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Whitlockite-type structure phosphors have been widely studied due to their adjustable chemical composition and abundant crystal location. Whitlockite-type phosphors can be doped with rare earth elements to achieve the emission of warm white light. White light-emitting diodes (w -LEDs) have become increasingly popular and play a significant role in many applications, such as Biosensing and fluorescent labeling. In this work, The Ca 2.6 K 0.2 La 0.2 (PO 4) 2 (CKLP) whitlockite-type phosphors co-doped with Dy3+ and Sm3+ were entered via a high-temperature solid-phase reaction. Their crystal structure, luminescence characteristics, and temperature sensitivity were explored in detail. Through doping Dy3+ and Sm3+, can obtain white light and warm white light. As the concentration of Sm3+ increased, their lifetime decreased from 0.483 ms to 0.059 ms, confirming interionic energy transfer in the host. The CKLP: 0.06Dy3+, 0.06Sm3+ phosphor prepared by Fluorescence Intensity Ratio (FIR) technology has suitable temperature sensing performance. Its relative sensitivity (Sr) and complete sensitivity (Sa) are high up to 4.48 × 10−3 k−1 and 1.021%K−1 at 298 K. The results show that CKLP: Dy3+ and Sm3+ phosphors used in w -LEDs and display devices will present excellent application potential in new optical thermometry. • The whitlockite-type structure phosphor realized white light emission. Obtained excellent color temperature coordinates, high sensitivity and realized the control of warm white light. • The whitlockite-type structure phosphors are a candidate material for non-contact optical temperature sensing and have potential anti-counterfeiting applications. [ABSTRACT FROM AUTHOR]

Following the rapid growth of lightning technology, the development of red-emitting phosphors is effective for improving color temperature and color rendering index for w-LEDs devices. Herein, a single phased garnet phosphor with cation and polyhedron substitution modification was firstly prepared. For Mg 3 Gd 2 Ge 3 O 12 : Bi3+, Eu3+, the intensity has been remarkably improved by about 16% compared to the one without Bi3+ sensitization. The energy transfer mechanism is identified in this work. Based on cation and polyhedron substitution strategies, novel phosphors with different compositions were obtained and further modified the PL properties. With Lu3+ substitution, the bond lengths between Bi3+ ion and anion ligands are decreased and the site symmetry has been strengthened, which leads to a 21 nm blue shift when Lu3+ totally replaced Gd3+ ions. In addition, Lu3+ and [SiO 4 ] substitution strategies both effectively increased symmetric rigid structure, which leads to a significant improvement in thermal stability, indicating the samples own great potential in optical applications This work provides a new insight to synthesis red-emitting phosphors for warm white-LEDs. [ABSTRACT FROM AUTHOR]

Ca9La(PO4)5(SiO4)F2:Tb3+,Dy3+ (CLPSF:Tb3+,Dy3+) phosphors were successfully prepared using the traditional solid‐state technique. The crystal structure was refined and the luminescence properties have been examined in detail. The band gap and electronic structure of Ca9La(PO4)5(SiO4)F2 were performed by the periodic density functional theory (DFT) calculation. The spectral and fluorescence decay dynamics of CLPSF:Tb3+,Dy3+ show that the energy transfer behavior between Tb3+ and Dy3+ ions is observed. The CLPSF:Tb3+,Dy3+ phosphors can be efficiently excitable at the wavelengths range from 300 to 500 nm. The emission spectrum covers the whole visible part of the spectra with the sharp emission bands in red, green, and blue regions. The correlated color temperature (CCT) and color rendering index (CRI) of white light emission could be improved by the fine‐tuning of the Tb3+ and Dy3+ ions ration in accordance with the energy transfer behavior. Thus, the CLPSF:Tb3+,Dy3+ phosphor could be used as a material for the near‐ultraviolet (n‐UV) and white light‐emitting diodes (w‐LEDs). [ABSTRACT FROM AUTHOR]

A novel orange-red emitting orthosilicate phosphor LiGd 9 (SiO 4) 6 :Mn2+ (LGS:Mn2+) belongs to hexagonal lattice with P 6 3 / m space group was synthesized via solid-state method and the phase composition, crystal structure as well as luminescence properties were examined for potential application in near ultraviolet (n -UV) pumped white light emitting diodes (w -LEDs). The as-prepared LGS:Mn2+ phosphor exhibits three excitation bands peaked at 273, 312 and 410 nm, which corresponds to the transitions of Gd3+ from ground state 8S 7/2 to 6I 7/2 , 6P 7/2 and Mn2+ from ground state 6A 1 (6S) to the individual components of the multiplets [4A 1 (4G), 4E(4G)], respectively. Upon excitation at 312 nm, the phosphors display an intense broad orange-red emission peaked around 594 nm, which ascribed to the typical spin-forbidden transition (4T 1 (4G)-6A 1 (6S)) of the Mn2+ ions. The concentration quenching mechanism and average separation distance in conjunction with fluorescence decay times of Mn2+ ions in LGS:Mn2+ phosphor were discussed. The indispensable parameters for application in n -UV high-powered w -LEDs, such as the thermal quenching of photoluminescence and internal quantum efficiency of LGS:Mn2+ phosphor, have also been investigated in detail. The above results indicate that LGS:Mn2+ could play a key role as an orange-red emission for potential application in n -UV-based w -LEDs. • LiGd 9 (SiO 4) 6 O 2 :Mn2+ luminescent materials were synthesized successfully. • This phosphor have excellent thermal stability and emission efficiency. • High energy transfer efficiency could be obtained between Gd3+ and Mn2+ ions. [ABSTRACT FROM AUTHOR]

Highlights • The ET mechanism has been confirmed by the luminescence spectra and fluorescence decay curves. • The ET interaction mechanism was determined to be dipole–quadrupole interaction. • The emission color of as-prepared phosphor could be adjusted from green to yellow. Abstract The Ca 9 La(PO 4) 5 (SiO 4)F 2 :Tb3+,Sm3+ phosphor with apatite structure has been successfully synthesized by high temperature solid-state reaction, and its luminescence properties as well as energy transfer mechanism has been investigated in detail. The energy transfer (ET) efficiency increases with increasing Sm3+ doping content, that was confirmed by the luminescence spectra and fluorescence decay curves of corresponding ions. The ET interaction mechanism was determined to be dipole–quadrupole interaction. The emission color of Ca 9 La(PO 4) 5 (SiO 4)F 2 :Tb3+,Sm3+ phosphor could be adjusted from green (0.272, 0.489) to yellow (0.363, 0.395) area through controlling the dopant ratio of Tb3+/Sm3+. The above results indicate that the Ca 9 La(PO 4) 5 (SiO 4)F 2 :Tb3+,Sm3+ phosphor has a great potential in white light-emitting diodes application. [ABSTRACT FROM AUTHOR]

Abstract A series of novel luminescence phosphors Ca 9 La(PO 4) 5 (SiO 4)Cl 2 : x Eu2+ (CLPSCl:Eu2+) with apatite structure have been synthesized by a high temperature solid-state reaction. The phased purity of as-prepared phosphors was verified through XRD technique. For further discussion, a series of analysis were performed such as the photoluminescence emission and excitation spectrum and decay lifetime to identify the luminescent properties of CLPSCl:Eu2+ phosphors. The CLPSCl:Eu2+ displays broad excitation spectra ranging from 250 to 450 nm, and intends emission intensity at 461 nm under 345 nm. The optimum Eu2+ concentration of CLPSCl is 8 mol%. The luminescence decay lifetime of the optimum phosphors was measured to be 275 ns. All of the results obtained highly indicate that CLPSCl:Eu2+ is potentially blue-emitting phosphor for application in white LEDs. [ABSTRACT FROM AUTHOR]

