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Light‐emitting diodes (LEDs) producing pure, highly saturated colors are the industry standard for efficient backlighting of high‐color gamut displays. Vivid color reproduction, matching the eye's perception of nature, is the central paradigm in the design of narrow‐band emitting phosphors. To cover a wide range of naturally occurring color tones, expansion of the color gamut in the green spectral region, and therefore an advanced applicable green phosphor, is highly desired. Herein, the oxonitridoberyllosilicate Ba[BeSiON2]:Eu2+ showing outstanding narrow‐band green emission (λmax ≈526 nm with FWHM ≈1600 cm−1 (≈45 nm), x = 0.212, y = 0.715) when excited with InGaN‐based blue LEDs is presented. High quantum efficiency and low thermal quenching (>90% rel. quantum efficiency at 100 °C) as well as excellent scalability make the material suitable for industrial application in high color‐gamut LED displays. A prototype phosphor‐converted‐LED (pc‐LED), with green‐emitting Ba[BeSiON2]:Eu2+ and K2SiF6:Mn4+ as red phosphor shows an extraordinary coverage in the CIE 1931 color space of 109% compared to the DCI‐P3 standard, topping the widely applied β‐SiAlON:Eu2+ phosphor (104%), making it suitable for use in phone displays, monitors, and television screens. [ABSTRACT FROM AUTHOR]

Abstract: Highly efficient phosphor‐converted light‐emitting diodes (pc‐LEDs) are popular in lighting and high‐tech electronics applications. The main goals of present LED research are increasing light quality, preserving color point stability and reducing energy consumption. For those purposes excellent phosphors in all spectral regions are required. Here, we report on ultra‐narrow band blue emitting oxoberyllates AELi2[Be4O6]:Eu2+ (AE=Sr,Ba) exhibiting a rigid covalent network isotypic to the nitridoalumosilicate BaLi2[(Al2Si2)N6]:Eu2+. The oxoberyllates’ extremely small Stokes shift and unprecedented ultra‐narrow band blue emission with fwhm ≈25 nm (≈1200 cm−1) at λem=454–456 nm result from its rigid, highly condensed tetrahedra network. AELi2[Be4O6]:Eu2+ allows for using short‐wavelength blue LEDs (λem<440 nm) for efficient excitation of the ultra‐narrow band blue phosphor, for application in violet pumped white RGB phosphor LEDs with improved color point stability, excellent color rendering, and high energy efficiency. [ABSTRACT FROM AUTHOR]

In the search for materials for high‐efficiency lighting applications, the color‐point tuning of phosphors for inorganic phosphor converted LEDs (pcLEDs) is of special interest. We expand the recently explored phosphor class of SiBeONs (oxonitridoberyllosilicates) by the synthesis and characterization of SrBe1−xSi2+xO3−2xN2+2x:Eu2+. High temperature synthesis, starting from Sr2N, BeO, SiO2 and Si3N4, yields the target phase as the main product. Upon doping with Eu2+, the pale blue crystals exhibit blue luminescence with emission at 456 nm and a full width at half maximum (fwhm) of 66 nm/3108 cm−1. The structure is an ordered variant of the LaSi3N5 structure type and was elucidated by single‐crystal X‐ray diffraction data. The network in SrBe1−xSi2+xO3−2xN2+2x:Eu2+ is highly condensed with a condensation degree of κ=0.6 comprising corner‐sharing [MX4] (M=Be, Si; X=O, N) tetrahedra, with mixed occupancies on both the ligand and central metal sites. [ABSTRACT FROM AUTHOR]

The nitridosilicate La3-xCa1.5xSi6N11:Eu2+ (x ≈ 0.77) was synthesized in a radiofrequency furnace starting from LaF3, La(NH2)3, CaH2, Si(NH)2, and EuF3. The crystal structure was solved and refined from single-crystal X-ray data in the tetragonal space group P4bm (no. 100) with a = 10.1142(6), c = 4.8988(3) Å, and Z = 2. Thereby, the so far unknown charge balance mechanism in the system (La,Ca)3Si6N11, which is necessary as bivalent Ca2+ substitutes trivalent La3+, was clarified. Accordingly, charge balance is achieved by incorporation of Ca2+ on three cation sites, including an additional third site compared to the homeotypic La3Si6N11 structure type. The results are supported by Rietveld refinement on powder X-ray diffraction data as well as energy-dispersive X-ray spectroscopy. Fourier transform infrared spectroscopy indicates absence of N-H bonds. An optical band gap of ≈ 4.0 eV was determined using UV/vis reflectance spectroscopy. The Eu2+ doped compound exhibits a remarkably narrow emission in the yellow-orange spectral range (λem≈ 587 nm, fwhm ≈ 60 nm/1700 cm-1). Because of the intriguing yellow-orange luminescence, La3-xCa1.5xSi6N11:Eu2+ (x ≈ 0.77) is a promising candidate for application in next-generation amber phosphor-converted light emitting diodes. [ABSTRACT FROM AUTHOR]

