Erbium upconversion luminescence in transparent glass ceramics containing ternary fluoride nanocrystals

Upconversion luminescence is an anti-Stokes process in which photons with low energy are converted to ones with higher energy. The efficiency of this process is determined by the properties of activator and host matrix. In this research Er3+ upconversion luminescence is analysed in oxyfluoride glass ceramics – composites consisting of oxide glass and fluoride nanocrystals.

Novel transparent glass ceramics containing NaREF4 (RE=La, Gd, Y, Er, Lu) and Ba4RE3F17 (RE=Gd, Y, Yb, Lu) has been prepared using melt quenching method. The crystallization and spectroscopic properties have been analysed in glass and glass ceramics.

Main theses:

  • In the glass ceramics containing NaLaF4: Er3+, Yb3+ increase of Yb3+ content promotes the formation of cubic fluorite type NaLaF4, which currently has been obtained only in oxyfluoride glass ceramics.
  • In the crystalline environment of β-NaREF4: Er3+ containing glass ceramics two Er3+ positions are associated with incorporation of erbium ions in the rare earth ion positions and the third is related to distortion of these sites caused by half-filled cationic positions.
  • In Ba4RE3F17: Er3+ containing glass ceramics variations in the local environment of Er3+ ions are associated with the phase transition from metastable cubic to rhombohedrally-distorted cubic Ba4RE3F17.
  • In Ba4Yb3F17: Er3+ containing glass ceramics unusually intense red upconversion luminescence is attributed to three photon energy transfer from Yb3+ to Er3+, followed by multiphonon relaxation and cross-relaxation between Er3+ and Yb3+.
  • In Ba4Lu3F17: Er3+ containing glass ceramics the Er3+ content in the crystalline phase can be determined by comparing luminescence band intensity ratio and luminescence kinetics of Er3+ in glass ceramics and microcrystalline Ba4Lu3F17: Er3+ with known activator content.