Abstract The novel apatite-type phosphor Ca 9 Tb(PO 4) 5 (SiO 4)F 2 :Mn2+ (CTPSF:Mn2+) has been successfully synthesized and it demonstrated a potential for optical thermometry. The energy transfer process between Tb3+ and Mn2+ was of resonant type via a dipole-dipole mechanism based on the Inokuti–Hirayama theoretical model, and the energy transfer (ET) efficiency and ET rate were estimated. In view of the energy transfer behavior, a strategy, involving the use of Tb3+ and Mn2+ dual-emitting centers with different thermal quenching behavior, has been developed to achieve temperature sensitivity and good signal discrimination. The temperature dependence of the fluorescence intensity ratios (FIR) for the dual-emission bands peaking at 548 and 595 nm was studied in the range of 298–573 K under excitation of 377 nm ultraviolet light and the maximum relative sensitivity was approximately 1.92% K−1 at 423 K. It is expected that this preliminary study will provide an important advance in exploring novel ratiometric optical thermometry. Highlights • Novel apatite-type phosphor Ca 9 Tb(PO 4) 5 (SiO 4)F 2 was synthesized. • Energy transfer mechanism is estimated based on Inokuti–Hirayama model. • Non-contact thermometry was developed with a new inorganic material. • The maximum S r of the as-prepared phosphor was as high as 1.92% K−1. • This work provides an insight to design ratiometric optical thermometry. [ABSTRACT FROM AUTHOR]

Whitlockite-type structure phosphors have received extensive attention and research due to their adjustable chemical compositions in isomorphic compounds and providing rich crystal positions for doping activators. Ca 2.6 K 0.2 La 0.2 (PO 4) 2 whitlockite-type phosphors with Dy3+ singly doping and Dy3+, Eu3+ co-doping were prepared via high temperature solid-phase reaction, and the crystallographic characteristics, luminescence properties and temperature sensing performance were investigated in detail. The prepared phosphors are pure phase and both Dy3+ and Eu3+ enter into the matrix and produce blue, yellow and red emissions. The CCT values of the emitted light from Ca 2·6 K 0·2 La 0·2 (PO 4) 2 : Dy3+, Eu3+ phosphors increase with the Eu3+ concentration rises, changing from cold white light to warm white light. The integrated emission intensity of Dy3+ in the phosphor decreases with the change in the doping ratio of Dy3+ and Eu3+, causing by the energy transfer from Dy3+ to Eu3+. The Ca 2·6 K 0·2 La 0·13 (PO 4) 2 :0.06Dy3+, 0.01Eu3+ phosphor shows temperature sensing performance based on FIR technique, with the maximum relative sensitivity calculated to be 0.181% K−1. All the results reveal that the Ca 2·6 K 0·2 La 0·2 (PO 4) 2 : Dy3+, Eu3+ phosphors can be applied to w-LEDs and display devices, and can be used as a new type of optical thermometer. Dy3+/Eu3+ co-doped Ca 2·6 K 0·2 La 0·2 (PO 4) 2 phosphor applied for w-LEDS and temperature sensing. [Display omitted] • Single-phase luminescent materials Dy3+, Eu3+ co-doped Ca 2·6 K 0·2 La 0·2 (PO 4) 2 phosphor with whitlockite structure was synthesized for the first time. • The concentration quenching and energy transfer mechanisms were investigated. • The emission color of Ca 2·6 K 0·2 La 0·2 (PO 4) 2 : Dy3+, Eu3+phosphors changes from natural white light to warm white light with the increase of Eu3+ concentration. • The samples showed temperature sensing performance with maximum S a to be 2.06 × 10−3 K−1 and S r to be 0.181% K−1 under 303 K. [ABSTRACT FROM AUTHOR]

A novel apatite structure phosphor Ca 9 La(PO 4 ) 5 (GeO 4 )F 2 :Dy 3+ (CLPGF:Dy 3+ ) with a hexagonal lattice in the P 6 3 / m space group was synthesized via a facile solid state technique. The crystal and fine local structure as well as their photoluminescence properties were investigated in detail. The CLPGF:Dy 3+ phosphor can absorb in the UV-vis spectral region of 290–475 nm and exhibit two intense emission bands centered at 485 and 580 nm, which ascribes to 4 F 9/2 → 6 H 15/2 and 4 F 9/2 → 6 H 13/2 transitions of Dy 3+ , respectively. The concentration quenching of Dy 3+ emission occurs via the energy transfer among the nearest-neighbor ions and the corresponding quenching mechanism was verified to be the dipole-dipole interaction. The quantum efficiencies of the phosphors were examined to be 72.9% and its luminescence intensity at 150 °C decreases to 93.8% and 98.6% of the initial value at room temperature, which corresponds to 4 F 9/2 to 6 H 15/2 transition and 4 F 9/2 to 6 H 13/2 transition of Dy 3+ ions, respectively. Their interesting photoluminescence properties indicate that the CLPGF:Dy 3+ phosphor is a promising white-emitting candidate for w -LEDs applications. [ABSTRACT FROM AUTHOR]

The simple high-temperature solid-state route was adopted to synthesize a series of related Ba 3 LaK(PO 4 ) 3 F: x Eu 2+ (BLKPF: x Eu 2+ ) blue phosphors. The photoluminescence (PL) and diffuse reflection spectra have been investigated in detail. These phosphors which can be well excited by the 388 nm near ultraviolet light, produce the emitted blue light peaks located at about 460 nm. The critical Eu 2+ concentration quenching mechanism was ascribed to the dipole–dipole interaction, and the optimum concentration was eventually proved to be 0.1 mol. All above results indicate that Ba 3 LaK(PO 4 ) 3 F: x Eu 2+ phosphor can act as an appropriate candidate of the blue phosphor in the future. [ABSTRACT FROM AUTHOR]

A series of Dy3+-doped MGd 9 (SiO 4) 6 O 2 :Dy3+ (M = Li, Na, K) phosphors that generated white emission were prepared using the high temperature solid-state technique. Simultaneously, the phase composition, crystal structure, electronic structure, as well as the luminescence properties of the as-prepared phosphors were investigated in detail. The structural refinement showed that the MGd 9 (SiO 4) 6 O 2 crystallized with the hexagonal apatite-type structure. The unit cell parameters increased gradually and the main peaks of the samples in XRD patterns shifted towards high angles with the substitution of alkali-metal ions (from Li+ to K+). Under the excitation of 350 nm, the as-obtained MGd 9 (SiO 4) 6 O 2 :Dy3+ phosphors gave bright white emission with the major emission peaks centering at 454, 477 and 573 nm. And the R y/b , CIE chromaticity coordinate and the corrected color temperature (CCT) of the phosphors were adjusted from 0.96, (0.3256, 0.3625) and 4602 K to 1.13, (0.3369, 0.3582) and 4201 K attributing to the substitution in the crystal structure. The thermoluminescence study of MGd 8.90 (SiO 4) 6 O 2 :0.10Dy3+ (M = Li, Na, K) showed good stability and the decay lifetimes of the samples were estimated to be about 470 μs. All the results suggested that the luminescence properties could be modified by the substitution of alkali metal ions, and the MGd 9 (SiO 4) 6 O 2 :Dy3+ (M = Li, Na, K) phosphors have potential application as white emission candidate for w -LEDs. • Novel Dy3+ doped apatite structure phosphors were successfully synthesized. • The symmetrical environment could be modified to a certain extent owing to substitution of alkali metal ions. • The DFT calculation was used to check the electronic structure. [ABSTRACT FROM AUTHOR]

An appropriate solid-state route was adopted to synthesize a series of related Ba 3 Sc(PO 4 ) 3 : x Sm 3+ red-orange phosphors. The Rietveld method was used to explore the structure of the phosphor. At present the PL, PLE, diffuse reflection and decay curves have been investigated in detail. These phosphors can be accurately excited by the 406 nm n-UV light and produce the emitted red-orange light whose peaks locate at about 566 nm, 603 nm and 650 nm. The quantum efficiency of Ba 3 Sc 0.95 (PO 4 ) 3 :0.05Sm 3+ was 53.5%. All above results indicate that Ba 3 Sc(PO 4 ) 3 :Sm 3+ phosphor can act as a suitable candidate of the warm components of n -UV w-LEDs. [ABSTRACT FROM AUTHOR]

