title: Strong green emission from alpha-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.
authors.affiliation: Advanced Materials Laboratory, National Institute for Materials Science (NIMS), Namiki 1-1, Tsukuba, Ibaraki 305-0044, Japan. Xie.Rong-Jun@nims.gp.jp
authors.forename: R-J
authors.initials: RJ
authors.lastname: Xie
authors.forename: N
authors.initials: N
authors.lastname: Hirosaki
authors.forename: M
authors.initials: M
authors.lastname: Mitomo
authors.forename: K
authors.initials: K
authors.lastname: Uheda
authors.forename: T
authors.initials: T
authors.lastname: Suehiro
authors.forename: X
authors.initials: X
authors.lastname: Xu
authors.forename: Y
authors.initials: Y
authors.lastname: Yamamoto
authors.forename: T
authors.initials: T
authors.lastname: Sekiguchi