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Despite extensive research on the photoluminescence properties of Bi3+ ions, the origins of their emission and excitation bands remain elusive. Herein, we present a comprehensive analysis of the photoluminescence properties of Bi3+-activated LuXnGaO4 (Xn = Mg, Zn), elucidating the underlying factors governing the intra-ionic and extra-ionic electronic transitions. By integrating crystal structure data and spectroscopic data analyses with semi-empirical formula calculations, the origins of excitation and emission states were elucidated. Moreover, the impact of alterations in chemical surroundings on the luminescence of Bi3+ was investigated. Both LuXnGaO4:Bi3+ phosphors exhibit three excitation peaks in the near ultraviolet region and display a broadband yellow emission. However, the luminous behavior of LuMgGaO4:Bi3+ and LuZnGaO4:Bi3+ differs due to variations in the band gap, bond length and neighboring atoms. It is anticipated that the investigation of Bi3+-activated gallates presents a promising avenue for advancing wide-band and long-wavelength emitting phosphors. [ABSTRACT FROM AUTHOR]

It is of great significance to achieve precise luminescence regulation of Bi3+-activated phosphor by adjusting crystallographic environment of Bi3+ ions. In this study, a series of Bi3+ activated melilite-structure gallate ABGa 3 O 7 (A = Ca, Sr, Ba; B = La, Gd) phosphors was successfully synthesized via solid-state reaction method. Using SrGdGa 3 O 7 :Bi3+ as a representative, the crystal structure and photoluminescence properties were studied. The emission of ABGa 3 O 7 :Bi3+ adjustable from blue to cyan light can be reached by replacing A and B atoms. The structural characteristics of ABGa 3 O 7 were explored using geometry optimization calculations and Rietveld refinement. The relations between the transformation of Bi3+ environment and the luminescence behavior are deduced by combining theoretical calculations and experimental results. The results show that the contraction, broadening and shift of excitation and emission spectra of ABGa 3 O 7 :Bi3+ depend on the bond length and distortion of polyhedra as well as the number of luminous centers. It is hoped that this study can provide some insights for the development and modification of a novel Bi3+ activated gallate phosphors. [ABSTRACT FROM AUTHOR]

Developing an efficient broadband yellow phosphor with more red-light components and small thermal quenching is of great significance for solid-state lighting. In this study, a broadband yellow-emitting nitridoalumosilicate Ca 4 SiAl 3 N 7 :Ce3+ phosphor was successfully synthesized by a solid-phase method at comparatively low temperature (1350 °C) and normal pressure. The crystal structure and electronic structure of Ca 4 SiAl 3 N 7 were studied using Rietveld refinement and density functional theory. The photoluminescence properties of the Ca 4 SiAl 3 N 7 :Ce3+ phosphor were studied, including excitation and emission spectra, time-resolved photoluminescence spectra and temperature-dependent emission spectra. The results show that the Ca 4 SiAl 3 N 7 :Ce3+ phosphor can be effectively excited by the blue chip and emit a strong broadband yellow light with maximum at 568 nm and the half width of 142 nm. Moreover, the Ca 4 SiAl 3 N 7 :Ce3+ phosphor exhibits good thermal stability, which can still maintain 75% and 68% of the strength at room temperature when at 150 °C and 200 °C, respectively, and without spectral shift. A warm WLED can be realized by combining Ca 4 SiAl 3 N 7 :Ce3+ yellow phosphor and blue LED chip. This study provides insights into developing novel broadband yellow nitridoalumosilicate phosphor with more red-light components, small thermal quenching and simple synthesis conditions. [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]

Developing a yellow phosphor with broadband emission covering more red‐light areas is an effective approach to achieve high‐quality solid‐state lighting. In this study, a novel yellow‐emitting nitride phosphor, Ca5Si2Al2N8:Ce3+, was successfully prepared at atmospheric pressure and lower temperatures (1300°C), and its structure‐property relation was revealed using crystal refinement, photoluminescence (PL) spectra, time‐resolved PL spectra, and density‐functional theory calculations. The results demonstrate that Ca atoms occupy three different crystallographic sites in the lattice, which are substituted by Ce3+ to form multiple luminescence centers. Thus, Ca5Si2Al2N8:Ce3+ emits strong yellow light with a maximum peak at 585 nm and a wide emission band. Compared with YAG:Ce3+, Ca5Si2Al2N8:Ce3+ has a wider emission band with a FWHM of 150 nm, which can effectively cover the green and red areas. Moreover, the sample can be fully excited by a blue LED chip due to its broad excitation band. Notably, the Ca5Si2Al2N8's tight crystal structure composed of edge‐sharing AlN4 and SiN4 tetrahedra pairs guarantee its thermochemical stability and quantum efficiency. Furthermore, Ca5Si2Al2N8:Ce3+ exhibits better thermal stability than YAG:Ce3+. The results indicate that Ca5Si2Al2N8:Ce3+ is a promising yellow phosphor for WLEDs. [ABSTRACT FROM AUTHOR]