Ba 3 Sc(PO 4 ) 3 :Eu 2+ ,Tb 3+ (BSP:Eu 2+ ,Tb 3+ ) phosphors were successfully prepared via conventional high-temperature solid-state reaction, their luminescence properties as well as energy transfer mechanism have been investigated in detail. The energy transfer mechanism was proposed to be the dipole–quadrupole mechanism, and the energy transfer efficiency was also estimated. BSP:Eu 2+ ,Tb 3+ phosphors showed a broad emitting band centered at 518 nm and several sharp emission peaks, which were assigned to the 5 d →4 f allowed transitions of Eu 2+ ions and characteristic optical 5 D 4 – 7 F J ( J =6, 5, 4, and 3) transitions of Tb 3+ ions, respectively. The emission color of BSP:Eu 2+ , y Tb 3+ exhibited a controlled luminescence evolution in the green area owing to the Eu 2+ –Tb 3+ energy transfer process. [ABSTRACT FROM AUTHOR]

Up-conversion phosphors BaLa 2 ZnO 5 co-doped with Ho 3+ /Yb 3+ were synthesized by high temperature solid-state reaction method. The phase composition of the phosphors was characterized by X-ray diffraction (XRD). The structure of BaLa 2 ZnO 5 : 0.75% Ho/15% Yb phosphor was refined by the Rietveld method and results showed the decreased unit cell parameters and cell volume after doping Ho 3+ and Yb 3+ , indicating Ho 3+ and Yb 3+ have successfully replaced La 3+ . Under the excitation of 980 nm diode laser, the strong green and weak red up-conversion emissions centered at 548 nm, 664 nm and 758 nm were observed, which originating from 5 S 2 , 5 F 2 → 5 I 8 , 5 F 4 → 5 I 8 and 5 S 2 , 5 F 2 → 5 I 7 transitions of Ho 3+ ions, respectively. The optimum doping concentrations of Ho 3+ and Yb 3+ were determined to be 0.75% and 15%, and the corresponding Commission International de L'Eclairage (CIE) coordinates are calculated to be x =0.298 and y =0.692. The related UC mechanism of Ho 3+ /Yb 3+ co-doped BaLa 2 ZnO 5 depending on pump power was studied in detail. The results indicate that BaLa 2 ZnO 5 : Ho 3+ /Yb 3+ can be an effective candidate for up-conversion yellowish-green light emitter. [ABSTRACT FROM AUTHOR]

Er 3+ and/or Yb 3+ doped Sr 2 ScF 7 up-conversion (UC) phosphors were synthesized, and the optimum doping concentrations of Yb 3+ and Er 3+ in the Sr 2 ScF 7 host were found to be 20% mol and 7% mol, respectively. Under excitation of 980 nm laser, the UC spectra of the samples is composed of three green emission bands from 510 to 570 nm centered at 525, 543 and 551 nm and two red emission band from 640 to 690 nm with two peaks at 657 and 671 nm, which is attributed to the 2 H 11/2 , 4 S 3/2 → 4 I 15/2 and 4 F 9/2 → 4 I 15/2 transitions of Er 3+ , respectively. The UC emission color of Er 3+ can be tuned by adjusting the intensity ratio of red to green emission through manipulating the population of red and green emitting states. [ABSTRACT FROM AUTHOR]

BaLa2ZnO5:Er3+/Yb3+ has been synthesized via a high temperature solid-state method, and the tunable upconversion luminescence and energy transfer process between Yb3+ and Er3+ in this system have been demonstrated. Upon 980 nm laser excitation, the intense green and red emission around 527, 553, and 664 nm were observed for BaLa2ZnO5:Er3+/Yb3+, which can be assigned to the characteristic energy level transitions of 2H11/2 → 4I15/2, 4S3/2 → 4I15/2, and 4F9/2 → 4I15/2 of Er3+, respectively. The critical Er3+ quenching concentration (QC) was determined to be about 5 mol%, and the power studies indicated that mixture of 2- and 3-photon process was responsible for the green and red upconversion luminescence. [ABSTRACT FROM AUTHOR]

Emission-tunable phosphors Ca 9 La(PO 4 ) 5 (SiO 4 )F 2 :Ce 3+ ,Tb 3+ with apatite structure were synthesized by a solid-state reaction. The phase structure, photoluminescence (PL) properties, lifetimes and the PL thermal stability were investigated, respectively. The phosphor exhibited an asymmetric broad-band blue emission (Ce 3+ ) with peak at 403 nm and the line-type green emission with peak at 543 nm (Tb 3+ ). The varied color of the phosphors from blue to green can be achieved by properly tuning the relative ratio of Ce 3+ /Tb 3+ through the energy transfer from Ce 3+ to Tb 3+ ions. The critical distance was calculated to be 8.78 Å by using the concentration quenching method. When the temperature turned up to 150 °C, the emission intensity of Ca 9 La(PO 4 ) 5 (SiO 4 )F 2 :Ce 3+ ,Tb 3+ phosphor was 77% of its initial value at room temperature, which indicated the good thermal stability of the sample. All the properties indicate that the Ca 9 La(PO 4 ) 5 (SiO 4 )F 2 :Ce 3+ ,Tb 3+ phosphor has potential application of color-tunable w -LEDs. [ABSTRACT FROM AUTHOR]

An anti-defect engineering strategy, inspired by photocatalytic and photovoltaic materials, was proposed to develop high-efficiency phosphors in whitlockite families. Significant enhancement of photoluminescence intensity (2.46 times), thermal stability (87.92% at 150 °C), cathodoluminescence intensity (3.34 times), quantum efficiency (IQE sharply up to nearly 100%) were simultaneously realized by constructing a rigid structure and removing vacancy defects. The developed phosphors exhibited promising applications in the fields of warm-white LEDs, plant growth lighting and information security. [Display omitted] • Anti-defect engineering strategy is proposed to develop high-efficiency phosphors. • The internal quantum yield is sharply improved from 38.90% to 99.07%. • The mechanism of improvement is revealed by defect-related characterizations. • DFT calculation shows the positive role of Debye temperature and alkali metal ions. • Promising applications in warm-white LEDs / plant-growth lighting are demonstrated. Lacking an effective strategy to simultaneously address the challenges of quantum efficiency, luminescence intensity and thermal stability has become the key bottleneck for further development and large-scale application of solid-state lighting technology. Herein, inspired by the defect-engineering used in photoelectrocatalytic and photovoltaic materials, we acted in a diametrically opposite way and unprecedentedly proposed an anti-defect engineering strategy to develop high-efficiency phosphors. By constructing a rigid structure and introducing alkali metals M to remove cation vacancy defects, similar to building blocks and jigsaw puzzle, we developed three groups of whitlockite phosphors, namely Ca 3- x Sr x (PO 4) 2 :Ce3+, Ca 3 (PO 4) 2 :Ce3+, M and (Ca 0.5 Sr 0.5) 3 (PO 4) 2 :Ce3+,Na+,Mn2+, and synchronously realized the significant enhancement of photoluminescence intensity (2.46 times), thermal stability (87.92% at 150 °C), cathodoluminescence intensity (3.34 times), quantum yield (from 38.90% to 99.07%). We characterized the defect concentration by positron annihilation technique (PAT), and calculated Debye temperature (ΘD) and simulated the occupation of M according to DFT theory to reveal the improvement mechanism. Some advanced applications were also explored in this work, including warm-white LEDs, plant growth lighting and information security. The anti-defect engineering proposed in this work may contribute to the further development of high-efficiency phosphors for the next-generation smart solid-state lighting technologies. [ABSTRACT FROM AUTHOR]

Highlights: [•] Near-infrared emitting phosphors LaOCl:Nd3+/Yb3+ were prepared. [•] LaOCl:Nd3+/Yb3+ samples show strong near-infrared emission lines in the region of 1060–1150nm and 980–1050nm. [•] The possible energy transfer mechanism between Nd3+ and Yb3+ was discussed. [ABSTRACT FROM AUTHOR]