Oxo- and (oxo)nitridoberyllates show exceptional potential as host lattices for application in illumination grade phosphor converted (pc)LEDs due to their remarkable electronic and structural characteristics, allowing highly efficient narrow-band emission upon doping with Eu2+. Sr[Be6ON4]:Eu2+, the first example of an oxonitridoberyllate phosphor, exhibits narrow-band cyan emission (λem = 495 nm; full width at half-maximum, fwhm = 35 nm; ≈1400 cm-1), comparable to the emission of the oxonitridosilicate BaSi2O2N2:Eu2+ (fwhm = 35 nm) or a cyan-emitting primary LED (fwhm = 27 nm). Sr[Be6ON4]:Eu2+ reveals a highly condensed rigid 3D network with a remarkably large degree of condensation [i.e., atomic ratio Be:(O,N)] of κ = 1.2 that is achieved by interconnection of highly condensed layers of BeN4 tetrahedra by Be2ON6 units via common edges. The crystal structure of Sr[Be6ON4]:Eu2+ was solved on the basis of single-crystal and powder XRD data (C2/c, no. 15, a = 13.9283(14), b = 5.7582(6), c = 4.9908(5) Å, β = 90.195(1)°, Z = 4, R1 = 0.033, wR2 = 0.065, GoF = 1.046). Sr[Be6ON4]:Eu2+ shows a close structural relationship to other nitride as well as oxide compounds, and therefore closes a structural gap helping to understand relations in Be-containing solid-state materials. The electronic structure of Sr[Be6ON4]:Eu2+ was characterized by X-ray spectroscopy measurements, supported by density functional theory (DFT) calculations. Due to its excellent emission properties, large band gap, rigid 3D network, as well as chemical and thermal stability, Sr[Be6ON4]:Eu2+ is a promising phosphor to close the cyan gap in efficient high-CRI pcLEDs (CRI, color rendering index). [ABSTRACT FROM AUTHOR]

The oxonitridosilicate oxides Y4Ba2[Si9ON16]O:Eu2+ and Lu4Ba2[Si9ON16]O:Eu2+ have been synthesized starting from REF3, RE2O3 (RE = Y, Lu), BaH2, Si(NH)2, and EuF3 in a radiofrequency furnace at 1550 °C. The crystal structures were solved and refined from single-crystal X-ray data supported with Rietveld refinement on X-ray powder diffraction data. Both compounds are isotypic and crystallize in monoclinic space group P21/c (no. 14) with Z = 4 and a = 6.0756(2), b = 27.0606(9), c = 9.9471(3) Å, and β = 91.0008(8)° for RE = Y and a = 6.0290(3), b = 26.7385(12), c = 9.8503(5) Å, and β = 90.7270(30)° for RE = Lu. The unique crystal structure exhibits a three-dimensional network made up from Q4-type SiN4 and Q3-type SiON3 tetrahedra. Containing 4-fold bridging N[4] atoms in star-shaped units [N[4](SiN3)4] next to N[3], N[2], O[1], and noncondensed oxide ions, the title compounds illustrate the vast structural variety in (oxo)nitridosilicates. Under excitation with UV to blue light, Y4Ba2[Si9ON16]O:Eu2+ shows emission in the orange-red spectral range (λmax = 622 nm, full width at half-maximum (fwhm) ≈ 2875 cm-1). Yellow-orange emitting Lu4Ba2[Si9ON16]O:Eu2+ (λmax = 586 nm, fwhm ≈ 2530 cm-1) exhibits high internal quantum efficiency (IQE) ≈ 85%. This makes Lu4Ba2[Si9ON16]O:Eu2+ a promising phosphor for low color rendering index (CRI) warm white phosphor converted light emitting diodes (pcLEDs). [ABSTRACT FROM AUTHOR]

The nitridomagnesosilicates Li2Ca2[Mg2Si2N6]:Eu2+ and Li2(Ca1.88Sr0.12)[Mg2Si2N6]:Eu2+ show narrow-band red emission at 638 and 634 nm, respectively, with an emission bandwidth of 62 nm (∼1513 cm-1) after excitation in the blue spectral region. Ce3+-doped samples show luminescence in the green spectral range (λem = 540 nm). The compounds were synthesized via solid-state metathesis reaction in Li melts. Refinement of single-crystal X-ray diffraction data revealed that Li2(Ca1.88Sr0.12)[Mg2Si2N6] crystallizes isomorphic to Li2Ca2[Mg2Si2N6]: C2/m [Z = 2, a = 5.5744(2), b = 9.8439(3), c = 6.0170(2) Å, β = 97.2520(10)°, R1 = 0.021, wR2 = 0.047]. Crystal composition was checked by EDS and ICP-OES measurements and luminescence properties are compared to state of the art narrow-band red emitting luminophors. On the basis of its narrow-band emission, application of the novel red luminophor in high CRI white pcLEDs is promising. [ABSTRACT FROM AUTHOR]

