Tb3+-impregnated, non-porous silica glass possessing intense green luminescence under UV and VUV excitation

A colorless transparent luminescence material was successfully prepared by impregnation of leached, porous glass with Tb3+ ions followed by reductive sintering in a CO atmosphere. Tb3+ emissions under ultraviolet (UV) and vacuum ultraviolet (VUV) excitation clearly showed the most intense emission band to be situated at 543 nm, which corresponds to the 5D4 → 7F5 transition. Sintering of the Tb glass in a reducing atmosphere resulted in a significant enhancement of Tb3+ emission intensity in comparison with sintering in air. The presence of traces of cerium ions was verified in Tb glasses, and more Ce3+ ions were produced as a result of the reductive sintering. The increase in Ce3+ ions was believed to be mainly responsible for the enhancement of 5D3 → 7Fj and 5D4 → 7Fj transitions from Tb3+ ions owing to an energy transfer channel. A clearly defined difference in the spectral energy distribution of Tb3+ emissions was found for 231 nm UV and 160 nm VUV excitation of the Tb glass. The phenomenon of cross relaxation was only observed under 231 nm UV excitation. Different excitation mechanisms were taken into account. Direct excitation of Tb3+ ions together with Ce3+ ions occurred in the Tb glass under the 231 nm UV light, whereas indirect excitation consisting of host absorption of energy and transfer from host to Tb3+ ions occurred under the 160 nm VUV light.