Novel reddish Mg 3 Gd 2 Ge 3 O 12 : RE3+ (RE = Sm, Eu) phosphors with high thermal stability have been designed and developed. In this work, Mg 3 Gd 2 Ge 3 O 12 was first synthesized for being used as the phosphor host. The X-ray diffraction and Rietveld refinement testified that the MGGO: Sm3+ and MGGO: Eu3+ crystallized in a cubic unit cell with space group I a-3d (230). The photoluminescence properties were studied in detail, MGGO: Sm3+ and MGGO: Eu3+ can be obviously excited at 403 and 395 nm, which could guarantee efficient absorption through commercial n -UV chip. Benefiting from the inverse garnet highly rigid framework, MGGO: 0.04Sm3+ and MGGO: 0.9Eu3+ phosphors had a favorable thermal resistance due to large activation energies (MGGO: 0.04Sm3+: 0.291 eV, MGGO: 0.9Eu3+: 0.238 eV). The emission intensity of MGGO: 0.04Sm3+ and MGGO: 0.9Eu3+ can still preserve about 97.85% and 91.58% at working temperature (423 K) compared to the initial intensity (298 K). All results indicated Mg 3 Gd 2 Ge 3 O 12 : RE3+ (RE = Sm, Eu) phosphors have potential usage for full-spectrum w-LED applications as red component. • Crystal structure of MGGO: 0.04Sm3+ and MGGO: 0.9Eu3+ phosphors are investigated in detail. • MGGO: 0.04Sm3+ and MGGO: 0.9Eu3+ phosphors have a favorable thermal resistance due to large activation energies. • MGGO: 0.04Sm3+ and MGGO: 0.9Eu3+ can be obviously excited at 403 and 395 nm. • CIE chromaticity coordinates of MGGO: 0.04Sm3+ and MGGO: 0.9Eu3+ are (0.5153, 0.4709) and (0.4937, 0.3765). [ABSTRACT FROM AUTHOR]

Hydroxyapatite (HAP) commonly undergoes doping with various dopants, leading to the emergence of new properties. In this study, HAP is co-doped by terbium (Tb) and europium (Eu) to impart HAP with photoluminescent properties. By controlling the Tb3+ amount to 7.5 × 10−5 mol unchanged, it is observed that when the doping amount of Eu3+ reaches 4.0 × 10−5 mol, the band gap measures 3.919 eV, with maximum fluorescence intensity. Notably, a dipole-dipole energy transfer type from Tb3+ to Eu3 was identified during this process. Concentration quenching occurs when the Eu3+ amount exceeds 4.0 × 10−5 mol. In addition, the Tb3+ and Eu3+ co-doped HAP demonstrates excellent thermal stability and a more comprehensive emission wavelength range than Tb3+-doped HAP or Eu3+-doped HAP. Considering these properties, Tb3+ and Eu3+ co-doped HAP phosphor and aramid/polyphenylene sulfide (ACFs/PPS) fiber paper are organically compounded, resulting in functional fabrics with excellent low-temperature stability. These available fabrics are made of luminescent crystals and fibers can be applied in fields such as high-performance textile testing. Notably, when a specific laser irradiates the damaged area of the textile, fluorescence is not detected by the detector. Moreover, Tb3+ and Eu3+ co-doped HAP has also been shown to be used in the light-emitting diode (LED) to produce the HAP-LED that emits warm white light without commercial phosphors. That expands the application of HAP in anti-counterfeiting, flexible wearables, high-performance textile testing, and semiconductor devices. The color-tunable Tb3+ and Eu3+ co-doped HAP is prepared by hydrothermal synthesis co-precipitation. The energy transfer process between Tb3+ and Eu3+ is proved and the application possibility of Tb3+ and Eu3+ co-doped HAP in fluorescence anti-counterfeiting and LED is discovered. [Display omitted] • The energy transfer mechanism of Tb3+ and Eu3+ in HAP was studied. • By controlling the doping amount of Eu3+, the fluorescence color of Tb3+ and Eu3+ co-doped HAP was tunable. • It expands the application of hydroxyapatite in fluorescent anti-counterfeiting and LED. • HAP exhibited excellent stability when combined with fibers for anti-counterfeiting applications. • The LED emitting bright white light was prepared by using Tb3+ and Eu3+ co-doped HAP without commercial phosphor. [ABSTRACT FROM AUTHOR]

What ideal w-LED phosphors always aim to do is to achieve a single phase near-sunlight emission phosphor simultaneously with both high luminescence efficiency and high thermal stability at operation temperature. And It is well known that apatite compound phosphors are one of the most promising optical materials to realize those above because of their unique structure enhanced luminescence properties and thermal stability. Here, we synthesized a co-doped single phase apatite phosphors Ca2La8(SiO4)6O2:Dy3+/Sm3+ (CLSO:Dy3+/Sm3+) for white light emission, which was provided with excellent thermal stability and of which luminescence intensity at 150 °C still was 92 percentage of that at room temperature. Moreover, X-ray diffraction technique, Fourier transform infrared spectroscopy, scanning electron microscope were employed to characterization of phase structure and morphology, and consequently pure apatite structure and gravel-like morphology of phosphors were proved. Analysis of photoluminescence spectra indicated that concentration quenching effect exist in single-doped CLSO:Dy3+ phosphors owing to dipole-dipole interaction between Dy3+ ions. It is revealed that maybe exist Dy3+ ↔ Sm3+ bilateral non-radiative energy transfer processes in Dy3+/Sm3+ co-doped CLSO system by PL spectra and decay curves. And variation of Sm3+ ion concentration can control color emission, namely CIE chromaticity coordinates and correlated color temperature, finally to achieve white light emission (0.309,0.309) with CCT 6848 K, able to be a potential candidate for commercial lighting applications. [ABSTRACT FROM AUTHOR]

Abstract A set of Eu3+, Dy3+ and Tb3+ doped novel scheelite-type LiCaGd(WO 4) 3 (LCGW)-based phosphors was prepared via a conventional solid-state reaction method. The X-ray diffraction (XRD), transmission electron microscopy (TEM) analysis, characteristics of luminescence, PL thermostability, decay lifetimes, as well as CIE coordination were investigated to characterize the as-prepared samples in detail. The XRD analysis indicated that the Eu3+, Dy3+ and Tb3+ ions were incorporated into the LCGW host lattice. Under the ultraviolet radiation, the characteristic emission lines of Eu3+ (5D 0 –7F 2), Dy3+ (4F 9/2 –6H 13/2) and Tb3+ (5D 4 –7F 5) ions were observed. The Eu3+ and Tb3+ single-doped LCGW fluorescent powders showed bright red and green emissions, respectively, without concentration quenching. As well as the Dy3+ doped LCGW phosphors radiate a strong yellow light at optimal Dy3+ concentration 0.08 mol. The efficient energy transfer phenomenon was observed for the Eu3+/Dy3+ and Tb3+/Dy3+ ions. The emission color of the LCGW: x Tb3+/0.08Dy3+ samples was tuned from yellow (0.4074, 0.4727) to green (0.3604, 0.5521) via adjusting the Tb3+ concentration. The emission color of LCGW: y Eu3+/0.08Dy3+ can be tuned from yellow (0.491, 0.3856) to red (0.5694, 0.3512) by variation of the Eu3+/Dy3+ ratio. Additionally, the thermal stability of the luminescence in the LCGW phosphors doped by Eu3+, Tb3+, Dy3+ ions was studied. The results verified that the LCGW:Ln3+ (Ln = Tb, Eu, Dy) phosphors are promising for applications in white LEDs. [ABSTRACT FROM AUTHOR]

Abstract A series of reddish-emitting apatite-type phosphor LiGd 9 (SiO 4) 6 O 2 :Sm3+ was prepared by using an appropriate solid-state method. The photoluminescence (PL), photoluminescence excitation (PLE) spectra, and decay times of the samples were characterized to investigate the photoluminescence properties for application in white light-emitting diodes (w -LEDs). The photoluminescence investigations showed that LiGd 9 (SiO 4) 6 O 2 :Sm3+ phosphor emitted reddish emission, which ascribed to the transitions of the Sm3+ from the 4G 5/2 excited state to the 6H 5/2 , 6H 7/2 , and 6H 9/2 states, respectively. The critical quenching concentration of Sm3+ in LiGd 9 (SiO 4) 6 O 2 phosphors were determined to be about 3 mol%. Moreover, the spectroscopic data and fluorescence decay dynamics indicate that the energy transfer from Gd3+ to Sm3+ ions takes place in LiGd 9 (SiO 4) 6 O 2 : Sm3+ phosphor. All the results indicated that the LiGd 9 (SiO 4) 6 O 2 : Sm3+ phosphor could efficiently assimilate the near ultraviolet (n -UV) light and act as a suitable warm light candidate for n -UV w -LEDs. [ABSTRACT FROM AUTHOR]