The systems of Si-Al-O-N originated from the outstanding nitrogen ceramic of Si 3 N 4 have received considerable attention due to their significant luminescence properties. In this work, to explore its potential in the full-spectrum lighting applications, a novel oxynitride based phosphor Lu 4 SiAlO 8 N: Ce3+ was investigated in detail by using the Rietveld refinement, DFT calculations, photoluminescent (PL) and time-resolved PL (TRPL) spectra. The results indicate that Lu 4 SiAlO 8 N performs a tight host lattice formed by the edge-sharing LuO 6 polyhedrons and (Si, Al) (O, N) 4 tetrahedrons; the multiple crystallographic Lu3+ sites in the host lattice contribute to the broad emission band. Under the near ultraviolet (NUV) light excitation, Lu 4 SiAlO 8 N: Ce3+ emits a bright cyan light peaked at 470 nm, and its full width at half maximum (FWHM) can reach 120 nm, which well replenishes the "cyan cavity". Moreover, the energy transfer between the multiple luminescent centers was verified through the TRPL spectra. The temperature-dependent spectra of Lu 4 SiAlO 8 N: Ce3+ was measured to prove its acceptably thermal stability. All the results indicate the Lu 4 SiAlO 8 N: Ce3+ to be a promising candidate for the application in WLEDs. A broad-band cyan light emission has been achieved in Ce3+-activated oxynitride Lu 4 SiAlO 8 N. Image 1 [ABSTRACT FROM AUTHOR]

The exploration of rare-earth-free phosphors is desirable for white LEDs applications. In this work, Cr3+ doped Na 2 TiSiO 5 self-activated phosphors were synthesized by conventional solid-state reaction. The electronic structure of Na 2 TiSiO 5 was calculated using density functional theory (DFT) methods. The variations in crystal structure, luminescence properties and thermal stability of Na 2 Ti 1-x SiO 5 : x Cr3+ were exhaustively investigated by the analysis of XRD patterns, photoluminescence (PL) spectra, diffuse reflection spectra, PL decay curves and temperature-dependent PL spectra. Owing to the red shift of absorption edge and energy transfer between Cr3+ ions and Ti4+ ions, the emission intensity and thermal stability of Na 2 TiSiO 5 were improved by the introduction of Cr3+ ions, and the peak position was red-shifted. The results indicate that the introduction of Cr3+ ions could be an effective method to regulate the luminescence of Ti4+-activated oxide phosphors. • The electronic structure of Na 2 TiSiO 5 was calculated using DFT methods. • The doping of Cr3+ ion can effectively regulate the luminescence of Na 2 TiSiO 5 phosphor. • The improvement in thermal stability is attributed to the energy transfer between Cr3+ and Ti4+. [ABSTRACT FROM AUTHOR]

A novel pale‐yellow Ba2ZnGe2O7:Bi3+ phosphor with site‐selected excitation and small thermal quenching was synthesized by conventional solid‐state sintering. The crystal structure and luminescence properties have been investigated in detail for the first time using XRD patterns, photoluminescence spectra, diffuse reflection spectra, decay curves, and temperature‐dependent emission spectra. The results reveal that the excitation spectrum of Ba2ZnGe2O7:Bi3+ phosphor locates in the near‐ultraviolet region of 300‐400 nm, and its emission shows an obvious site‐selective excitation phenomenon since Bi3+ ions occupy two different crystallographic sites in the Ba2ZnGe2O7 host. When excited under 360 nm, the phosphors show a pale‐yellow emission in the range of 400‐700 nm with the maximum peaking at 520 nm, while when excited under 316 nm, the phosphors show a blue emission in the range of 400‐700 nm with the maximum peaking at 480 nm. In addition, the emission of Ba2ZnGe2O7:Bi3+ can also be easily controlled by changing the Bi3+ concentration. The Ba2ZnGe2O7:Bi3+ phosphor has small thermal quenching, and its emission intensity only decreases by 2% at 200°C. The results indicate that this novel pale‐yellow Ba2ZnGe2O7:Bi3+ phosphor could be conducive to the development of white light‐emitting diodes. [ABSTRACT FROM AUTHOR]

