuously with temperature from 298 K to 573K. • The phosphor was promising for high power wLED operations and high temperature radiometric optical thermometry. [ABSTRACT FROM AUTHOR]

Graphical abstract Na 3 GdP 2 O 8 : Sm3+ and Na 3 GdP 2 O 8 : Dy3+ phosphors were successfully prepared and emitted orange-red and white light under UV/NUV excitation, respectively. The excellent thermal stability further indicated that these phosphors have great potential for applications in UV/NUV excited w-LEDs. Highlights • The novel Sm3+ and Dy3+ ions doped Na 3 GdP 2 O 8 phosphors were prepared. • Both orange-red and white lights could obtain with excellent thermal stability. • These phosphors are potential for application in UV/NUV based w-LEDs. Abstract With the rapid demand of white light emitting diodes (w-LEDs), studies on the ultraviolet/near-ultraviolet (UV/NUV) light excited phosphors are becoming more and more important. Herein the novel Na 3 GdP 2 O 8 : Re3+ (Re = Sm, Dy) phosphors were synthesized through a high-temperature solid-state reaction method. The Sm3+-doped Na 3 GdP 2 O 8 phosphors emitted orange-red light centered at 600 nm, under the NUV excitation at 403 nm. When excited at 350 nm, the Na 3 GdP 2 O 8 : Dy3+ phosphors presented a white light emission, including three peaks at 483, 578, and 670 nm, respectively. In addition, both of the Na 3 GdP 2 O 8 : Sm3+ and Na 3 GdP 2 O 8 : Dy3+ phosphors showed excellent thermal stability at different temperatures, of which the emission intensities at 150 °C could maintain about 75% and 79% of those at room temperature, respectively. These results indicate that the as-prepared phosphors can be considered as potential candidates for applications in UV/NUV excited w-LEDs. [ABSTRACT FROM AUTHOR]

The Eu 3+ ion activated pyrochlore-type La 2 Zr 2 O 7 red emitting phosphor was prepared through solid-state reaction. The electronic structure of La 2 Zr 2 O 7 was investigated with density functional theory (DFT) calculation. The phase purity, crystalline structure, morphology and lattice parameters of the Eu 3+ ion doped La 2 Zr 2 O 7 through powder X-ray diffraction and Rietveld refinement were also elucidated in details. The as-prepared La 2 Zr 2 O 7 : Eu 3+ phosphors presented excellent red light emission with intense absorption bands in the near-ultraviolet and blue light regions. The optimized doping concentration of Eu 3+ ions was found to be 0.05 with an ideal CIE coordinate index of (0.62, 0.38). Finally, the excellent thermal stability of La 2 Zr 2 O 7 : Eu 3+ phosphor was also determined according to the temperature dependent emission spectra, excited at 393 nm. All these results indicated that the La 2 Zr 2 O 7 : Eu 3+ phosphors had high potential for applications in solid-state white light-emitting diodes as suitable red-emitting components for white light emitting diodes (w-LEDs), combined with near-ultraviolet or blue lighting chips. [ABSTRACT FROM AUTHOR]

Emission color tunable single-phased phosphors La 7 O 6 (BO 3 )(PO 4 ) 2 : Ce 3+ , Tb 3+ , Eu 3+ were prepared by a solid state reaction method. The crystal structure, luminescence properties, energy transfer, and co-excitation behavior were investigated in detail. The La 7 O 6 (BO 3 )(PO 4 ) 2 : x Ce 3+ phosphors emit blue light under the excitation at 228 nm, corresponding to the broad 4f-5d transition of Ce 3+ . Concentration quenching phenomenon was observed when the Ce 3+ ion was x = 0.01. By co-doping the Eu 3+ and Tb 3+ ions into La 7 O 6 (BO 3 )(PO 4 ) 2 : Ce 3+ phosphors, the emission color can be tunable from blue to reddish, and then to white. The energy transfer from Ce 3+ to Eu 3+ and the co-excitation of Ce 3+ and Tb 3+ have been investigated and discussed. The color coordinate for the La 7 O 6 (BO 3 )(PO 4 ) 2 : 0.01Ce 3+ , 0.05Tb 3+ , 0.05Eu 3+ phosphor is calculated to be (0.3008, 0.3381). [ABSTRACT FROM AUTHOR]

