The effects of GeO2 adulterant on the luminescence properties of Tb-doped silicate glasses

The GeO2-doped, Tb4O7-doped, and GeO2 and Tb4O7 co-doped silicate glasses were synthesized by high-temperature melting method, and their optical spectra were analyzed. The effects of GeO2 adulterant on the luminescence properties of Tb-doped silicate glasses were studied with ultraviolet–visible transmission, excitation and emission spectra. The results showed that the ratio of the absorption induced by Tb3+ ions to that induced by Tb4+ ions in Tb4O7-doped silicate glasses was increased by GeO2 co-dopant. This implies that the Tb3+ ions tend to exist in GeO2 and Tb4O7 co-doped silicate glasses. It was found that the Ge2+ centers could exist in the co-doped silicate glasses, and moreover, there was energy transfer from T1 level of Ge2+ centers to 5D3 level of Tb3+ ions under UV excitation. The way of the transfer was nonradiative energy resonance transfer, and its efficiency increased with increasing the concentration of GeO2.