Search

Achieving the desired color temperature and color rendering index in light sources is challenging because of the deficiency of certain color components, notably cyan in the illumination spectra. In this investigation, we successfully synthesized orthogonal Ca5Ga6O14: Bi3+ (CGO: Bi3+) phosphors with space group Cmc21, featuring two distinct Ca(1) and Ca(2) sites. Under the excitation of 335 nm, a broad cyan emission with a 495 nm peak was observed. Gaussian peak fitting revealed two sub-peaks at 445 and 500 nm, originating from the emission of Bi3+ occupying Ca(1) and Ca(2) sites, respectively. As Bi3+ doping concentration increased, the luminescence experienced a red shift, attributed to the cooperative impact of crystal field splitting and electron cloud rearrangement. Through the substitution of Sr2+ ions, we achieved a 2.15 times enhancement in emission intensity and an increase in lifetime from 0.451 to 0.551 μs. This substitution also led to a consistent increase in the relative emission percentage of Bi(1) from 46.5% to 73.1%, while that of Bi(2) decreased from 70.5% to 44.9%. It is likely a result of some Bi3+ ions originally situated in the Ca(2) site migrating to the Ca(1) site. Finally, the introduction of Na+ ions for charge compensation resulted in a 20.18% increase in the luminescence intensity and an enhanced quantum efficiency of 84.21%. This CGO: Bi3+ phosphor holds promise as a potential cyan phosphor for white light sources. [ABSTRACT FROM AUTHOR]

Lithium‐containing silicates have been considered as a considerable alternative for luminescent materials. In this study, a novel cyan‐emitting phosphor, Na3LiHf2Si3O12: Eu2+, was successfully synthesized via cationic substitution with Na4Hf2Si3O12: Eu2+ as the initial model. The crystal structure, morphology, and luminescence performance of Na4‐xLixHf2Si3O12: Eu2+ were investigated in detail. The substitution of Li+ for Na+ site causes a significant blue‐shift of the emission band in the range of 550–500 nm and a smaller full width at half maximum. As a result, a cyan phosphor Na3LiHf2Si3O12: Eu2+ that can be effectively excited by near‐ultraviolet and high‐energy beams is obtained. The mechanism of emission regulation was proposed based on the transformation of crystal structure and luminescence performance. In addition, the thermal quenching and cathodoluminescence behaviors were also studied. The results show that cation substitution is an effective method to design new lithium‐containing silicate phosphors. [ABSTRACT FROM AUTHOR]

Cyan phosphors have attracted considerable attention in recent years as an indispensable component for realizing full-spectrum lighting. In this study, a novel nitride-based cyan-emitting phosphor Ca2BN2Cl:Eu2+ was successfully prepared. Its crystal structure refined by the Rietveld refinement reveals that Ca2BN2Cl is formed by a tight host lattice and the edge-sharing Ca(N,Cl)4 tetrahedrons along with multiple crystallographic Ca sites for Eu2+ ions to occupy, which corresponds to its broad emission band. Under the near ultraviolet (NUV) light excitation, Ca2BN2Cl:Eu2+ emits a broad-band cyan light and its full width at half-maximum (FWHM) can reach 121 nm, which effectively compensates the "cyan cavity". The time-resolved photoluminescence (TRPL) spectra of Ca2BN2Cl:Eu2+ were investigated to expose the energy transfer between the multiple luminescent centers. Furthermore, the temperature-dependent spectra of Ca2BN2Cl:Eu2+ were measured to evaluate its thermal stability. All of the discussion and results reveal that Ca2BN2Cl:Eu2+ is a promising cyan phosphor for use in white light-emitting diodes to realize full-spectrum lighting. [ABSTRACT FROM AUTHOR]

Whitlockite β-Ca3(PO4)2-type materials have multiple crystallographic sites for occupying by rare earth ions to achieve a strong and broadband emitting covering the spectra from cyan to deep red and various abundant heterogeneous substitution ability to develop new luminescent materials. In this work, a broadband emitting Sr8MgGa(PO4)7:Eu2+ (SMGP) phosphor, deriving from β-Ca3(PO4)2 host by cations substitution, was prepared by solid state reaction at high temperature. Based on the Rietveld refinement results, SMGP host possesses a monoclinic system with a space group C2/m. The optimized doping concentration was determined to be 0.04. The SMGP: 0.04Eu2+ sample exhibit strong absorption at the wavelength of 250–500 nm, and a broadband emission from 450 to 800 nm covering the spectra from cyan to deep red. However, the SMGP: 0.04Eu2+ phosphors exhibit poor thermal stability with activation energy as 0.156 eV. By adjusting the composition of the trivalent ions Ga3+/Lu3+, controllable emission color from green to yellow can be achieved in the Sr8MgGa1-xLux(PO4)7:Eu2+ solid solution phosphors. Finally, a white light-emitting diodes (LED) lamp was prepared by coating the mixtures of SMGP: 0.04Eu2+ phosphors and BaMgAl10O17:Eu2+ phosphors on the surface of 400 nm near-ultraviolet chip. The optimized white LED lamp exhibits a correlated color temperature of 2991 K and a good color rendering index of 90.2. These results demonstrate the commercialized prospect of SMGP: Eu2+ materials as a broadband emitting phosphor for application in solid state lighting. [ABSTRACT FROM AUTHOR]

