Luminescence Properties of Eu²⁺-Activated Alkaline-Earth Silicon-Oxynitride MSi₂O_2-δN_2+2/3δ (M = Ca, Sr, Ba):  A Promising Class of Novel LED Conversion Phosphors

Abstract

The luminescence properties of Eu 2+ -activated alkaline-earth silicon-oxynitrides have been studied. In the BaO-SiO 2 -Si 3 N 4 system, a new BaSi 2 O 2 N 2 compound was obtained having the monoclinic structure with lattice parameters a ) 14.070(4) Å, b ) 7.276(2) Å, c ) 13.181(3) Å, β ) 107.74(6)°. All MSi 2 O 2-δ N 2+2/3δ :Eu 2+ (M ) Ca, Sr, Ba) materials can be efficiently excited in the UV to visible region (370-460 nm), making them attractive as conversion phosphors for LED applications. A blue-green emission at 490-500 is observed for BaSi 2 O 2 N 2 :Eu 2+ , yellow emission at 560 nm for CaSi 2 O 2-δ N 2+2/3δ : Eu 2+ (δ ≈ 0), and a green-yellow emission peaking from 530 to 570 nm for SrSi 2 O 2-δ N 2+2/3δ :Eu 2+ (δ ≈ 1), the position depending on the exact value of δ. BaSi 2 O 2 N 2 :Eu 2+ is the most promising conversion phosphor for white-light LEDs due to its high conversion efficiency for blue light from InGaN-based LEDs related to its very small Stokes shift.

Luminescence properties of SrSi2O2N2 doped with divalent rare earth ions

“…The emission spectrum shows a single emission band peaking at 539 nm. The position and width of the emission band differs from that reported for a SrSi 2 O 2Àd N 2+2/3d :Eu (d$1) compound with a similar XRD pattern [12], and is comparable with the emission spectrum of a phase that was described as the high-temperature modification of SrSi 2 O 2 N 2 :Eu [11]. The emission band is assigned to the 4f 6 5d 1 -4f 7 (fd) transition on Eu 2+ .…”

“…The SrSi 2 O 2 N 2 host lattice we are about to report was developed in a synthesis approach that earlier led to efficient nitridosilicate phosphors M 2 Si 5 N 8 :Eu 2+ (M ¼ Sr, Ba) [4][5][6]. The strong interest in this class of novel materials is reflected by a number of publications in the last few years on the system Ln-Si-O-N (Ln ¼ La, Gd, Y) in general [7] and the title compound in detail [8][9][10][11][12]. This paper describes the synthesis and continuative studies on the optical properties of luminescent materials based on the SrSi 2 O 2 N 2 host lattice doped with divalent rare earth ions, viz.…”

KCa4(BO3)3:Ln3+ (Ln = Dy, Eu, Tb) phosphors for near UV excited white–light–emitting diodes

“…However, this system lacks thermal stability at higher temperatures above 150 o C. Also, the resultant white light exhibits low color rendering index (R a ) due to lack of individual blue, red and green region colors. [7][8][9] Uniform white-light with high R a can be alternatively achieved by mixing several single color 2+ ) are some of the well-known blue and green phosphors broadly used for the generation of white-light because of their high emission efficiency at vacuum UV excitation (VUV) and prominent R a . 12,13 However, despite many advantages, the final phosphor product suffers from complexities associated with the combination of several phosphors used in the fabrication and its significant degradation during heating, which reduce the lifetime and efficiency of WLEDs.…”

“…12,13 However, despite many advantages, the final phosphor product suffers from complexities associated with the combination of several phosphors used in the fabrication and its significant degradation during heating, which reduce the lifetime and efficiency of WLEDs. 10,11,14 The pursuit in this direction has led to identify new class of phosphors having broadband near white emitting properties based on oxides, [15][16][17][18] oxyfluorides, 19,20 nitrides, 21,22 oxynitrides, [23][24][25] sulfides 26,27 and halides. 28,29 Among all, the oxyfluoride (for example: Sr 2.975-x -Ba x Ce 0.025 AlO 4 F) phosphors have been seen with alacrity as the most efficient matrix for photoluminescence due to their low phonon energy.…”

Fabrication of Eu-doped SrSi₂O₂N₂ phosphor by a solid-state reaction using a new source of Si₂N₂O powder

“…Strontium oxynitride (SrSi 2 O 2 N 2 ) is a triclinic system, 7) and it is composed of (Si 2 O 2 N 2 ) n 2n¹ polyanion and SrO layers. 4) The crystallographic structure of the (Si 2 O 2 N 2 ) n 2n¹ polyanion layers is considered to be very similar to that of Si 2 N 2 O.…”