Novel LaMgAl 11 O 19 :Pr 3+ phosphors for blue light pumped white light emitting diodes (w-LEDs) were prepared via a solid state reaction. The structure and luminescence properties were investigated. The LaMgAl 11 O 19 :Pr 3+ phosphors emitted a yellow light under excitation at 446 nm, which contains a green emission band, a red emission band, and a weak near infrared emission band. Concentration quenching, due to non-radiative energy transfer between Pr 3+ ions via the exchange interaction was observed when the Pr 3+ ion concentration was 0.1 mol. The colour coordinate for the yellow LaMgAl 11 O 19 :0.1Pr 3+ phosphor was calculated to be (0.4497, 0.5306). These results indicate that the LaMgAl 11 O 19 :0.1Pr 3+ phosphor can be combined with blue LED chips and can be widely used in w-LEDs application. [ABSTRACT FROM AUTHOR]

An orange reddish emitting phosphor, LaMgAl 11 O 19 :Sm 3+ , was synthesized by a high temperature solid-state reaction, and the phase formation, crystal structure and luminescence properties were investigated respectively. The LaMgAl 11 O 19 :Sm 3+ phosphor presents a highly intense orange reddish emission peak under the near ultraviolet excitation at 403 nm, which is corresponds to the 4 G 5/2 → 6 H J ( J = 5/2, 7/2, 9/2 and 11/2) transitions of Sm 3+ ions. It was found that the dipole–dipole interactions mainly results in the concentration quenching in the LaMgAl 11 O 19 :Sm 3+ phosphor with a critical quenching concentration at about 5 mol%. The temperature dependence of luminescence properties was studied from 25 to 200 °C and indicated that LaMgAl 11 O 19 :0.05Sm 3+ phosphors had a relatively higher quenching temperature. The chromatic properties of LaMgAl 11 O 19 :0.05Sm 3+ phosphor have been found to have chromaticity coordinate of (0.578, 0.420). All these properties indicate that the orange reddish emitting LaMgAl 11 O 19 :Sm 3+ phosphor has a potential application in w-LEDs. [ABSTRACT FROM AUTHOR]

Nitrided LaMgAl11O19 phosphors were prepared by a two-step method involving synthesis at 1550°C for 4h, trituration, and firing at 1650°C for 5h under a nitrogen atmosphere. Nitrogen was doped into LaMgAl11O19 and bonded with aluminium atoms. The nitrided LaMgAl11O19 phosphors showed plate-like morphology with a rough surface and exhibited strong blue emission at 442nm and 450nm, which may be attributed to the energy transition between defect levels. A weak emission band at 590nm was ascribed to the transition between the VAl acceptor and the valence band, which was excited at 254nm. [ABSTRACT FROM AUTHOR]

Abstract: The LaMgAl11O19:Dy3+ phosphors were prepared by the high-temperature solid-state reaction method. The phase structure, luminescence properties, and the thermal stability of the phosphors were investigated. Under the excitation of 349nm, the LaMgAl11O19:Dy3+ phosphors exhibited three emission peaks at 475nm, 570nm, and 664nm, which respectively corresponded to the 4F9/2→6H15/2, 4F9/2→6H15/2, and 4F9/2→6H11/2 transitions. It was proved that dipole–dipole interaction resulted in the concentration quenching with a quenching concentration of 0.1mol. The emission intensity at 150°C was stronger than that at 25°C, indicating the good thermal stability of LaMgAl11O19:Dy3+ phosphors. The CIE coordinates of LaMgAl11O19:Dy3+ phosphors are very close to the white light coordinates (x=0.3333 and y=0.3333). Therefore, LaMgAl11O19:Dy3+ phosphor is a promising single-phase phosphor for white light emitting diodes. [Copyright &y& Elsevier]

