title: Characterization and optical transition in tb-doped 12CaO x 7Al2O3 powders.
abstract: Tb-doped 12CaO x 7Al2O3 (C12A7:Tb3+) powders with strong green emission were prepared using the sol-gel method. X-ray diffraction, micro-Raman spectra, scanning electron microscopy and absorption spectra showed that C12A7:Tb3+ powders with grain size of 200-300 nm were synthesized. Porous powders could be formed as the concentration of Tb3+ was 5 at%. The absorption band around 209 nm was attributed to the host lattice absorption, and the bands around 255 nm and 274 nm were related to the 4f-5d transitions of Tb3+. The absorption intensity of the visible region was enhanced due to the presence of one 100 nm-diameter hole in every grain of C12A7:Tb3+ powders. The emission spectra showed noticeable influence of Tb-Tb cross relaxation, which favored the green photoluminescence (PL) over the blue PL. The study on the concentration quenching indicated that the energy transfers depopulating the 5D3 and 5D4 levels were assigned to the mechanisms of electric dipole-dipole and exchange interaction, respectively.
authors.affiliation: Center for Advanced Opto-electronic Functional Materials Research, Northeast Normal University, Changchun 130024, People's Republic of China.
authors.forename: L L
authors.initials: LL
authors.lastname: Xue
authors.forename: Y X
authors.initials: YX
authors.lastname: Liu
authors.forename: C S
authors.initials: CS
authors.lastname: Xu
authors.forename: Y C
authors.initials: YC
authors.lastname: Liu
authors.forename: C J
authors.initials: CJ
authors.lastname: Zhao
authors.forename: X T
authors.initials: XT
authors.lastname: Zhang