Rare earth doped lithium containing nitridosilicates have become a hot spot in phosphors research because of their excellent luminescent properties. Here, the nitridolithosilicate Li 2 SrSi 2 N 4 :Eu 2+ was successfully synthesized by solid-state reaction. Li 2 SrSi 2 N 4 :Eu 2+ shows a red emission at 615 with an FWHM = 100 nm at the excitation of the near ultraviolet spectral region. Rietveld refinement on the powder XRD pattern revealed that Li 2 SrSi 2 N 4 crystallizes in the cubic space group Pa3̄ (no. 205) [Z = 12, a = 10.7242(3) Å, V = 1233.37(9) Å 3 ] and exhibits a three-dimensional network with solely vertex-sharing [SiN4] tetrahedral. The electronic structure of Li 2 SrSi 2 N 4 was explored using density functional theory (DFT) methods. The results show that Li 2 SrSi 2 N 4 :Eu 2+ can benefit the development of the novel red luminophor. [ABSTRACT FROM AUTHOR]

[Display omitted] • LiScSiO 4 :Ce3+, Tb3+ exhibit high relative sensitivity and excellent signal discriminability. • LiScSiO 4 :Ce3+, Tb3+ exhibit outstanding temperature resolution and efficient emission at high temperatures. • LiScSiO 4 :Ce3+, Tb3+ exhibits excellent visualizing thermochromic and recovery properties. Developing optical thermometer phosphors with high sensitivity, high signal discriminability and strong fluorescence intensity is ongoing. A dual-emitting thermochromic phosphor, LiScSiO 4 :Ce3+, Tb3+, was successfully synthesized via solid-state reaction method. The crystal structure, electronic structure, luminescent performance and thermal luminescence behaviors as well as the luminescence mechanism of LiScSiO 4 :Ce3+, Tb3+ were systematically investigated. Due to the energy transfer and different thermoluminescence behaviors between Ce3+ and Tb3+, high relative sensitivity (2.2 % K−1@473 K), excellent signal discriminability (5747 cm−1), outstanding temperature resolution (0.067 K) and good repeatability, as well as efficient emission at high temperatures were achieved based on the fluorescence intensity ratio of Ce3+ and Tb3+, indicating its potential in ratiometric optical thermometer. Moreover, the excellent visualizing thermochromic enable LiScSiO 4 :Ce3+, Tb3+ to be used as safety sign in variable temperature environment to monitor temperature distribution. [ABSTRACT FROM AUTHOR]

The undoped and Eu 2+ /Ce 3+ doped Ca 3 Li 4-y Si 2 N 6-y O y (0≤y≤1.5) (CLSN) were successfully prepared by solid-state reaction and their luminescence properties were studied. The undoped CLSN shows red defect-related luminescence with maximum emission intensity at 710 nm, Eu 2+ and Ce 3+ doped CLSN also show red emission centered at 702 nm and 673 nm, respectively. The electronic structure and the thermal stability of CLSN were investigated in this work. The results indicate that CLSN:Eu 2+ /Ce 3+ could be conducive to the development of phosphor-converted light-emitting diodes. [ABSTRACT FROM AUTHOR]

A near-UV excited phosphor, LiSr4(BN2)3:Eu2+ (LSBN:Eu2+), was synthesized using a solid-state reaction at 800 °C. The crystal structure of LSBN had been refined and determined from the XRD profiles by the Rietveld refinement method, which belongs to the space group Im3̅m with the lattice constants a = b = c = 7.46112(23) Å. The excitation spectra of the LSBN:Eu2+ phosphors were centered at around 370 nm and covered the range from 300 to 450 nm. Under 400 nm excitation, the emission spectra of the LSBN:Eu2+ phosphors show a red emission centered at about 640 nm (FWHM ≈ 130 nm). And the energy transfer between the Eu2+ ions is confirmed to arise from the electric dipole–dipole interactions. The nontypical emission blue-shift in the single luminescence center with increasing temperature luminescence properties is also investigated. The results indicate that LSBN:Eu2+ could be conducive to the development of white light emitting diodes. [ABSTRACT FROM AUTHOR]

Li0.995− xMg xSi2− xAl xN3: Eu2+0.005 ( LSN: xM) (0 ≤ x ≤ 0.04) phosphors were successfully synthesized by gas-pressed sintering. Double substitution which is partial replacement of (LiSi)5+ with (MgAl)5+ is presented as a useful way to improve luminescence properties. With an increase in the substitution concentration, the intensity of the emission band of LSN: xM was enhanced and the peak position shows blue shift due to the decreased stokes shift. Furthermore, LSN: xM (0 ≤ x ≤ 0.04) shows narrower full width at half maximum and higher thermal stability than Li0.995Si2N3: Eu2+0.005. [ABSTRACT FROM AUTHOR]