A range of Eu3+-doped AMoO 4 (A = Ca and Ba) phosphors were successfully synthetized, and their crystal structures, optical performance, and temperature measurement sensitivities were investigated in detail. Peak doping concentration of CaMoO 4 :Eu3+ phosphor was 0.18, while peak doping concentration of BaMoO 4 :Eu3+ phosphor may be greater than 0.18. Then, temperature-dependent photoluminescence emission spectra of representative CaMoO 4 :0.09Eu3+ and BaMoO 4 :0.03Eu3+ phosphors were recorded. CaMoO 4 :0.09Eu3+ phosphor exhibited abnormal thermal quenching, which was attributed to defects caused by heterovalent substitution of ions and increase in the temperature, and good thermal stability. Finally, the possibility of using both phosphors as optical thermometers was discussed, which exhibited good temperature sensitivity. However, CaMoO 4 :0.09Eu3+ phosphor exhibited two peak absolute (Sa, 1.28 %K−1 and 1.39 %K−1) and relative sensitivities (Sr, 1.21 %K−1 and 1.20 %K−1). In addition, variation trend of Sr value with temperature was considerably peculiar. Two optimum Sa and Sr values were attributed to abnormal thermal quenching of CaMoO 4 :0.09Eu3+ phosphor. Peak Sa and Sr values of BaMoO 4 :0.03Eu3+ phosphor was 12.39 %K−1 and 0.89 %K−1, respectively. In addition, Sa of AMoO 4 :Eu3+ phosphor was negatively related to Eu3+ central asymmetry, while peak Sr value was more inclined to appropriate ionic central asymmetry. [ABSTRACT FROM AUTHOR]

The single-component BiOCl:Dy3+ white-light-emitting phosphor was successfully prepared. The luminescence performance with excellent thermal stability indicated that this as-prepared product could act as a high-performance phosphor candidate for n-UV w-LED application. • The single-component BiOCl:Dy3+ phosphor was prepared successfully. • The phosphor emitted white light under the excitation in n-UV light region. • The PL properties obtained excellent thermal stability at higher temperatures. • The phosphor could have great potential for n-UV w-LED application. The advantages of single-component white-light-emitting phosphor make it more important for n-UV-light emitting diodes with excellent properties and efficiency. Herein, the BiOCl:Dy3+ white-light-emitting phosphor was firstly prepared by high temperature solid-state reaction. And the crystal structure, luminescence properties, lifetime, and thermal quenching behavior were carried out in detail. The results revealed that the BiOCl:Dy3+ phosphor could be excited efficiently in a broad near ultraviolet (n-UV) light region, which matched well with the n-UV chips for w-LEDs. Under the excitation at 390 nm, the BiOCl:Dy3+ phosphor exhibited white light with three emission peaks centered at 481, 575, and 664 nm, respectively. The optimal doping concentration of Dy3+ ions was found to be x = 0.03, and exchange interaction was confirmed to result in the concentration quenching. Furthermore, when the test temperature turned up to 150 °C, the intensity of emission peaks at 481 and 575 nm could still remain 77.96% and 77.93% of the initial intensity at room temperature. With the their activation energy of 0.33 eV and 0.27 eV, the excellent thermal stability of the BiOCl:Dy3+ phosphor were confirmed. All these results indicated that this as-prepared product could act as a high-performance phosphor candidate for n-UV w-LED application. [ABSTRACT FROM AUTHOR]

In this study, La 2 (MoO 4) 3 doped with Eu3+ was synthesized by the high-temperature solid-state method. The phase composition of the Eu3+-doped La 2 (MoO 4) 3 sample was confirmed by X-ray powder diffraction (XRD) analysis, and the microstructure was observed via the scanning electron microscopy (SEM). Under the excitation at 211 nm, the room temperature emission spectra of Eu3+ in the samples with different doping levels were recorded. In addition, the prepared La 2 (MoO 4) 3 : x Eu3+ (x = 0–0.25) phosphors were color tunable. A non-contact optical thermometer with high sensitivity and high-temperature resolution was fabricated based on the different thermal quenching behaviors of the Mo–O group and Eu3+ center. The fluorescence intensity ratio (FIR), temperature resolution (ΔT), maximum absolute and relative sensor sensitivity (Sa and Sr) of La 2 (MoO 4) 3 :Eu3+ were calculated according to different thermal quenching effects between room temperature (298K) and 573K of Eu3+ and Mo–O group. These results show that La 2 (MoO 4) 3 :Eu3+ has excellent sensitivity and temperature resolution, good reversibility and reliability, as Sa = 0.0525 K-1, Sr = 0.3724. % K−1, ΔT = 0.0806 K and the FIR error was only 0.62%. Therefore, the Eu3+-doped La 2 (MoO 4) 3 is a promising candidate material for high performance non-contact optical thermometers. [ABSTRACT FROM AUTHOR]

