Luminescence behavior of Er3+ ions in glass–ceramics containing CaF2 nanocrystals

The upconversion luminescence and near infrared luminescence of the Er3+ ions in transparent oxyfluoride glass–ceramics containing CaF2 nanocrystals have been investigated. The formation of CaF2 nanocrystals in the glass–ceramics was confirmed by XRD. The oscillator strengths for several transitions of the Er3+ ions in the glass and glass–ceramics have been obtained and then the Judd–Ofelt parameters were calculated. The split near infrared emission peaks of the Er3+ ions in the glass–ceramics can be observed because the Er3+ ions have been incorporated into crystalline environment of the CaF2 nanocrystals. The upconversion luminescence intensity of Er3+ ions in the glass–ceramics increased significantly with increasing heat treated time. The transition mechanism of the upconversion luminescence has been ascribed to a two-photon absorption process.