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Mn4+-activated perovskite-structured ANaWO2F4 (A = Li, Na, K) red phosphors were successfully prepared by a facile co-precipitation method. By changing the A-site ions, the tolerance factor (t) of host material ANaWO2F4 became adjustable. Red emissions in LiNaWO2F4:Mn4+, Na2WO2F4:Mn4+ and KNaWO2F4:Mn4+ were found to be gradually increased. The relationship between the structure and their photoluminescence properties was discussed. The results suggested that a t-dependent photoluminescence behavior may exist in perovskite-structured phosphors. As the tolerance factor increases, the emission intensity of ANaWO2F4 (A = Li, Na, K) red phosphors increases. This work also provides a reference for the exploration and optimization of Mn4+-activated perovskite-structured red phosphors. [ABSTRACT FROM AUTHOR]

In this work, a novel red-emitting oxyfluoride phosphor Na2NbOF5:Mn4+ with an ultra-intense zero-phonon line (ZPL) was successfully synthesized by hydrothermal method. The phase composition and luminescent properties of Na2NbOF5:Mn4+ were studied in detail. The photoluminescence excitation spectrum contains two intense excitation bands centered at 369 and 470 nm, which match well with commercial UV and blue light-emitting diode (LED) chips. When excited by 470 nm blue light, Na2NbOF5:Mn4+ exhibits red light emission dominated by ZPL. Notably, the color purity of the Na2NbOF5:Mn4+ red phosphor can reach 99.9%. Meanwhile, the Na2NbOF5:Mn4+ phosphor has a shorter fluorescence decay time than commercial K2SiF6:Mn4+, which is conducive to fast switching of images in display applications. Profiting from the intense ZPL, white light-emitting diode (WLED) with high color rendering index of Ra = 86.2 and low correlated color temperature of Tc = 3133 K is realized using yellow YAG:Ce3+ and red Na2NbOF5:Mn4+ phosphor. The WLED fabricated using CsPbBr3 quantum dots (QDs) and red Na2NbOF5:Mn4+ phosphor shows a wide color gamut of 127.56% NTSC (National Television Standard Committee). The results show that red-emitting Na2NbOF5:Mn4+ phosphor has potential application prospects in WLED lighting and display backlight. [ABSTRACT FROM AUTHOR]

In this paper, a novel violet excited reddish-orange emitting Sr 3 Ga 2 Sn 1 · 5 Si 2 · 5 O 14 :Sm3+ (SGSSO:Sm3+) phosphor with high thermal stability was designed and synthesized by the high temperature solid state reaction method for the first time. The photoluminescence (PL) properties of the SGSSO:Sm3+ phosphors were investigated systematically. Under 402 nm violet light excitation, SGSSO:Sm3+ phosphor shows reddish-orange emission at 598 nm that is attributed to the 4G 5/2 → 6H 7/2 transition of the Sm3+ ions. Importantly, the PL intensity of SGSSO:Sm3+ at 423 K can maintain 87% of the initial value at room temperature. The high thermal stability of Sm3+ in SGSSO was speculated to be attributed to the energy transfer mechanism of trap formed by the hetero-valent substitution of Sm3+ at Sr2+ sites. Finally, a WLED has been fabricated by combing the violet LED chip with the as-prepared reddish-orange emitting phosphor, commercial blue BaMgAl 10 O 17 :Eu2+ (BAM:Eu2+) and green (Ba,Sr) 2 SiO 4 :Eu2+ ((Ba,Sr)S:Eu2+) phosphors. The results indicated that the as-prepared SGSSO:Sm3+ phosphor can be a potential candidate of the reddish-orange component for violet chip pumped white-light-emitting-diodes. • A novel Sr 3 Ga 2 Sn 1 · 5 Si 2 · 5 O 14 :Sm3+ reddish-orange phosphor was synthesized for the first time. • Sr 3 Ga 2 Sn 1 · 5 Si 2 · 5 O 14 :Sm3+ phosphor can be excited by 402 nm violet light and exhibited a dominant reddish-orange emission. • Sr 3 Ga 2 Sn 1 · 5 Si 2 · 5 O 14 :Sm3+ phosphor demonstrated a high thermal stability. [ABSTRACT FROM AUTHOR]

Abstract: A series of red-emitting Eu3+-doped K2LaNb5O15 niobate phosphors with tetragonal tungsten bronze-type structure were synthesized by the solid state reaction method. The structure of new tungsten bronze-type K2EuNb5O15 was identified by Rietveld refinements to crystallize in the tetragonal space group P4bm, which is isostructural to K2LaNb5O15. The relative intensity of the emission from both 5D0→7F2 and 5D0→7F1 increases with increasing Eu3+ ion concentration. The quenching mechanism of the K2La1−x Nb5O15:xEu system was investigated in detail. The relationship between Photoluminescence properties and the TTB-type structure was discussed. The quantum efficiency of K2EuNb5O15 excited under near-UV light (399nm) is 132% of that of commercial Y2O3:Eu3+ (394nm). The results demonstrated K2EuNb5O15 phosphor as a potential candidate for white light emitting diode pumped by near-UV or blue chip. [Copyright &y& Elsevier]

Site preferences of Eu2+ ions on the Ba2+ sites and the Ca2+ sites were discovered in the mixed cation borosilicate Ba 2 CaB 2 Si 4 O 14 (BCBSO). Eu2+ ions are more likely to locate on the Ba2+ sites over the Ca2+ sites according to the Density Functional Theory (DFT) calculation and the photoluminescence spectrum analysis. The emission band centered at 408 ​nm was confirmed to be generated from the Eu2+ ions located on the Ba2+ sites, while the emission band centered at 548 ​nm was considered to be generated from the Eu2+ ions on the Ca2+ sites. Dual sites occupation results in a collective emission band covering 380 ​nm–780 ​nm in BCBSO:Eu phosphors. By further doping with Sr2+ ions, crystal environment of the luminescence centers could be well modulated, resulting in the tunable emission from yellow to white under UV excitation. The photoluminescence quantum yield was significantly improved from 17.9% to 36.8%. Finally, a series of white LEDs with tunable CCT (from 5132 ​K to 3402 ​K) and high Ra (reach up to 89.6) were obtained using the Ba 2(1- y /3) Ca (1- y /3) Sr y B 2 Si 4 O 14 :0.03Eu single-phase white light emission phosphors. A single-phase white light emission Ba 2(1- y /3) Ca (1- y /3) Sr y B 2 Si 4 O 14 :Eu2+ phosphor with superior advantage in color tunability was designed via tendentious multiple sites occupation strategy. [Display omitted] • Synthesis of Ba 2(1- y /3) Ca (1- y /3) Sr y B 2 Si 4 O 14 :Eu2+ phosphors. • Sites preference of Eu2+ on the sites of Ba2+ and Ca2+. • Cationic substitution to modulate the surrounding lattice environment of Eu2+. • Generation of warm white light by single-phase phosphors. [ABSTRACT FROM AUTHOR]