Recently, blue-emitting phosphors have attracted great interest due to their application in full-spectrum white light illumination. In this paper, a novel blue-emitting MgAl2Si4O6N4:Eu2+ phosphor was successfully synthesized through the solid-state reaction method in a reducing atmosphere. Under the excitation of near-ultraviolet (n-UV) light, the MgAl2Si4O6N4:0.02Eu2+ phosphor effectively emits a broad blue emission band centered at 456 nm with the FWHM as large as 81 nm. With the increasing Eu2+ concentration, the emission bands of MgAl2Si4O6N4:Eu2+ shift to a shorter wavelength and the FWHMs broaden gradually. Moreover, the MgAl2Si4O6N4:0.02Eu2+ phosphor exhibits a slight thermal quenching at a higher temperature. After fabricating the as-prepared MgAl2Si4O6N4:0.02Eu2+ phosphor into a white LED device, the intense neutral white light emission is obtained with excellent CRI (87.4) and CCT (5645 K). These results suggest that the blue MgAl2Si4O6N4:Eu2+ phosphor is a promising candidate in n-UV excited white LEDs. [ABSTRACT FROM AUTHOR]

A high temperature solid state method was used to prepare Na3Gd(PO4)2:Eu2+,Mn2+ phosphors with good thermal stability. The phosphor shows a broadband excitation region of 250–430 nm, which can be matched with the emissions of ultraviolet (UV)/near-ultraviolet (NUV) LED chips for white light emitting diodes (w-LEDs). The energy transfer efficiency is 74.46% from the sensitizer Eu2+ ions to the activator Mn2+ ions, which enhances the intensities of the Na3Gd(PO4)2-based phosphor. In addition, by increasing the Mn2+ doping level in the phosphor, the Na3Gd(PO4)2:Eu2+,Mn2+ phosphor first shows blue light, then turns to white light, and finally emits red light under 365 nm excitation. Besides, the temperature-dependent photoluminescence measurements indicate that the prepared phosphors exhibit good thermal stability. W-LEDs fabricated by combining a 365 nm chip with the Na3Gd(PO4)2:Eu2+,Mn2+ phosphor exhibit bright white light, which has a high color rendering index (CRI) = 91.5, and a relatively low correlated color temperature (CCT) = 5198 K. Moreover, the CIE point is calculated to be at (0.3337, 0.3465), which is located in the white light region. These results indicate that the as-prepared phosphors can be considered as potential candidates for UV/NUV light-excited w-LED applications. [ABSTRACT FROM AUTHOR]

Red phosphors with a high quantum yield and a lower thermal quenching are needed to improve the luminescence efficiency and the stability of phosphor-converted white light-emitting diodes (pc-WLEDs). We have designed a high quantum yield NaGdSiO 4 (NGSO) based phosphor with enhanced Eu3+ emissions of the 5D 0 →7F 1 and 5D 0 →7F 2 transitions. This design is based on the Eu3+ at both the inversion and non-inversion symmetry sites. In detail, we have studied the structure, morphology, and luminescence properties of NGSO: Eu3+ phosphors. Using a 394 nm UV excitation, a series of Eu3+ emissions of 5D 0 →7F J (0–4) transitions has been observed. The internal quantum efficiency (IQE) is 83.42% and the red color purity is 91.4%. These values are much higher than some reported results. The higher IQE and double intense 5D 0 →7F 1 and 5D 0 →7F 2 emissions might originate from an unusual structure disorder around Eu3+ ions in the NGSO lattice. The lifetime of the optimal phosphor NGSO: 0.5Eu3+ is about 2 ms, suitable for solid-state lighting. The intensities of the strong emissions at 595 and 624 nm of NGSO: 0.5Eu3+ at 150 °C is about 85% of that at 30 °C, demonstrating its excellent thermal stability. Furthermore, this red NGSO: 0.5Eu3+ phosphor was packaged into a warm pc-WLED, exhibiting a lower correlated color temperature (CCT) of 4222 K and a comparable color rendering index (CRI) of 86.7. These results show that this red phosphor could act as a red component of pc-WLEDs excited by the n-UV LED chip. [ABSTRACT FROM AUTHOR]

