Luminescence of Tb3+‐ and Ce3+‐Activated Rare Earth Silicates

The luminescence properties of Ce 3+ ‐ and Tb 3+ ‐activated and of Tb 3+ ‐activated are reported. It is shown that activated with Tb 3+ is an excellent phosphor both under UV and x‐ray excitation. In both types of compounds there are two different Ln 3+ sites available for the activator ions, Ce 3+ and Tb 3+ . The results show that the activator ions are incorporated on both sites. The differences in the luminescence properties due to the two types of activator sites are ascribed to the presence of oxygen ions which are coordinated to Ln 3+ ions only and do not belong to any silicate group. The excitation spectra of the Tb 3+ emission of these compounds show excitation bands due to spin‐forbidden and spin‐allowed Tb 3+ 4f‐5d transitions. The positions of these bands can be predicted using the data of the Ce 3+ ‐activated samples.