SrSi2O2N2:Eu2+is anoutstanding yellow emitting phosphor material with practical relevancefor application in high power phosphor-converted light-emitting diodes.The triclinic compound exhibits high thermal and chemical stabilityand quantum efficiency above 90% and can be excited by GaN-based UVto blue LEDs efficiently. We have now discovered a hitherto unknownmonoclinic polymorph of SrSi2O2N2, synthesized by solid-state reaction, which is characterized byan alternating stacking sequence of silicate layers made up of condensedSiON3tetrahedra and metal-ion layers. As proven by single-crystalX-ray diffraction, the arrangement of the silicate layers is significantlydifferent from the triclinic polymorph. The translation period alongthe stacking direction is doubled in the monoclinic modification (P21, Z= 8, a= 7.1036(14), b= 14.078(3), c= 7.2833(15) Å, β = 95.23(3)°, V= 725.3(3) Å3). TEM investigations in combinationwith HRTEM-image simulations confirm the structure model. The powderX-ray diffraction pattern shows that the volume fractions of the monoclinicand triclinic modifications are approximately equal in the correspondingpowder sample. The emission wavelength of 532 nm (fwhm ∼2600cm–1) as determined by single-crystal luminescencemeasurements of the monoclinic phase exhibits a shift to smaller wavelengthsby ∼5 nm compared to the triclinic polymorph. Differences ofthe luminescence properties between the monoclinic and triclinic phaseare interpreted with respect to the differing coordination of Eu2+in both phases. The new monoclinic SrSi2O2N2:Eu2+polymorph is a very attractivephosphor material for the enhancement of color rendition of white-lightpc-LEDs. [ABSTRACT FROM AUTHOR]

Abstract: Sr0.5Ba0.5Si2O2N2:Eu2+ is a promising new phosphor for white light phosphor converted (pc)—LEDs. The material shows broad-band emission due to parity allowed 4f6(7F)5d → 4f7(8S7/2) transition in the yellow spectral range (λ em ≈ 560 nm) while excited with UV to blue radiation. The X-ray powder diffraction pattern shows noticeable intensity maxima indicative for diffuse scattering from planar defects and also “missing” reflections compared to SrSi2O2N2:Eu2+. Rietveld refinement reveals an average structure of Sr0.5Ba0.5Si2O2N2:Eu2+ which is isotypic to that of SrSi2O2N2:Eu2+, with the latter representing a twinned layered oxonitridosilicate with disordered metal atoms. The average structure of Sr0.5Ba0.5Si2O2N2:Eu2+ was refined in space group P1 (no. 1) resulting in lattice parameters a = 7.2059(2), b = 7.3887(3), c = 7.3340(2) Å, α = 88.524(4), β = 84.454(3), γ = 75.980(4)° and V = 377.07(2) Å3. Based on the crystallographic results and considering lattice relaxation behavior as a consequence of lattice expansion, the observed unexpectedly large Stokes shift (as compared to SrSi2O2N2:Eu2+; 3573 vs. 3285 cm−1) can be explained using a least square fit of the emission spectra. With almost identical chromaticity coordinates with respect to the most frequently used commercial LED phosphor YAG:Ce3+ but significantly higher luminous efficacy (LE = 495 lm/W), Sr0.5Ba0.5Si2O2N2:Eu2+ is a promising material for outdoor lighting, e.g. in cool-white pc-LEDs. To elucidate the real structure, powder XRD simulations have been recorded compiling a disorder model taking into account all permutations of metal ion sets and silicate layer orientations. Experimental diffraction data were well reproduced including the diffuse intensities observed in powder XRD and also in SAED patterns. These simulations show that crystallites of Sr0.5Ba0.5Si2O2N2:Eu2+ are built up of small anti-phase domains within larger twin domains. [Copyright &y& Elsevier]

Ba[Mg3SiN4]:Eux (x = 0.005-0.025) is prepared by a solid state metathesis reaction of BaF2, Mg3N2, Si(NH)2, LiN3 as N source, Li as flux, and EuF3 as dopant (Ta tube in evacuated silica tube, 1050 °C, 24 h; cooling to 500 °C within 250 h). [ABSTRACT FROM AUTHOR]