Using the solid-state method, a novel optical thermometer, RbCaLa 1-x (VO 4) 2 : x Eu3+ phosphor, was synthesized. Using X-ray diffraction, the phase of the RbCaLa 1-x (VO 4) 2 : x Eu3+ was confirmed. The microstructure was then observed in the SEM pattern. To estimate the temperature, the fluorescence intensity ratio (FIR) method was used. To explain the temperature-sensing properties, the absolute (Sa) and relative (Sr) sensitivities were calculated. The maximum Sa and Sr values were then determined as 2.215% and 1.125% at 473 and 423 K, respectively. After multiple heating and cooling processes, the FIR value corresponding to each temperature stabilized. This indicated the reliability of the FIR fitting formula. Subsequently, to examine the formula's accuracy, multiple temperature points ranging from 298 to 473 K were selected. The results demonstrated that the measurement error could be controlled in ±1.1 K. The difference was considerably lesser in the high-temperature region (400–430 K), and the error was in ±0.21 K. Under UV light, the colors of the RbCaLa 0.82 (VO 4) 2 :0.18Eu3+ phosphor and RbCaLa(VO 4) 2 matrix were somewhat different, and both considerably changed with temperature. All results showed that the Eu3+-doped RbCaLa(VO 4) 2 phosphor is a good candidate material as an optical temperature sensor and anti-counterfeiting coating. [ABSTRACT FROM AUTHOR]

Two cyan-emitting phosphors with different bandwidths were successfully synthesized through the high-temperature solid-state method in a reducing atmosphere. The crystal structures, morphologies, and luminescence properties of the as-prepared phosphors were investigated. The Rietveld refinements of the powder X-ray diffraction (XRD) data demonstrated the single phase of the samples, and two crystallographic sites of La3+ were observed in the crystal structure. Under the excitation of UV light, both Ba 0.45 Ca 2.5 La 6 (SiO 4) 6 : 0.05 Eu2+ and Ba 1.45 Ca 1.5 La 6 (SiO 4) 6 : 0.05 Eu2+ phosphors emitted cyan light due to the 4f65 d1→4f7 transitions of the Eu2+ ion. The emission spectra could be well fitted by two component Gaussian peaks corresponding to two different coordination environments of the Eu2+ ions. The temperature-dependent photoluminescence spectra show a large difference on the thermal stability between the two phosphors. The two phosphors exhibit effective absorption of near-UV light and their internal quantum efficiencies (IQEs) were calculated as 31.5% and 42.4% under 295 nm UV-light excitation. The experimental results indicate that the novel cyan phosphors might have potential applications in white light-emitting diodes (LEDs) based on the near-UV LED chip. [ABSTRACT FROM AUTHOR]

Na 3 Gd(PO 4) 2 phosphors doped with rare-earth metal ions Ce3+ and Tb3+ were fabricated by the solid-state reaction method. Under the excitation of 340 nm light, the Ce3+-doped Na 3 Gd(PO 4) 2 phosphors exhibit a broad emission band ranging from 370 nm to 480 nm, which emitted blue light centered at 405 nm. When excited at 373 nm, the Tb3+-doped Na 3 Gd(PO 4) 2 phosphors presented a green light emission, including a strong peak located at 547 nm. In addition, both of the Na 3 Gd(PO 4) 2 : Ce3+ and Na 3 Gd(PO 4) 2 : Tb3+ phosphors showed excellent thermal stability at different temperatures, be specific in the Na 3 Gd(PO 4) 2 : Ce3+ emission intensities at 150 °C could maintain about 84 % and the Na 3 Gd(PO 4) 2 : Tb3+ could maintain about 92.9 % of those at room temperature. A prototype of the white light-emitting diodes lamp exhibiting bright white light was fabricated by using a 365 nm near-ultraviolet-emitting LED chip, combined with Na 3 Gd(PO 4) 2 : Ce3+ blue phosphors, Na 3 Gd(PO 4) 2 : Tb3+ green phosphors, and Na 3 Gd(PO 4) 2 : Eu3+ red phosphors, which produced a high color rendering index of 89.4, and a relatively low correlated color temperature of 5496 K. Moreover, the CIE point was calculated to be at (0.3332, 0.3438), locating in the white light region. These results indicate that the as-prepared phosphors can be considered as potential candidates for ultraviolet/near-ultraviolet light-excited white light-emitting diodes applications. • The Na 3 Gd(PO 4) 2 : Ce3+, Tb3+ phosphors were prepared with excellent thermal stability. • Both blue and green light phosphors have high internal quantum efficiency. • The CRI, CCT and CIE coordinate of the self-made w-LED has good performance. • The phosphors are potential for application in UV/NUV based w-LEDs. [ABSTRACT FROM AUTHOR]