A series of novel luminescent emission-tunable phosphors Mg 2 La 8 (SiO 4 ) 6 O 2 :Ce 3+ ,Tb 3+ (MLS:Ce 3+ ,Tb 3+ ) have been prepared by a solid-state reaction. The phase formation was firstly confirmed through X-ray diffraction technique and refined by the Rietveld method. The MLS:Ce 3+ ,Tb 3+ phosphors, which crystallized in apatite-type hexagonal phase, exhibited a broad excitation band ranging from 200 to 400 nm and several emission bands centered at 426 nm and 551 nm. Energy transfer from Ce 3+ to Tb 3+ ions via a dipole-dipole mechanism occurred in the as-synthesized phosphors upon ultraviolet (UV) excitation. The energy transfer efficiency increases with increasing doping content of Tb 3+ ions, which was confirmed by the luminescence spectra and fluorescence decay curves of corresponding ions simultaneously. The energy transfer critical distance was calculated and evaluated by both the concentration quenching and spectral overlap methods. The chromaticity of emission-tunable phosphors was also characterized by the Commission International de l'éclairage (CIE) chromaticity indexes, and the color tone can be tuned from blue (0.179, 0.122) to green (0.267, 0.408) by controlling the ratio of Ce 3+ /Tb 3+ . [ABSTRACT FROM AUTHOR]

A series of solid solution phosphors Ca 9 La(PO 4 ) 5 [(Si 1- x Ge x )O 4 ]F 2 :Ce 3+ with apatite structure in the P 6 3 / m space group have been prepared. The novel solid solution phosphors show continuously controlled violet-blue emission. It is found that both substantial spectra broadening (45 → 100 nm) and red-shift (404 → 422 nm) can be realized with the continuous introduction of [GeO 4 ] 4- into the crystal lattice which has been simulated by a crystal-field model. The above results indicate that the tetrahedral substitution is interesting to induce spectral tuning properties based on the chemical composition control of the iso-structural solid solutions. [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]

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]

A series of novel green emission Whitlockite-type Ca8ZnLa(PO4)7:Eu2+ and color tunable Ca8ZnLa(PO4)7:Eu2+,Mn2+ phosphors were prepared by the solid-state reaction method in a reducing atmosphere. Its crystal structure and phase composition were identified by high-resolution transmission electron microscopy, selected area electronic diffraction, X-ray photoelectron spectroscopy, and X-ray powder diffraction Rietveld refinement, and it was found to be trigonal, belonging to R-3 c(161) space group. The luminescence properties of Eu2+ singly doped and Eu2+/Mn2+ codoped Ca8ZnLa(PO4)7 phosphors were revealed in detail. Ca8ZnLa(PO4)7:Eu2+ is excitable over a broad range from 200 to 450 nm with a prominent green emitting. With varied Eu2+/Mn2+ ratios, fine-tune emission under 365 nm excitation can be achieved from green (0.221, 0.468) to magenta (0.391, 0.276), especially the warm white light (0.392, 0.352), and CCT 3500 K can be obtained by the process of energy transfer between Eu2+ and Mn2+. The ET mechanism in this system is managed via the dipole-dipole interaction with the maximum energy-transfer efficiency 82.8% based on the decay lifetime data. These results suggest that as-prepared phosphors can serve as promising candidates of UV-pumped w- LEDs. [ABSTRACT FROM AUTHOR]

A series of blue-emitting La 5.90− x Ba 4+ x (SiO 4 ) 6− x (PO 4 ) x F 2 :0.10Ce 3+ ( x = 0, 1, 2, and 3) phosphors with apatite structure were synthesized by a solid-state reaction. The crystal structure and the photoluminescence properties were investigated in detail. The crystallographic occupancy of Ce 3+ in La 2.90 Ce 0.10 Ba 7 (SiO 4 ) 3 (PO 4 ) 3 F 2 and La 5.90 Ce 0.10 Ba 4 (SiO 4 ) 6 F 2 were studied based on Rietveld refinements results and the crystal chemistry rules. La 5.90− x Ba 4+ x (SiO 4 ) 6− x (PO 4 ) x F 2 :0.10Ce 3+ exhibited strong blue light emission in the range of 407–414 nm with high thermal stability upon excitation at 276 nm. Besides, the activation energy E of La 5.90 Ce 0.10 Ba 4 (SiO 4 ) 6 F 2 and La 2.90 Ce 0.10 Ba 7 (SiO 4 ) 3 (PO 4 ) 3 F 2 phosphors were calculated to be 0.152 and 0.177 eV. These results suggest that La 5.90− x Ba 4+ x (SiO 4 ) 6− x (PO 4 ) x F 2 :0.10Ce 3+ is a potential blue phosphor candidate for near-UV-pumped w -LEDs. [ABSTRACT FROM AUTHOR]

Single-phase Ba 10− x − y (PO 4 ) 6 O: x Eu 2+ , y Mn 2+ samples with apatite structure have been synthesized via a solid-state reaction method. The phase structure, luminescence properties, lifetime, PL thermal stability, as well as fluorescence decay curves of the samples were investigated. Effective energy transfer occurs from Eu 2+ to Mn 2+ in Ba 10 (PO 4 ) 6 O and a possible mechanism of the energy-transfer from Eu 2+ to Mn 2+ is proposed. The critical distances R c was calculated by concentration quenching and turned out to be about 0.817 nm ( x c =0.21). The CIE and thermally stable luminescence behaviors of Ba 9.94 (PO 4 ) 6 O:0.06Eu 2+ phosphor were also studied in detail. All the results indicate that Ba 10− x − y (PO 4 ) 6 O: x Eu 2+ , y Mn 2+ phosphors have potential applications as near UV-convertible phosphors for white light-emitting diodes. [ABSTRACT FROM AUTHOR]

Currently, the application potential of Cr3+ doped near-infrared (NIR) fluoride phosphors excited by blue light is promising. However, the development of near-infrared fluoride phosphors with wider emission bandwidth remains a challenge. Herein, we employed the hydrothermal method to prepare K 2 NaCrF 6 :Fe3+ phosphors. Upon excitation at 432 nm, the K 2 NaCrF 6 :xFe3+ phosphors exhibited broad near-infrared emission, with the main peak ranging from 752 nm to 780 nm. As the Fe3+ concentration increased, the luminescence intensity of the K 2 NaCrF 6 :xFe3+ phosphor decreased, accompanied by a redshift in the emission band and an increase in the full width of the emission spectrum half-peak. These changes can be attributed to the dipole-dipole interaction, specifically the energy transfer between Fe3+ and Cr3+, leading to the 4T 2 (4F) → 4A 2 (Cr3+) and 4T 1 (4G) → 6A 1 (6S) (Fe3+) transitions. • K 2 NaCrF 6 :Fe3+ phosphors display application potential for near-infrared (NIR) fluorescence when excited by blue light. • The developed phosphors exhibit a broad near-infrared emission bandwidth (752–780 nm) under 432 nm excitation. • Increasing Fe3+ concentration leads to redshift and broadening of the emission spectrum. • Luminescent changes are attributed to dipole-dipole interactions and efficient energy transfer. • Cr3+ and Fe3+ enables synchronous excitation processes, offering versatility for applications in spectroscopy. [ABSTRACT FROM AUTHOR]

