Tb3+ luminescence as a tool to study clustering of lanthanide ions in oxynitride glasses

The 5D3 and 5D4 emission of Tb3+ under UV-excitation in the 4f7 5d band has been measured as a function of the Tb content in Y–Si–Al–O–N glasses. A strong increase of the 5D4 emission over the 5D3 emission was observed at high Tb3+ contents. This increase can be attributed to cross-relaxation between two neighbouring Tb3+ ions. The feeding ratio of the 5D3 and 5D4 levels (∼0.11) and the interaction distance for cross-relaxation (∼1.43 nm) excludes the presence of Tb3+ clusters, pairs or other abnormalities (like phase separation) in the Tb3+ activated materials.