Tb-doped 12CaO·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.