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Red phosphor is indispensable to achieve warm white light in the white light diode (WLED) application. However, the current red phosphors suffer from high cost and harsh synthesis conditions. In this study, an oxide‐based rare‐earth‐free red‐emitting phosphor Li3Mg2NbO6:Mn4+ (LMN:Mn4+) has been successfully synthesized by a simple solid‐state reaction method. The relationship between crystal structure and luminescence was investigated in detail. The site occupancy of the doping Mn4+ ion in the LMN host has been discussed from the point of bond valence sum. How the coordination environment of doping Mn4+ affects the energy level of doping Mn4+ ion has been illustrated via the Tanabe‐Sugano energy‐level diagram. Moreover, warm white light has been obtained using LMN:Mn4+ as compensator to the YAG:Ce3+. [ABSTRACT FROM AUTHOR]

White light-emitting diodes (WLEDs) have been considered as the next generation lighting technology due to their advantages such as high efficiency and environmental friendliness. However, current mainstream WLEDs, which are based on blue chips and the Y3Al5O12:Ce3+ yellow phosphor, suffer from the problem of low color rendering index (CRI). To solve this problem, a yellowish-green phosphor Ca1.5Y1.5Al3.5Si1.5O12:Ce3+ (CYAS:Ce3+) based on the garnet structure has been designed in this study. Its crystal structure, band structure, and luminescence properties have been investigated in detail. CYAS:Ce3+ exhibits efficient and thermal-stable yellowish-green emission. The 5d centroid shift and crystal splitting of the Ce3+ ion in CYAS have been analyzed together with the structure. Moreover, good warm white light with a low correlated color temperature (3210 K), high color rendering index (85.1) and luminous efficacy (88.5 lm W−1) has been obtained by combining CYAS:Ce3+ and the red phosphor CaAlSiN3:Eu2+ with a blue LED chip. [ABSTRACT FROM AUTHOR]

A novel apatite‐based UV‐excited dual‐emitting Ca2Na2La6(SiO4)4(PO4)2O: Eu2+/Eu3+ phosphor (CNL: Eu2+/Eu3+) was designed and successfully synthesized by a solid‐state reaction. Compared with previous reports on this family of materials, a structural study based on DFT calculation exhibited a new consequence that the monovalent ions in this system are more inclined to occupy the seven‐coordinate cationic sites rather than the nine‐coordinate sites. This result was confirmed by the structural refinement and high‐resolution transmission electron microscopy (HRTEM) data. Due to the coexistence of Eu2+ and Eu3+ dopants in the material, under 345 or 392 nm excitation, CNL: 0.02Eu2+/Eu3+ exhibited a green Eu2+ emission band (528 nm) and red Eu3+ emission peaks (around 618 nm). The application potential of CNL:0.02Eu2+/Eu3+ in luminescent thermometry was studied by exploiting the temperature sensitivity of the fluorescent intensity ratio (green/red) at different temperatures. It was found that, under 345 nm excitation, the fluorescent intensity ratio of CNL: 0.02Eu2+/Eu3+ displayed linear correlation over the temperature range of 298 to 473 K with a high sensitivity of 2.82%K−1. Additionally, the emission color of the CNL: 0.02Eu2+/Eu3+ sample under UV lamp (254 and 365 nm) excitation showed an obvious change (from green to red) as the temperature increased from 298 to 473 K (from green to red). These results indicated that CNL: Eu2+/Eu3+ can serve as an excellent visual luminescent ratiometric thermometer. Furthermore, this work provides a novel reference for developing high‐performance luminescence temperature‐sensing materials. [ABSTRACT FROM AUTHOR]

Highlights • A new orange phosphor GGAON 0.5 :Ce3+ with sufficient red component was synthesized. • No decay in the 10 microsecond is the key feature applied in AC-circuit directly. • Self-packed LED lamp emits warm white light with high rendering index. Abstract Solid solution phosphors Gd 3 Ga 2 (Al 3- y Si y)(O 12- y N y):Ce3+ were synthesized by introducing [Si4++N3–]/[Al3++O2–] co-substitution into the lattice of Gd 3 Ga 2 Al 3 O 12 :Ce3+. Gd 3 Ga 2 Al 3 O 12 :Ce3+, characteristic as outstanding light yield (about 50–60 kPh/ MeV), and has been applied in computer tomography (CT), positron emission tomography (PET) nuclear medical detector, et al. With the increase of y value, the coordination environment around Gd3+(Ce3+) shrinked, which were confirmed by combining techniques of structure refinement, energy- dispersive spectrum, elements distribution mapping. As a result, stronger 5 d orbital nephelauxetic effect (ε c) and bigger 5 d energy level splitting (ε cfs) were induced. Thus resulting in longer wavelength of excitation and emission from Ce3+, and broadening of emission spectra. The typical sample Gd 2.95 Ga 2 Al 2.5 Si 0.5 O 11.5 N 0.5 :0.05Ce3+ (GGASON 0.5 :Ce3+) exhibits sufficient red component and persistent luminescence(>10 ms), enables fabrication of warm white light suited for alternating-current (AC) when combined with blue light chip (460 nm). [ABSTRACT FROM AUTHOR]