A series of novel luminescent phosphors Sr 10 (PO 4 ) 6 O:Eu 2+ with apatite structure were synthesized via a high temperature solid-state reaction. The phase structure, photoluminescence (PL) properties, the PL thermal stability, as well as the fluorescence decay curves of the samples were investigated to characterize the resulting samples, and the selected Sr 9.97 (PO 4 ) 6 O:0.03Eu 2+ phosphor exhibits strong thermal quenching resistance, retaining the luminance of 88.73% at 150 °C. The quenching concentration of Eu 2+ in Sr 10 (PO 4 ) 6 O was about 0.03 attributing to the dipole–quadrupole interaction. The Sr 10 (PO 4 ) 6 O:Eu 2+ phosphor exhibited a broad-band blue emission at 439 nm upon excitation at 346 nm. The results indicate that Sr 10 (PO 4 ) 6 O:Eu 2+ phosphors have potential applications as near UV-convertible phosphors for white-light UV LEDs. [ABSTRACT FROM AUTHOR]

A series of new luminescent emission-tunable phosphors Sr 2 La 8 (SiO 4 ) 6 O 2 :Ce 3+ , Tb 3+ with apatite structure have been synthesized by a high temperature solid-state reaction. The phase structure, photoluminescence emission and excitation spectra, lifetime, as well as the effect of Tb 3+ concentration are investigated to characterize the resulting samples. The critical distance was calculated to be 8.26 Å by using the concentration quenching method. The intense green emission was observed in the Sr 2 La 8 (SiO 4 ) 6 O 2 :Ce 3+ , Tb 3+ phosphors on the basis of the efficient energy transfer from Ce 3+ to Tb 3+ with an efficiency of 68.55%. And a possible mechanism of the energy-transfer from Ce 3+ to Tb 3+ ion is also proposed. The results indicate that Sr 2 La 8 (SiO 4 ) 6 O 2 :Ce 3+ , Tb 3+ phosphors have potential applications to be used as near UV-convertible phosphors for white light-emitting diodes because of the broad excitation in the near-ultraviolet range and the efficient green emission light. [ABSTRACT FROM AUTHOR]

SrIn2O4, which shows lower phonon energy than CaIn2O4, is not only a good photocatalyst but also can be an excellent up-conversion (UC) host to exhibits UC luminescence. In this work, Yb3+ and/or Er3+ doped SrIn2O4 phosphors were synthesized, and their UC luminescence properties were studied and compared with those in the CaIn2O4 host. The structure of SrIn2O4: 0.01Er3+ and SrIn2O4: 0.1Yb3+/0.01Er3+ samples were refined by the Rietveld method and found to that SrIn2O4: 0.1Yb3+/0.01Er3+ showed increasing unit cell parameters and cell volume, indicating In3+ sites were substituted successfully by Yb3+ and/or Er3+ ions. From the UC luminescence spectra and diffuse reflection spectra, Er3+-doped SrIn2O4 showed very weak luminescence due to ground state absorption of Er3+; Yb3+/Er3+ codoped SrIn2O4 presented strong green (550 nm) and red (663 nm) UC emissions which were assigned to energy transfer from Yb3+ transition 2F7/2→2F5/2 to the Er3+ transition 4S3/2 → 4I15/2 and 4F9/2 → 4I15/2. Comparing with CaIn2O4, Yb3+/Er3+ codoped SrIn2O4 showed obvious advantages with higher UC luminescent intensity. The pumping powers study showed that UC emissions in Yb3+/Er3+ codoped SrIn2O4 were attributed to energy transfer of Yb3+→Er3+ with a two-photon process. The possible UC luminescent mechanism of Yb3+/Er3+-doped SrIn2O4 was discussed. [ABSTRACT FROM AUTHOR]

Near-infrared excited up-conversion phosphors of RE 3+ /Yb 3+ (RE = Ho, Tm) co-doped SrIn 2 O 4 were synthesized by a solid-state reaction method. X-ray diffraction analysis revealed the phase composition of those samples, and the up-conversion spectroscopic properties were studied in terms of up-conversion emission spectra. Under 980 nm near-infrared laser excitation, strong green emission with the peak at 546 nm was observed in SrIn 2 O 4 : Ho 3+ /Yb 3+ , which can be assigned to the characteristic 5 S 2 ( 5 F 4 ) → 5 I 8 transition of Ho 3+ . Furthermore, SrIn 2 O 4 : Tm 3+ /Yb 3+ showed bright blue emission with the peak at 486 nm, which is associated with the 1 G 4 → 3 H 6 transition of Tm 3+ . The UC power studies indicated that the luminescence of SrIn 2 O 4 : Ho 3+ /Yb 3+ and SrIn 2 O 4 : Tm 3+ /Yb 3+ are attributed to two-photon and three-photon process, respectively. The possible UC luminescence mechanism and energy transfer in SrIn 2 O 4 : RE 3+ /Yb 3+ were discussed. [ABSTRACT FROM AUTHOR]

Pyroxene‐type phosphors were widely developed due to the advantages of high chemical stability, luminous efficiency, and low production cost. In this contribution, a series of Eu2+/Tb3+ co‐doped Ca0.75Sr0.2Mg1.05Si2O6 (CSMS) phosphors with pyroxene structure were successfully synthesized by the solid‐state method. Under the 340 nm excitation, the emission peaks of the phosphor show a redshift with the increase of Eu2+ concentration. The emitting color of Eu2+/Tb3+ co‐doped samples shows a redshift attributed to the energy transfer from Eu2+ to Tb3+. Simultaneously, acquired thermometer exposes superbly temperature‐sensitive properties (Sa and Sr having maximum values 4.7% K−1 and 0.6% K−1, respectively) over the cryogenic temperature range (77–280 K). Furthermore, it has good stability and precision at cryogenic temperatures, indicating that CSMS:0.03Eu2+/0.03Tb3+ phosphor is a very promising fluorescent material suitable for cryogenic temperature sensing. [ABSTRACT FROM AUTHOR]

The series of novel phosphors Ca 9 La(PO 4) 5 [(Si 1- x Ge x O 4)]F 2 :0.15Dy3+ with x = 0, 0.25, 0.50, 0.75 and 1 (CLPS 1- x G x F:0.15Dy3+) with apatite-type structure (space group P 6 3 / m) has been synthesized. The crystal structure and electronic structure have been studied by powder X-ray diffraction (PXRD) in combination with the atomic-scale density functional theory (DFT) calculations. A combination of Raman, nuclear magnetic resonance (29Si NMR) spectroscopy and the evolution of Dy3+ ions photoluminescent properties was used to characterize the local crystal structure features. Based on the variation of the [SiO 4 ] by [GeO 4 ] tetrahedral substitutions in the apatite-type structure, the difference in the thermal stability and decay curves of CLPS 1- x G x F:0.15Dy3+ phosphors were referred to crystal chemical stability of as-prepared compounds, which is also confirmed by the values of polyhedral distortion, bond valence sum (BVS) and DFT calculations. The present study provides new insights the synthetic methodology and fundamental characterizations into the design of new phosphors combined with theoretical methods. [ABSTRACT FROM AUTHOR]

Ce3+ doped K 3 LuF 6 powders have been successfully elaborated via high-temperature solid state method. The structural and luminescent properties of these cryolite-type K 3 LuF 6 : x Ce3+ (x = 0.03, 0.05, 0.07, 0.10 and 0.13) phosphors have been investigated into detail. The results indicate that all phases belong to the monoclinic system with P2 1 /n space group and lattice parameters a = 6.295 (4) Å, b = 6.497 (5) Å, c = 8.992 (6) Å, β = 90.91 (3) ° for x = 0.05. Ce3+ is considered to substitute for Lu3+ in the octahedral [LuF 6 ] sites. Under UV light excitation at 307 nm, the photoluminescence spectra of the samples present one broad band centered around 432 nm which belongs to the purplish-blue region. The color coordinates of this phase are calculated to (0.1565, 0.0956). The influence of Ce3+ content on the luminescence properties is also established and the concentration quenching mechanism is due to dipole-quadrupole Ce3+-Ce3+ interactions in K 3 LuF 6 :Ce3+. Rietveld refinement of XRD pattern and crystal structure of K 3 LuF 6 :0.05Ce3+ (left); The PL spectra of K 3 LuF 6 :xCe3+ (x = 0.03, 0.05, 0.07, 0.10, and 0.13) monitored by excitation at 307 nm and the inset is dependence of PL intensity on the Ce3+ doping content (right). Image 1 [ABSTRACT FROM AUTHOR]