Advances in solid-state white-light-emitting diodes (WLEDs) necessitate the urgent development of highly efficient single-phase phosphors with tunable photoluminescence properties. Herein, the Tm3+, Dy3+, and Sm3+ ions are incorporated into the orthorhombic NaGdTiO4 (NGT) phosphors, resulting in phosphors that fulfill the aforementioned requirement. The emission spectrum of Tm3+ ions overlaps well with the adsorption spectra of both Dy3+ and Sm3+ ions. Under the excitation at 358 nm, the single-phase NaGdTiO4: Tm3+, Dy3+, Sm3+ phosphor exhibits tunable emission peaks in the blue, yellow, and red regions simultaneously, resulting in an intense white-light emission. The coexisting energy transfer behaviors from Tm3+ to Dy3+ and Sm3+ ions and the energy transfer from Dy3+ to Sm3+ ions are demonstrated to be responsible for this phenomenon. The phosphors with multiple energy transfers enable the development of single-phase white-light-emitting phosphors for phosphor-converted WLEDs. [ABSTRACT FROM AUTHOR]

The constructed high-efficient cyan-emitting phosphors establish a bifunctional platform involving high-color-quality lighting and anti-counterfeiting application. [Display omitted] • Ca 8 ZnY(PO 4) 7 :Eu2+ phosphors exhibited a broad cyan-emitting spectra (FWHM = 78 nm). • The quantum yield of Ca 8 ZnY(PO 4) 7 :Eu2+ phosphor is as high as 72.11 %. • The CRI value of warm w -LED devices was greatly enhanced from 83.9 to 90.5. • The transparent anticounterfeiting film held great potentials in packaging field. Constructing the broad-band emitting luminescent materials with high quantum yield is of great significance towards their widespread applications. Herein, series of Eu2+ activated, whitlockite-type Ca 8 ZnY(PO 4) 7 phosphors are developed towards bifunctional platform involving the white LED and anti-counterfeiting field. Benefiting from the typical 5d-4f transitions among Eu2+ ions, the broad asymmetric cyan-emission spectra (FWHM = 78 nm) is generated under 365 nm excitation with a highest quantum yield of ∼72.11 %. The optimal doping concentration of Eu2+ ions in the Ca 8 ZnY(PO 4) 7 host is determined as 4 % and the concentration quenching mechanism is mainly attributed to a dipole–dipole interaction. Impressively, after exploiting the newly discovered cyan-emitting phosphors Ca 8 ZnY(PO 4) 7 :Eu2+, the CRI value of as-prepared warm w -LED devices is remarkably enhanced from 83.9 to 90.5. Moreover, the w -LED exhibits an applicable correlated color temperature (CCT = 4176 K) and good color stability. Additionally, the transparent anticounterfeiting film is fabricated based on the highly efficient phosphors and soluble PVA, which presents anticounterfeiting performances due to their bright cyan emission upon UV light. Notably, their sustainability, excellent flexibility and foldability provide more possibilities applied for anticounterfeiting field. These results suggest the highly efficient phosphors Ca 8 ZnY(PO 4) 7 :Eu2+ are promising bifunctional luminescent platforms, for both high-color-quality lighting and anticounterfeiting applications. [ABSTRACT FROM AUTHOR]

Eu 3+ doped BaMg 2 V 2 O 8 (BMVO) phosphor was synthesized via a high temperature solid-state reaction method. When λ ex = 318 nm and Eu 3+ was doped, the VO 4 3− peak at 545 nm decreased, and a characteristic Eu 3+ peak occurred together with a maximum at 620 nm. In conjunction with the decay curve, this indicates that the energy transfer from VO 4 3− to Eu 3+ . Upon doping with Eu 3+ , the phosphor becomes color-tunable. In addition, changing the temperature between 25 and 200 °C, BMVO:0.05Eu 3+ phosphor also becomes color-tunable. All results indicate that Eu 3+ doped BaMg 2 V 2 O 8 phosphor has many promising commercial applications. [ABSTRACT FROM AUTHOR]

