β-Na(Y1.5Na0.5)F6:Tm3+-A blue upconversion phosphor

A luminescent material beta-Na(Y1.5Na0.5)F-6 doped with Tm3+ was synthesized by a solid-state reaction method for a steady phosphor of blue upconversion. Under the 671 nm laser excitation, the green emission band of 511 nm due to the D-1(2) -> H-3(5) transition is obtained for the first time, while the ultraviolet emission band is also observed at 368 nm, associated with the D-1(2) -> H-3(6) transition. Especially, a wide band of blue emissions is obtained at the wavelength region of 440-490 nm, originated mainly from the D-1(2) -> F-3(4) (450 nm) and (1)G(4) -> H-3(6) (471-487 nm) transitions, which have potential application in tunable solid-state blue laser of Tm3+. The upconversion mechanism is explored in terms of the energy-level structures of Tm3+ ion and the power dependence of upconverted emission intensity, which is believed to be performed by excited-state absorption. (C) 2008 Elsevier B.V. All rights reserved.