[Display omitted] • The large-scale redshift of emission spectrum was realized in R 2- y K y CPOF: Eu2+. • The color-adjustable-emission mechanism in the R 2- y K y CPOF: Eu2+ was illustrated. • Full visible spectrum lighting was realized by R 2- y K y CPOF: Eu2+. Tuning the luminescent properties of phosphors by crystal-site engineering is a good and efficient strategy for developing high-quality white light-emitting diodes (WLEDs). However, it is still challenging to modulate the cyan to red spectral emission in a single matrix and activator phosphor to obtain multicolor output and achieve full-visible-spectrum lighting. Herein, the strategy to manipulate site-selective occupation of Eu2+ activators by substituting the cation Rb+ with K+ is reported to obtain a versatile color output. The large-scale redshift regulation of emission spectrum from cyan to red was achieved in fluor-phosphate Rb 2- y K y CaPO 4 F: 0.0085Eu2+ (R 2- y K y CPOF: 0.0085Eu2+) (0 ≤ y ≤ 1.8) phosphors, which is designed by using Rb 2 CaPO 4 F: 0.0085Eu2+ (RCPOF: 0.0085Eu2+) cyan-emitting phosphor. The redistribution of Eu2+ ions in Rb1, Rb2, and Ca sites is achieved by introducing the cation K+ to substitute Rb+, and R 2- y K y CPOF: 0.0085Eu2+ (0 ≤ y ≤ 1.8) is kept in the pure phase. Furthermore, the mixed phosphors of RCPOF: 0.0085Eu2+, RKCPOF: 0.0085Eu2+, and R 0.2 K 1.8 CPOF: 0.0085Eu2+ show excellent optical performance and good thermal stability. Full-visible spectrum lighting is successfully achieved with the combination of a 395 nm NUV chip and the blend of phosphor-converted WLEDs. The K+ substitution reported in this paper can support a project for warm WLEDs by manipulating the distribution of Eu2+ activator among different cation sites. [ABSTRACT FROM AUTHOR]

Bismuth ions, as excellent non-rare-earth activators for luminescent materials, possess characteristic excitation in the near ultraviolet (n-UV) region rather than in the visible region and could avoid reabsorption as compared to traditional rare-earth (e.g., Eu2+, Ce3+) phosphors. In this work, a series of apatite-type NaGd 9 (SiO 4) 6 O 2 : xBi3+ (NGSO) phosphors with a hexagonal crystal system were synthesized through high-temperature solid-solid reactions. They showed intense n-UV absorption and cyan emission of Bi3+ ions. The optimal Bi3+ doping concentration was 0.02. Further, there were two types of Bi3+ ions that provided seven- and nine-coordination in NGSO: xBi3+ phosphors, resulting in two luminescence centers at 462 and 558 nm, respectively. Bi3+ (Ⅰ) ions were dominant for the emission at 558 nm excited at a wavelength of 340 nm, and Bi3+ (Ⅱ) ions governed the luminescence at 462 nm excitation at 370 nm; energy transfer occurred from Bi3+ (Ⅰ) to Bi3+ (Ⅱ) ions. Finally, good thermal stability with activation energy (E a) of 0.296 eV was demonstrated. These findings exhibit the potential application of NGSO: 0.02Bi3+ phosphors as cyan phosphors in n-UV white light-emitting diodes. [ABSTRACT FROM AUTHOR]

The site occupation engineering of activators in the phosphor directly affects its luminescence properties; thus, revealing the relationship between the site occupation and the activator luminescence is of great significance. In this work, a high efficiency green phosphor Sr 8 CaLu(PO 4) 7 : Eu2+ (SCLP: Eu2+) was successfully constructed based on the model of whitlockite β -Ca 3 (PO 4) 2 host, and its phase structure, morphology features and optical properties were systemically investigated. The as-prepared SCLP: Eu2+ phosphor had a monoclinic symmetry and a broad green emission from 420 to 730 nm with a quantum yield as high as 77%. The SCLP host offered five types of Sr2+ ions sites for Eu2+ ions occupation; and the PL spectra were divided into three sub-peaks locating at 501 (19960.08 cm−1), 527 (18975.33 cm−1) and 566 nm (17667.84 cm−1), which were proved to the emission of Eu2+ ions at the nine-coordinated Sr(1, 3, 5)O 9 , eight-coordinated Sr(2)O 8 and special vacant Sr(4)O 6 sites, respectively. The thermal stability was improved through the package of SiO 2 , and the activation energy was enhanced from 0.1098 to 0.1457 eV. Eventually, the SCLP: x Eu2+ phosphors were applied in white light-emitting diode, showing high color rendering index (Ra = 94.4 and R9 = 81.7) and moderate correlated color temperature (CCT = 4902 K). This work could help to understand the mechanism behind the site-controlled activator emission and offer some meaningful ideas to design a new whitlockite phosphor with desirable spectral emission for application in high quality lighting source. [ABSTRACT FROM AUTHOR]

