Upconversion luminescence in Er-doped germanate-oxyfluoride and tellurium-germanate-oxyfluoride transparent glass-ceramics

Upconversion luminescence has been studied for Er in a germanate-oxyfluoride and a tellurium-germanate-oxyfluoride transparent glass-ceramic using 800 nm excitation. Significantly increased upconversion luminescence was observed from transparent glass-ceramics compared with that from their corresponding as-prepared glasses. In addition to a strong green emission centered at 545 nm from S3/2 state and a weaker red emission centered at 662 nm from F9/2 state generally seen from Er -doped glasses, a violet emission centered at 410 nm from H9/2 state and a near-ultra-violet emission centered at 379 nm from G11/2 state were also observed from transparent glassceramics. The upconversion luminescence of Er ions in transparent glass-ceramics revealed sharp Stark-splitting peaks generally seen in a crystal host. The increased upconversion efficiency is attributed to the decreased effective phonon energy and the increased energy transfer between excited ions when Er ions were incorporated into the precipitated b-PbF2 nanocrystals. r 2006 Elsevier B.V. All rights reserved. PACS: 78.55.Hx; 78.55Qr; 78.67Bf