Using the solid-state reaction method, Ce3+, Tb3+-coactivated Si5 AlON7 ( Si6− z Al z O z N8− z, z = 1) phosphors were successfully synthesized. The obtained phosphors exhibit high absorption and strong excitation bands in the wavelength range of 240-440 nm, matching well with the light emitting-diode ( LED) chip. The ET from Ce3+ to Tb3+ ions in Si5 AlON7: Ce3+, Tb3+ has been studied and demonstrated by the luminescence spectra and decay curves. Moreover, the phosphors show tunable emissions from blue to green by tuning the relative ratio of the Ce3+ to Tb3+ ions. Thermal quenching properties of Si5 AlON7: Ce3+, Tb3+ had also been investigated and the quenching temperature is ~190°C. These results show that Si5 AlON7: Ce3+, Tb3+ could be a promising candidate for a single-phased color-tunable phosphor applied in UV-chip pumped LEDs. [ABSTRACT FROM AUTHOR]

The photoluminescence behaviors of bismuth-activated phosphors are fascinating and puzzling due to the existence of multi-type electronic transitions. Therefore, the development of novel bismuth-activated phosphors is an important objective of many researchers. In this work, a marvellous photoluminescence characteristic of Bi3+ ion was observed in a cubic phase of Y 3 TaO 7 (YTO), which performs multi-color light emissions, although there is only one cationic crystallographic site for accommodating Bi3+ dopant. Under near-ultraviolet (NUV) light excitation, Bi3+-activated YTO produces a considerably wide cyan light peaked at 477 nm with a full width at half maximum (FWHM) of 130 nm. Moreover, with the increase of excitation wavelength, the emission band was detected to have an extraordinary red shift from 477 to 547 nm and broadening, and its FWHM reaches up to 160 nm. Combined with the crystal and electronic structure of YTO, an interpretation was proposed to shed light on the photoluminescence behavior of Bi3+ ion in this system, which indicates that multi-type electronic transitions are supposed to produce the surprising luminescence properties of Bi3+ ion. The detailed discussion was processed in this work, which is expected to enhance people's comprehension for the luminescence behavior of Bi3+ ion. Multi-type electronic transitions induced multi-color light emitting of Bi3+ ion have been realized in tantalate.[ [Display omitted] ] [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]

Na2TiSiO5 (NTSO) is prepared by firing stoichiometric amounts of NaOH, TiO2, and SiO2 (Al2O3 crucible, 850 °C, 4 h). [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]

[Display omitted] • The SCXP host with multiple cation sites was successfully designed. • Their structural evolution and optical properties were systemically studied. • The relation between site occupation and luminescence was revealed. • The neighboring-cation-size could control the distribution of activator. • A high color rendering WLED was fabricated via these phosphors. The photoluminescence behavior in a multiple cation lattice host for obtaining desired spectral emission is an important scientific question to develop next-generation high quality lighting sources. However, how to manipulate the distribution of rare-earth activators over various cation sites is still a technical challenge. Herein, for the first time, trivalent ions Al3+ and Ga3+ were introduced to β -Ca 3 (PO 4) 2 -kind host for preparing the new isostructural Sr 8 CaAl(PO 4) 7 (SCAP) and Sr 8 CaGa(PO 4) 7 (SCGP) hosts and controlling the incorporation of activators Eu2+ in the M(4) sites. Their structural evolution, morphology, diffuse reflection spectrum, electron structure and luminescent properties were systemically investigated. The emission of Eu2+ ions distributed over the nine-coordinated Sr(1, 3, 5)O 9 , eight-coordinated Sr(2)O 8 and special coordinated Sr(4)O 6 sites was located in the green (507 nm), yellow (555 nm) and red (610 nm) regions, respectively. Further, a smaller cation radius (Al3+) allowed higher number of activators (Eu2+) to be accessed to the neighboring M(4) lattice site for obtaining more intense red emission, which would enable these kinds of phosphors-converted white light emitting diodes to show quite high color-rendering indexes (Ra = 94.4). This neighboring-cation-size strategy mentioned here can become a novel approach to PL spectral modulation through controlling the distribution of Eu2+ activators over various lattice sites for excellent solid state lighting. [ABSTRACT FROM AUTHOR]

Samples of CaSr2Al2O6:xCe3+,xLi+ (0.01 ≤ x ≤ 0.09) and CaSr2Al2O6:0.03Ce3+,0.03Li +,yMn2+ (0 ≤ y ≤ 0.07) are prepared by solid state reactions of CaCO3, SrCO3, Al2O3, CeO2, and MnCO3 (alumina crucibles, 10%H2/N2, 1400 °C, 6 h). [ABSTRACT FROM AUTHOR]