It is urgent and crucial to develop highly efficient broadband Near-infrared (NIR) phosphor-converted light-emitting diodes (pc-LEDs) which are applied in tiny solid-state NIR light sources. However, a lot of NIR phosphors suffer from low quantum yield and poor thermal stability in recent years. Hereon, the solid-state reaction synthesis process was used to create a new garnet Ca 2 GdZr 2 Ga 3 O 12 :Cr3+ (CGZG:Cr3+) phosphor, which can produce a broad range emission peak at (12,437 cm-1, 804 nm) with a full width at half maximum (FWHM) of (67567 cm−1, 148 nm). At 373 °C, thermal stability was determined to be 76%, an IQE of 75% and an EQE of 26% was observed. When driving current at 150 mA and 320 mA, the device achieved the output power of 473 mW and 968 mW. The results demonstrate CGZG:Cr3+ phosphor-convert NIR LEDs have great potential for applications in night-vision and biomedical imaging NIR spectroscopy technology. • The Ca 2 GdZr 2 Ga 3 O 12 :Cr3+ is found ultra-broadband near-infrared photoluminescence with peak at 804nm.and FWHM 148 nm. • The Ca 2 GdZr 2 Ga 3 O 12 :Cr3+ near-infrared phosphors with the very high outpower 968 mW@320 mA. • The Ca 2 GdZr 2 Ga 3 O 12 :xCr3+ is promising for use in night-vision and biomedical imaging NIR spectroscopy technology. [ABSTRACT FROM AUTHOR]

Phosphor is the decisive material in white light-emitting diodes (WLED), affecting light quality. Silica phosphate has good stability, low cost and environmentally friendly features, so it has great application potential. In this paper, a self-activated reddish-orange phosphor Ca 3 Gd 7 (PO 4)(SiO 4) 5 O 2 : x Sm3+ was prepared by the high-temperature solid-phase method. The phase purity of the sample was verified by X-ray diffraction (XRD). The Rietveld refinement method was used to resolve further the sample structure and the location of the substitution of rare earth ions. The photoluminescence properties were studied in detail using fluorescence spectra, temperature-dependent emission spectra and other characterization methods. The electron transition and energy transfer processes of Gd3+ in Ca 3 Gd 7 (PO 4)(SiO 4) 5 O 2 were analyzed. The fluorescence decay curve of the sample was obtained, which belongs to the double exponential curve, and the decay lifetime depending on the Sm3+ doping concentration was calculated. Furthermore, a WLED device was assembled, and warm white light was obtained, with a spectrum showing characteristic red emission, proving to complement the missing red component of commercial WLEDs. These results indicate that Ca 3 Gd 7 (PO 4)(SiO 4) 5 O 2 : x Sm3+ phosphor has great potential for application. • The reddish-orange-Emitting phosphor Ca 3 Gd 7 (PO 4)(SiO 4) 5 O 2 : x Sm3+ was obtained via the high-temperature solid-state method. • The structure of Ca 3 Gd 7 (PO 4)(SiO 4) 5 O 2 : x Sm3+ phosphor, including the incorporation sites of Sm3+, were investigated. • The mechanism of energy transfer in the luminescence process of samples was studied. • The optical properties of Ca 3 Gd 7 (PO 4)(SiO 4) 5 O 2 : x Sm3+ reddish-orange-emitting phosphor were investigated carefully. [ABSTRACT FROM AUTHOR]

A series of novel Na 3 Ga (1- x ) F 6 : x Eu 3+ ( x  = 1%, 3%, 5%, 7% and 10%) phosphors were synthesized by hydrothermal synthesis method. The crystal structure and luminescence properties of Na 3 GaF 6 :Eu 3+ were characterized by X-ray powder diffraction (XRD), Scanning electron microscope (SEM), photoluminescence (PL) and photoluminescent excitation spectra (PLE) as well as decay curves. The results indicated that Eu 3+ can replace Ga 3+ in the lattice of Na 3 GaF 6 without any impurity. The micro-particle of the phosphor was uniform and regular with a smooth surface. Upon 395 nm excitation, the phosphors show intense reddish-orange color including a series of narrow peaks attributed to the typical f–f transition of Eu 3+ . Not like most of other rare-earth doped sample, the Na 3 GaF 6 :Eu 3+ phosphors show obvious anti-thermal quenching behavior. All the results demonstrated that Na 3 GaF 6 :Eu 3+ phosphors exhibit good luminescent properties and might have a potential to applications in lighting technology. [ABSTRACT FROM AUTHOR]

Abstract A single-component white-emitting phosphor Sr 9 La(PO 4) 5 (SiO 4)F 2 :Dy3+ pumped for n -UV-light emitting diodes was firstly presented by solid state method and the crystal structures, luminescence properties, especially the concentration quenching behaviors were discussed in detail. Accordingly, the quantum efficiencies as well as lifetime studies of Dy3+ in CLPGF phosphor were also carried out. The results revealed that the Sr 9 La(PO 4) 5 (SiO 4)F 2 :Dy3+ phosphor could be efficiently excited in a broad wavelength ranging near ultraviolet (n -UV) regions, which matched perfectly with n -UV white light emitting diodes (w -LEDs) chips. Under the excitation at 349 nm, the phosphor exhibited three prominent emission peaks in the visible wavelength region located at 483, 578 and 670 nm, which is ascribed to the 4F 9/2 -6H 15/2 , 4F 9/2 -6H 13/2 and 4F 9/2 -6H 11/2 transitions of Dy3+, respectively. It was also proved that the dipole-dipole interactions results in the concentration quenching in Sr 9 La(PO 4) 5 (SiO 4)F 2 :Dy3+ phosphors. Fascinatingly, when the temperature turned up to 150 °C, the emission intensity at 483 and 578 nm was 83.4 and 89.1% of the initial value at room temperature. Additional, the corresponding activation energy Δ E was determined to be 0.16999 and 0.17451 eV, which indicated the excellent thermal stability of the samples. All these findings demonstrated that as-prepared phosphors could act as a high-performance candidate for the application. Highlights • A single-component white-emitting phosphor has been successfully prepared. • As-prepared phosphor has good thermal stability and luminescence efficiency. • The structural data of Sr 9 La(PO 4) 5 (SiO 4)F 2 :Dy3+ is firstly reported. [ABSTRACT FROM AUTHOR]

Samarium (III) doped fluorapatite phosphors La 6- x Ba 4 (SiO 4 ) 6 F 2 : x Sm 3+ (LBSF: Sm 3+ ) were synthesized for the first time, via the conventional high-temperature solid-state method in the air atmosphere. The samples were measured by X-ray diffraction, scanning electron microscopy and photoluminescence spectroscopy, i.e. emission and excitation spectra, as well as luminescence decay curves. The as-prepared samples can be excited in the range from 300–500 nm, centered at 404 nm. Photoluminescence measurements showed the emission spectra are composed of four sharp peaks characteristic of Sm 3+ ions, at about 565, 603, 650 and 711 nm. The critical concentration for quenching of Sm 3+ ions in the LBSF matrix is about 0.12 mol. According to the Dexter's theory, the mechanism of energy transfer between Sm 3+ ions was considered to be dipole-quadrupole (d-q) interactions, with the critical distance calculated by the concentration quenching method to 9.89 Å. Moreover, the temperature-dependent emission spectra showed that the as-prepared phosphors have good thermal stability, with an activation energy of about 0.161 eV. Finally, according to the CIE coordination, the phosphor exhibited reddish-orange emission. Thanks to the mentioned favorable structural and optical properties, the Sm 3+ -doped La 6 Ba 4 (SiO 4 ) 6 F 2 phosphors have a potential application character, for the near ultraviolet white light emitting diodes. [ABSTRACT FROM AUTHOR]