A series of apatite-type phosphors Ba 4.97− x Sr x (PO 4 ) 3 Cl:Eu 2+ ( x = 0, 0.5, 1.0, 1.5, 2.0) were synthesized by the high temperature solid-state reaction method, and its luminescence properties were investigated in detail. It can be found that a red shift of the emission peak wavelength emerged from 439 to 462 nm with the continuous introduction of Sr 2+ into the crystal lattice which has been simulated by a crystal-field model. The red shift is explained by the distortion in the crystal structure through X-ray diffraction and the Rietveld refinement analysis. According to a recently raised structural model, Eu 2+ ions are surrounded by O atoms, PO 4 tetrahedrons and Ba/Sr ions. After introducing Sr 2+ into the lattice, the interatomic distance between Ba/Sr atoms and Eu 2+ was expected to become shorter, resulting in a distortion of the inner EuO n polyhedrons. Then the crystal field strength surrounding Eu 2+ was increased, finally resulting in the red shift. [ABSTRACT FROM AUTHOR]

Na 3 Gd(PO 4) 2 : Dy3+, Eu3+ phosphors were obtained by the co-doping of Dy3+ and Eu3+, and the red light emitted by Eu3+ solved the issue of high CCT due to the lack of a red-light band in the emission spectra of Dy3+. The CIE coordinate of the Dy3+and Eu3+co-doped Na 3 Gd(PO 4) 2 phosphors is calculated as (0.3442, 0.3320), which is located in the white region. The excellent thermal stability further indicated that the phosphors have great potential for applications in UV/NUV excited w-LEDs. [Display omitted] In this study, novel Na 3 Gd(PO 4) 2 :Dy3+, Eu3+ phosphors were synthesized by a high-temperature solid-state method. Single-phase white lighting-emitting Na 3 Gd(PO 4) 2 :Dy3+ phosphors exhibited blue and yellow emissions under 350 nm excitation, respectively. Eu3+-doped phosphors exhibited strong red emission at 621 nm under 394 nm excitation. Compared with that of Na 3 Gd(PO 4) 2 :Dy3+, the color rendering index of Na 3 Gd(PO 4) 2 :Dy3+, Eu3+ phosphor is improved from 74.7 to 78.9. Moreover, the correlated color temperature of Na 3 Gd(PO 4) 2 :Dy3+, Eu3+ reduced significantly from 9872 K to 5460 K. The maximum energy transfer from Dy3+ to Eu3+ in Na 3 Gd(PO 4) 2 :Dy3+, Eu3+ phosphor was ∼ 76.2% at Eu3+ concentration of 0.1. The chromaticity coordinate of the Dy3+ and Eu3+co-doped Na 3 Gd(PO 4) 2 phosphor was calculated as (0.3442, 0.3320), which is located in the white region. Furthermore, temperature-dependent photoluminescence emission properties indicate that the prepared phosphors exhibit good thermal stability. The study results indicate that the Na 3 Gd(PO 4) 2 :Dy3+, Eu3+ phosphors exhibit immense potential for ultraviolet/near-ultraviolet light-excited white light emitting diodes applications. [ABSTRACT FROM AUTHOR]

A series of novel Eu 3+ doped tungstate Li 2 Mg 2 (WO 4 ) 3 red phosphors were successfully synthesized by a solid-state reaction method. The phase structure, photoluminescence properties and thermal stability of the phosphor were investigated in detail. The Li 2 Mg 2 (WO 4 ) 3 :Eu 3+ phosphors show dominant emission peak at 620 nm ( 5 D 0 → 7 F 2 transition) upon the strongest excitation at 398 nm ( 7 F 0 → 5 L 6 transition). The optimal doping concentration of Eu 3+ is determined to be 0.06 mol in order to obtain the maximum emission intensity. The dependence of the emission intensity on temperature denominates that Li 2 Mg 2 (WO 4 ) 3 :Eu 3+ phosphor has a relatively good thermal quenching effect. The Commission Internationale del’Eclairage coordinates was measured as (0.678, 0.322) with high color purity, being close to the National Television Standard Committee system standard for red chromaticity (0.670, 0.330). The above studies indicate that Li 2 Mg 2 (WO 4 ) 3 :Eu 3+ is a promising candidate as the red phosphor for near ultraviolet-based white LEDs application. [ABSTRACT FROM AUTHOR]