The rare-earth free tunable full-color-emitting Si-BCNO phosphors were synthesized at low temperature (below 800 °C) for 45 min by solid state reaction method using urea, boric acid, polyethylene glycol and silica as raw materials. The prepared samples exhibited single, distinct and broad photoluminescence emission bands varied from blue (470 nm) to red (620 nm) upon excitation at 370 nm by varying the concentrations of Si and sintering temperatures. The decay curves signified that the luminescence was induced by two luminescence centers, related to longer lifetime τ 1 and shorter lifetime τ 2 . The temperature-dependent PL intensity of the phosphor has been also investigated, which performs good thermal stability. It is believed that the Si-BCNO phosphor could be a possible material for multicolor light-emitting diodes. [ABSTRACT FROM AUTHOR]

A series of SrSiAl2O3N2:Eu2+ (0.005 ≤x≤ 0.05) phosphors were successfully synthesized through a pressureless, facile, and efficient solid state route. The crystal structure, band structure, and their photoluminescence and cathodoluminescence properties were investigated in detail. The phosphors exhibit rod shape morphology with a uniform Eu2+ distribution. Under n-UV excitation the emission spectra shift from 477 to 497 nm with an increase of Eu2+ concentration. The concentration quenching mechanism of Eu2+ emission was dominated by the dipole–dipole interaction. The thermal stability is comparable to that of the commercial Ba2SiO4:Eu2+ phosphor. The phosphor also exhibits high current saturation and high resistance under low voltage electron bombardment. All the results indicate that the SrSiAl2O3N2:Eu2+ phosphors can be considered as candidates for application in both white LEDs and FEDs. [ABSTRACT FROM AUTHOR]

The promising green oxynitride phosphor, Ba3−xMgxSi6O12N2:Eu2+ was synthesized by the solid-state reaction method. The effect of Mg2+ doping on the structure and photoluminescence (PL) properties of Ba3Si6O12N2:Eu2+ was investigated systematically. The results reveal that the phosphor retains the single phase of Ba3Si6O12N2, with the lattice expanding upon increasing the Mg2+ concentration, in an appropriate range. This suggests that a large portion of Mg2+ enters into the interstitial sites of the crystal lattice. At a certain concentration, Mg2+ doping can greatly enhance the absorption and PL intensity and decrease the full widths at half maximum (FWHM) of Ba3Si6O12N2:Eu2+ phosphors. The green phosphor Ba2.87Eu0.1Mg0.03Si6O12N2 exhibited a small thermal quenching, which remained 82% of the initial emission intensity when measured at 150 °C. The quantum efficiency measured at 400 nm excitation was 38.5%. All the results indicate that the solid solution Ba3−xMgxSi6O12N2:Eu2+ can be a good candidate for phosphors applicable in n-UV LEDs for solid-state lighting. [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]

Abstract: Bi3+ doped Ca12Al14O32Cl2 series were successfully synthesized by conventional solid-state reaction method and their luminescence properties have been investigated in detail. Crystallographic parameters of the refinement structure with cubic space group I-43d were obtained by XRD refinement as a =12.0183(3)Å and V (cell volume)=1735.93(1)Å3. The resulting phosphors absorb ultraviolet (UV) light (240–400nm) and show a single intense broad emission band in the wavelength range of 400–600nm with maximum intensity at 483nm. The Commission Internationale de 1’Eclairage (CIE) chromaticity coordinates are about x =0.185, y =0.306. Thus, the novel light blue-emitting phosphor Ca12Al14O32Cl2:Bi3+ could be potentially applied in UV white light-emitting diodes. [Copyright &y& Elsevier]

Abstract: Rare-earth-doped β-SiAlON phosphors, with the compositions of Si6− z Al z O z N8− z :xRe (z =1, Re=Sm or Dy, 0.01⩽ x ⩽0.05), were prepared by a solid-state reaction at high temperature. The photoluminescence properties were investigated as functions of the rare earths (i.e., x) concentration. In β-SiAlON:Sm2+, broad 4f 55d 1 →4f 6 emission and line 5 D 0 → 7 FJ emission were observed at room temperature. The characteristic 4 F 9/2 →6 H 15/2 (blue) and 4 F 9/2 →6 H 13/2 (yellow) transitions of Dy3+ were detected in the emission spectra. And the thermal quenching properties of β-SiAlON:Sm2+ and β-SiAlON:Dy3+ were investigated. [Copyright &y& Elsevier]