Optical thermometry and white light-emitting diodes (WLEDs) are the research hotspots for Eu3+ doped phosphors. In this study, a series of Sr 2 TiSi 2 O 8 : Eu3+ red phosphors were developed in a solid-state reaction method. The luminescent properties of the Sr 2 TiSi 2 O 8 : Eu3+ phosphor illustrate that Sr 2 TiSi 2 O 8 : Eu3+ is effectively excited by the NUV LED chip and emit an intense red light with a peak of 618 nm due to the noninversion symmetry coordination of Eu3+ in Sr 2 TiSi 2 O 8. The local coordination environment of Eu3+ was investigated in detail using crystallographic data, spectroscopic data and Judd–Ofelt parameters. In addition, the emission intensity of Sr 2 TiSi 2 O 8 :Eu3+ is extremely sensitive to temperature. The relative sensitivity of Sr 2 TiSi 2 O 8 :Eu3+ is 1.1% k-1@300 k, which is comparable to other Eu3+-activated temperature sensing materials. The possible mechanism of the temperature sensitive quenching characteristics was proposed. The results indicate that Sr 2 TiSi 2 O 8 :Eu3+ is a potential temperature sensing material. [ABSTRACT FROM AUTHOR]

Developing phosphors with narrow band emission and excellent performance is the main goal of current leading research. In this study, a novel narrow band blue-emitting phosphor Rb 2 ZrSi 3 O 9 : Eu2+ was prepared that can be fully excited by near ultraviolet (NUV) light, emits a bright blue light peak at 470 nm, and has a full width at half maximum (FWHM) of 60 nm. The synthesized Rb 2 ZrSi 3 O 9 : Eu2+ had excellent photoluminescence properties that were reflected in its good thermal stability (up to 82%) and high internal quantum efficiency (up to 75%). These remarkable luminescence properties were mainly ascribed to the highly symmetric and dense crystal structure composed of [Si 3 O 9 ]6- ring pairs. Multiple emission centers in the Rb 2 ZrSi 3 O 9 : Eu2+ phosphor were confirmed through the photoluminescence (PL) spectra and time-resolved (PL) spectra. A bright warm WLED device with a low correlated color temperature (3386 K) and high color-rendering index (CRI~89.3) was produced by combining the blue phosphor with (Sr, Ba) 2 SiO 4 : Eu2+ and CaAlSiN 3 : Eu2+ and NUV (380 nm). The results indicate that Rb 2 ZrSi 3 O 9 : Eu2+ could be a promising phosphor for use in WLEDs. [Display omitted] [ABSTRACT FROM AUTHOR]

As is well known, whitlockite β -Ca 3 (PO 4) 2 -type phosphors are easily evolved to a new crystal structure by cation substitution, and have various crystallographic sites for doping activators to achieve luminescence. Herein, a novel broadband emitting Sr 8 MgIn(PO 4) 7 : Eu2+ (SMIP) phosphor was prepared by high temperature solid state reaction. Its crystal structure was analyzed and refined via the Rietveld refinement method. The SMIP crystal presents a monoclinic system with space group C2/m. Their diffuse reflection and excitation spectra both show an intense absorption to the wavelength of 250–500 nm. And the photoluminescence spectrum exhibits a strong broadband emitting from 450 to 800 nm. Moreover, the luminescence decay curves reveal three kinds of Sr/Mg2+ crystallographic sites for Eu2+ occupying in SMIP host. For SMIP: xEu2+ samples, the optimized doping concentration was determined to be 0.03, and the energy transfer among the nearest-neighbor was dominating. Further, the activation energy was estimated to be 0.1145 eV. Finally, white light-emitting diodes (WLED) lamps were fabricated by coating the mixtures of SMIP: 0.03Eu2+ phosphors and BaMgAl 10 O 17 : Eu2+ phosphors on the surface of 400 nm near-ultraviolet chip. The optimized WLED lamp exhibits a correlated color temperature of 3034 K and a good color rendering index of 91.7. These results demonstrate the commercialized prospect of SMIP: Eu2+ materials as a broadband orange phosphor for application of solid state lighting. [Display omitted] • The Sr 8 MgIn(PO 4) 7 :Eu2+ phosphor displays a novel broadband orange-yellow emitting from 450 to 800 nm. • Three kinds of Sr/Mg2+ crystallographic sites for Eu2+ occupying in SMIP host were revealed by the luminescence decay curves. • The optimized WLED lamp exhibits a correlated color temperature of 3034 K and a good color rendering index of 91.7. [ABSTRACT FROM AUTHOR]