The fabrication and luminescent performance of novel phosphors Na2YMg2V3O12:Dy3+ were investigated by a conventional solid-state reaction method. Under near-UV light, the Na2YMg2V3O12 host self-activated and released a broad emission band (400–700 nm, with a peak at 524 nm) ascribable to charge transfer in the (VO4)3− groups. Meanwhile, the Na2YMg2V3O12:Dy3+ phosphors emitted bright yellow light within both the broad emission band of the (VO4)3- groups and the sharp peaks of the Dy3+ ions at 490, 582, and 663 nm at a quenching concentration of 0.03 mol. The emission of the as-prepared Na2YMg2V3O12:Dy3+ phosphors remained stable at high temperatures. The obtained phosphors, commercial Y2O3:Eu3+ red phosphors, and BaMgAl10O17:Eu2+ blue phosphors were packed into a white light-emitting diode (WLED) device with a near-UV chip. The designed WLED emitted bright white light with good chromaticity coordinates (0.331, 0.361), satisfactory color rendering index (80.2), and proper correlation to a color temperature (7364 K). These results indicate the potential utility of Na2YMg2V3O12:Dy3+ phosphor as a yellow-emitting phosphor in solid-state illumination. [ABSTRACT FROM AUTHOR]

Rare earth aluminate phosphors are well-known for being nontoxic and environmentally friendly. In this work, Tb3+-doped SrLaAlO 4 phosphors were synthesized via a facile high temperature solid-state reaction method. The Optimum reaction temperature is determined to be 1300 °C based on the results of powder X-ray diffraction (XRD). The SEM patterns and TEM images correspond with the results of Rietveld refinement and show that the SrLa 1-x AlO 4 :xTb3+ samples present a flaky structure. The results of photoluminescence spectrums (PL) show that SrLa 1-x AlO 4 :xTb3+ phosphors can absorb in the UV–vis spectral region of 228 nm–263 nm and exhibit several emission peaks between 450 and 650 nm, and the highest peak was at 508 nm. The luminescence properties of SrLa 1-x AlO 4 :xTb3+ have a strict dependence on the cation substitution levels. When the doping concentration of Tb3+ was 0.05, the emission intensity of the sample is strongest. The thermal quenching result of the SrLa 0.95 AlO 4 :0.05 Tb3+ phosphors shows that these phosphors are relatively sensitive to temperature changes under an excitation of 228 nm, as the temperature increases from 25 °C to 125 °C, the emission intensity (peak at 548 nm) decayed to 55.11% of that at room temperature. However, when the temperature increases to 125 °C, the emission intensity (peak at 548 nm) decayed to 61.16% of the initial value under an excitation of 263 nm, which showed a relatively good thermal stability. The internal quantum efficiency (QE) values of the SrLa 0.95 AlO 4 :0.05 Tb3+ phosphors was measured and determined to be 48%. Under excitations of 228 nm and 263 nm, the lifetimes of the optimized sample SrLa 0.95 AlO 4 :0.05 Tb3+ were 1.3986 ms and 1.2095 ms, respectively, and the CIE coordinates of the sample were calculated as (0.2971, 0.4981), (0.3056, 0.5329), respectively. Under both excitations SrLa 0.95 AlO 4 :0.05 Tb3+ exhibited high-color-purity green emission. • The5D 4.→7F J (J = 6, 5, 4, 3) transitions and 5D 3 →7F J (J = 6, 5, 4) transitions of Tb3+ under UV excitation. • Dexter's theory to explain concentration quenching effect. • The fluorescence decay behavior of the SrLaAlO 4 : Tb3+ phosphor. • The research of the thermal quenching of the SrLaAlO 4 : Tb3+ phosphor. • Distribution of element in SrLaAlO 4 : Tb3+ phosphor investigated by TEM mapping. [ABSTRACT FROM AUTHOR]