Upconversion phosphors Sr 2 LaF 7 co-doped with Yb 3+ and Er 3+ are synthesized via hydrothermal method. The phase compositions of Sr 2 LaF 7 phosphors with different amounts of Yb 3+ and Er 3+ dopants, pH values, and complexing agents are characterized by X-ray diffraction (XRD). The crystal structure and morphology of Sr 2 LaF 7 phosphor doped with 15% Yb 3+ / 1% Er 3+ is refined by the Rietveld method and transmission electron microscopy (TEM). Under 980 nm laser excitation, Yb 3+ and Er 3+ co-doped Sr 2 LaF 7 phosphors exhibit red emission around 670 nm generated by the 4 F 9/2 → 4 I 15/2 transition and green emissions centering around 550 nm and 523 nm generated by the 4 S 3/2 → 4 I 15/2 and 2 H 11/2 → 4 I 15/2 transitions of Er 3+ , respectively. The optimum synthetic conditions for upconversion luminescence for Sr 2 LaF 7 co-doped with Yb 3+ and Er 3+ are discussed and determined to be 15% Yb 3+ / 1% Er 3+ with EDTA-2Na as the complexing agent under pH value = 8, and the corresponding Commission International de L′Eclairage (CIE) coordinates are calculated to be x  = 0.4293 and y  = 0.5589 with reddish yellow color visible to naked eyes under the 980 nm laser excitation. The related upconversion mechanisms of Yb 3+ and Er 3+ co-doped Sr 2 LaF 7 depending on the pump power are also studied in detail. [ABSTRACT FROM AUTHOR]

In this paper, Ce 3+ -activated iso-structural solid solutions La 5.99 Ce 0.01 M 4 (SiO 4 ) 6 F 2 (M = Ca, Sr and Ba) compounds were prepared for the first time. The structure and luminescence properties of the samples were investigated to explore the difference of cation substitution. The phase analysis indicated that all XRD peaks of the samples were indexed by a hexagonal cell with the space group of P 6 3 /m, and the phosphors showed strong blue light emission with broad bands. With the isomorphous substitution of Ba → Sr → Ca, the average bond length between Ce 3+ and anions is decreased and the crystal field around Ce 3+ is strengthened, resulting in the red-shift (from 410 nm to 423 nm) of the emission wavelength for La 5.99 Ce 0.01 M 4 (SiO 4 ) 6 F 2 (M = Ca, Sr, Ba). [ABSTRACT FROM AUTHOR]

Er 3+ / Yb 3+ doped BaIn 2 O 4 up-conversion (UC) phosphors are synthesized and their UC luminescent properties are characterized. BaIn 2 O 4 has P 21 /c space group but Rietveld refinement suggests it has twice smaller cell parameter (a = 10.3975 Å, b = 5.8295 Å, c = 14.4457 Å) and volume than previous reported structure. Refinement also reveals Er 3+ /Yb 3+ replaces In 3+ ions in lattice because of the existence of InO 6 octahedra. In these BaIn 2 O 4 phosphors, co-doping with Yb 3+ ions changes the predominant UC emission from green ( 2 H 11/2 , 4 S 3/2 → 4 I 15/2 of Er 3+ ) to red (about 665 nm, 4 F 9/2 → 4 I 15/2 of Er 3+ ). By controlling of Er 3+ /Yb 3+ concentrations, the BaIn 2 O 4 phosphors have the potential of generating various UC spectra and color tunability. The pumping powers study shows two-photon process in these phosphors. [ABSTRACT FROM AUTHOR]

LED occupies a broad market due to its many advantages as a fourth-generation solid-state light source. However, single-component white LED generally has the disadvantages of high coloring temperature, low thermal stability, and low luminous efficiency. In order to solve these problems, Gd 5 Si 2 BO 13 :Dy3+,Eu3+ was prepared by a high temperature solid state method using a newer borate matrix based on Gd 5 Si 2 BO 13. A colour-tunable warm white phosphor was achieved by energy transfer between Dy3+ and Eu3+. The crystal structure, luminescence characteristics, thermal stability of luminescence, fluorescence lifetime and energy transfer mechanism were systematically studied, and the samples obtained had excellent luminescence performance. Its thermal stability of 150 °C luminescence was 83.77%. By adjusting the ratio of Eu3+, its color changes from cool white light to warm white light and finally moves to red light. Its corresponding color temperature can be adjusted to a range of 5475k∼2128 K. The packaging w-LED application test and the application test of colorless fluorescent anti-counterfeiting printing ink were carried out, and both showed excellent performance. This is the first time that Dy3+ and Eu3+ have been studied in Gd 5 Si 2 BO 13 , further understanding the newer substrate Gd 5 Si 2 BO 13 , and promoting the application of single-component warm white LED. Therefore, Gd 5 Si 2 BO 13 :Dy3+,Eu3+ have good market application prospects. [Display omitted] • Through the energy transfer between Dy3+ and Eu3+, Gd 5 Si 2 BO 13 :Dy3+/Eu3+ shows excellent Warm white light performance. • The phosphor showed good luminescence thermal stability, UV stability and wet resistance stability. • The color temperature of the sample was adjusted from 5475K to 2128K by adjusting the doping concentration of Eu3+. • The LED application test with Gd 5 Si 2 BO 13 :Dy3+,Eu3+ package shows good performance. [ABSTRACT FROM AUTHOR]

Single-phase KLaSr3( PO4)3F: Sm3+ phosphors with fluorapatite structure were prepared via high-temperature solid-state method in air atmosphere for the first time. The X-ray diffraction, scanning electron microscope, diffuse reflectance spectra, photoluminescence spectra, and temperature-dependent emission spectra, as well as lifetimes were measured to characterize the as-prepared phosphors. Phase results indicated that KLaSr3( PO4)3F: Sm3+ belongs to hexagonal system with a space group of P-6. Photoluminescence measurements showed the emission spectrum was composed of four sharp peaks at about 564, 602 (the strongest one), 646, and 702 nm, corresponding to the 4G5/2-6 H J ( J=5/2, 7/2, 9/2, and 11/2) transitions of Sm3+ ions. The optimum doping concentration of Sm3+ ions was turned out to be 0.03 (mol), and the mechanism of energy transfer among Sm3+ ions was considered to be dipole-dipole interaction by using Dexter's theory. In addition, the critical distance Rc for energy transfer among Sm3+ ions were calculated to be 9.97 Å according to Blasse concentration quenching method. The selected KLa0.97Sr( PO4)3F: 0.03Sm3+ exhibited high thermal stability with an activation energy of 0.163 eV. Besides, the Commission International de l'Eclairage chromaticity coordinate of the phosphor were located in the orange-reddish light region. [ABSTRACT FROM AUTHOR]

Developing color-tunable phosphors via the introduction of co-doping activators and sensitizers to the host with energy transfer processes has been a state-of-the-art topic for a long time. In this work, novel emission-tunable oxyapatites-type Ba 10 (PO 4 ) 6 O:Eu 2+ ,Tb 3+ /Li + phosphors were prepared via a high temperature solid state reaction for the applications in white light emitting diodes ( w -LEDs) with higher color rendering index. Tunable colors from blue to green can be realized in the Ba 10 (PO 4 ) 6 O:Eu 2+ ,Tb 3+ /Li + by varying the relative ratios of Eu 2+ to Tb 3+ , showing good absorption in the range of 230–400 nm. The energy transfer mechanism from Eu 2+ to Tb 3+ ions was demonstrated to be a quadrupole-quadrupole interaction by combining the Inokuti-Hirayama (I H) model and Reisfeld's approximation. Importantly, a prototype white lamp was packaged by mixing Ba 9.83 (PO 4 ) 6 O: 0.03Eu 2+ , 0.07Tb 3+ , 0.07Li + and commercial red phosphor CaAlSiN 3 : Eu 2+ , and the lamp exhibits a higher color rendering index (Ra = 92 and R9 = 56) and warm correlated color temperature of 4361 K for the actual application. Better luminescent properties compared to commercial Y 3 A l5 O 12 :Ce 3+ -based w -LEDs, indicating that Ba 10 (PO 4 ) 6 O: Eu 2+ , Tb 3+ /Li + phosphors are emerging as potential phosphor-converted w -LEDs. [ABSTRACT FROM AUTHOR]