title: Eu2+-Doped Sr2B2-2xSi2+3xAl2-xN8+x: A Boron-Containing Orange-Emitting Nitridosilicate with Interesting Composition-Dependent Photoluminescence Properties.
abstract: Novel Sr2-yEuyB2-2xSi2+3xAl2-xN8+xphosphors were investigated as a function of the boron and aluminum over silicon ratio and as a function of the Eu2+concentration. Samples were prepared via solid-state reaction synthesis by carefully controlling the synthesis conditions and composition. At high boron and aluminum content, that is, x = 0, a Eu2+5d-4f emission is observed of which the maximum shifts from 595 nm for low Eu concentrations (y = 0.005) toward 623 nm for high Eu concentrations (y = 0.5). The samples can be excited by UV or blue light up to ∼475 nm. Substitution of [B2Al]9+units by [Si3N]9+units, increasing x up to 0.15, greatly improves the luminescence efficiency up to 46% and shows a very large redshift of the excitation bands with ∼100 nm, while the emission band shifts with ∼10 nm. The shifts are attributed to the lowering of the 5d level as a result of the decreased Eu-N distance upon substitution. Temperature-dependent measurements show that the Eu2+5d-4f emission is largely thermally quenched at room temperature for x = 0 due to thermal ionization toward the conduction band, explaining the low luminescence efficiency. The lowering of the 5d level at larger values of x reduces the thermal ionization and consequently increases the thermal stability and quantum efficiency, resulting in strongly luminescent blue-to-orange conversion phosphors that are interesting for light-emitting diode applications.
authors: Sialon Group, National Institute for Materials Science , Namiki 1-1, Tsukuba, Ibaraki 305-0044, Japan.
authors: Otmar M
authors: OM
authors: Ten Kate
authors: Sialon Group, National Institute for Materials Science , Namiki 1-1, Tsukuba, Ibaraki 305-0044, Japan.
authors: Rong-Jun
authors: RJ
authors: Xie
authors: Sialon Group, National Institute for Materials Science , Namiki 1-1, Tsukuba, Ibaraki 305-0044, Japan.|Graduate School of Chemical Sciences and Engineering, Hokkaido University , Sapporo, Hokkaido 060-6828, Japan.
authors: Chun-Yun
authors: CY
authors: Wang
authors: Sialon Group, National Institute for Materials Science , Namiki 1-1, Tsukuba, Ibaraki 305-0044, Japan.
authors: Shiro
authors: S
authors: Funahashi
authors: Sialon Group, National Institute for Materials Science , Namiki 1-1, Tsukuba, Ibaraki 305-0044, Japan.
authors: Naoto
authors: N
authors: Hirosaki