Abstract: β-SiAlON:Ln3+ (Ln=Yb/Ho, Yb/Er) microparticles with up-conversion (UC) luminescence properties were successfully synthesized via a solid-state reaction method by employing Si3N4 (nanopowder), Al2O3 (nanopowder) and rear-earth oxides. The results show that the β-SiAlON:Ln3+ microparticles have a size ranging from 100 to 400nm. Under the 980nm NIR laser excitation, Yb/Er and Yb/Ho codoped samples exhibit UC luminescence centered at 658 and 660nm, respectively. The power dependency and the dynamics of the UC luminescence confirm the existence of two-photon UC processes in Yb/Er and Yb/Ho codoped samples respectively, and the UC mechanisms were given. [Copyright &y& Elsevier]

Abstract: A novel ZrO2:Sm3+,Sn4+ phosphor is synthesized by solid state reaction. The ZrO2:Sm3+ does not show afterglow. But, after doping Sn4+, intense red afterglow luminescence is firstly observed in ZrO2:Sm3+,Sn4+ and it can last more than 1000s at maximum. The afterglow decay curves of ZrO2:Sm3+,Sn4+ are fitted by three exponential components and the decay process consists of initial fast, intermediate and slow decay. The thermoluminescence indicates that the Sn4+ ions induce suitable traps with the depth of 0.436eV and result in efficient afterglow luminescence of ZrO2:Sm3+,Sn4+. The thermoluminescence filling and fading experiments further confirm the important role of the proper shallow traps induced by doping Sn4+ on the afterglow of ZrO2:Sm3+,Sn4+. [Copyright &y& Elsevier]

Novel Ca 1.96 (B 1- y Si y)(O 3- y N y)Cl:0.04Eu2+ phosphors were designed and synthesized by introducing [Si4++N3−]/[B3++O2−] co-substitutions into Ca 2 BO 3 Cl:Eu2+ lattice. Fourier Transform Infrared Spectroscopy (FTIR) show that typical planar [BO 3 ]3− units gradually transformed into [BO 4 ]5− units with the increase of y , which was firstly realized in luminescence materials. Uneven expansion of cell parameters a,b, and c were confirmed by the combination of X-ray diffraction spectra (XRD) and results of Rietveld refinement. Structure variation caused smaller centroid shift (ε c) and 5 d energy level splitting (ε cfs), inducing the narrowing of excitation spectra (y = 0 → y = 0.2, 168 → 144 nm) and blue-shift of emission spectra (y = 0 → y = 0.2, 582 → 525 nm). Excellent thermal stability (6% loss at 150 °C) was obtained, which resulted from more covalent bonding. Using the combination of representative sample CBSOCN 0.2 : 0.04Eu2+ and red K 2 SiF 6 :Mn4+ in a blue LED driven lamp, white light with high CRI ~92.8 and color temperature closed to the summer sun (5770 K) was obtained. Unlabelled Image • [Si4++N3−]/[B3++O2−] co-substitution was applied to synthesize the Ca 2 (B 1- y Si y)(O 3- y N y)Cl:Eu2+ series. • Luminescence color change from yellow to green with the increase of y. • Thermal stability of samples increased with the increase of y. • White light with high CRI can be synthesized by using the optimal sample CBSOCN 0.2 : 0.04Eu2+. [ABSTRACT FROM AUTHOR]

Abstract: Yellow-orange oxynitride Ca-α-SiAlON: Eu2+ phosphors with the compositions of Ca0.8Si9.2Al2.8O1.2N14.8: xEu2+ (x =0–0.24) were obtained via carbothermal reduction and nitridation method. Crystallographic parameters of the refinement structure with triclinic space group P31c (159) were obtained by XRD refinement as a = b =7.8859(3)Å, c =5.7336(2)Å, V =308.7915(3)Å3, Z =1. The resulting phosphors can absorb light in the range of 300–500nm efficiently and show a single intense broad emission band in the wavelength range of 500–700nm with maximum intensity at 580–601nm. The chromaticity coordinates of the synthesized Ca-α-SiAlON: Eu2+ phosphors can be tailored by simply controlling the activator concentration. All the results show that Ca-α-SiAlON: Eu2+ phosphors can be a candidate for warm white LEDs. [Copyright &y& Elsevier]