Effect of synthesis conditions on Ce3 + luminescence in borate glasses

Abstract

Cerium exhibits two stable valence states, i.e. Ce3+ and Ce4+. In glassy hosts, Ce4+ strongly deactivates the Ce3+ luminescence and therefore it becomes essential to employ reducing conditions in the glass synthesis. In the present work, we report a systematic study on the effect of different synthesis conditions on Ce3+ luminescence properties in borate glasses. In the air atmosphere synthesized glasses, strong Ce4+ charge transfer (CT) transitions have been observed, which led to poor luminescence properties with quantum yield less than 1%. The Ce3+ luminescence significantly improved in glasses prepared under reducing synthesis atmosphere suggesting effective reduction of Ce4+ ions to the Ce3+ state. In both mild to strong reducing conditions, the decay profiles were single exponential with decay lifetime of about 46ns. Among the studied synthesis conditions, the glass prepared under strong reducing condition using carbon enclosed double crucible plus 0.5wt.% carbon doping showed best performance with luminescence quantum yield of about 42%, which is one of the highest value in the glassy hosts reported so far.