抄録
Synthesis conditions of melilite-type rare-earth silicon oxynitrides (RE2Si3O3N4; RE= La, Ce, Nd, Sm, Gd, Dy, Er and Yb) were examined using Si3N4 and rare-earth oxides as starting materials. The stoichiometric compounds could be synthesized by the solid-state reaction of equimolar RE2O3 (RE=Nd, Sm, Gd, Dy and Er) with Si3N4 at 1700°C for 2 h in N2 atmosphere. When near-ultraviolet light was irradiated to these compounds, only Gd2Si3O3N4 emitted yellow light without activator. The excitation and emission behaviors of Gd2Si3O3N4 were further examined by doping the activator (RE’3+; RE'= Ce, Sm, Tb, Dy and Er). Orange-colored light was emitted by doping S3+ to Gd2Si3O3N4; the relative emission intensity of Gd1.98Sm0.02Si3O3N4 achieved 1.8 (reference: Ca WO4). When Tb3+ was doped to Gd2Si3O3N4, the emission band of Gd2-2xTb2xSi30O3N4 was centered at 545 nm where the green-colored light was emitted; the maximum emission intensity achieved 3.5 (refernce:CaWO4) at x=0.06.
