Strong Green Emission from α-SiAlON Activated by Divalent Ytterbium under Blue Light Irradiation

Abstract

This contribution reports on luminescence properties of divalent ytterbium in alpha-SiAlON at room temperature. Ytterbium-doped alpha-SiAlON powders, with the compositions of (M(1-2x/v)Yb(x))(m/v)Si(12-m-n)Al(m+n)O(n)N(16-n) (M = Ca, Li, Mg, and Y, v is the valency of M, 0.002 < or = x < or = 0.10, 0.5 < or = m = 2n < or = 3.5), were synthesized by sintering at 1700 degrees C for 2 h under 0.5 MPa N2. A single, intense, broad emission band, centered at 549 nm, is observed due to the electronic transitions from the excited state 4f(13)5d to the ground state 4f14 of Yb2+. The luminescence of Yb2+ in alpha-SiAlON occurs at relatively low energy, which is attributable to the large crystal field splitting and nephelauxetic effect due to the nitrogen-rich coordination of Yb2+. The dependence of luminescence properties on the Yb2+ concentration, chemical composition, and annealing is discussed. It is suggested that this novel green phosphor could be applied in white light-emitting diodes (LEDs) when combined with a red phosphor and a blue LED.

Photoluminescence properties of β-SiAlON:Yb2+, a novel green-emitting phosphor for white light-emitting diodes

“…Since it is not necessary for β-SiAlON to accommodate the metal ions for charge compensation, rare-earth ions have been confirmed to locate in the continuous channel by electron microscopy [16] or Pr 3+ ), which provide more options for the use in white LEDs [7,11], [17][18][19]. Doping these rare-earth ions into β-SiAlON host lattice also can obtain optimal PL properties.…”

“…Similar to Eu 2+ , Yb 2+ commonly exhibits 4f-5d fluorescence. Xie et al [17] reported strong green emission in Yb 2+ -doped α-SiAlON arising from the 4f 14 -4f 13 5d interconfigurational transitions of Yb 2+ . In contrast to Yb 2+ -doped fluorides, sulfates and phosphates [22][23][24], this longer-wavelength emission is contributed by the nitrogen-rich location of Yb 2+ that leads to the combination of strong crystal-field splitting of the 5d states of Yb 2+ and high covalent bonding (nephelauxetic effect) between Yb 2+ and (O, N).…”

A novel phosphor for glareless white light-emitting diodes

“…There have been many reports describing the development of phosphors [7][8][9][10][11][12][13][14][15][16] for violet chips, which have an external quantum efficiency that is intrinsically higher than that of blue chips [17][18][19] . A pc-LED with a violet chip generates white light only from the luminescence of the phosphors.…”

Inorganic Phosphor Materials for Lighting

“…Another example is given by the green emitting material aSiAlON doped with Yb 2? [138]. In this case, the doping ion shows luminescence spectra due to 4f 14 $ 4f 13 5d 1 interconfigurational transitions [139].…”

“…The excitation spectrum was monitored at k em = 549 nm and the emission spectrum was recorded at k ex = 342, 300, and 445 nm. Both figures are adapted from [138] Top Curr Chem (Z) (2016) (with doping in the region of 2 %) has been considered by Do et al [143]. Samples were prepared by NaBr-aided solid state reaction in flowing H 2 S. Excitation at 455 nm yields a broad symmetric emission band in the range 500-625 nm, whose maximum is red shifted from 535 to 555 with increasing x (moving from SrGa 2 S 4 to CaGa 2 S 4 ).…”