Electronic structure and optical properties of the lanthanide activated RE3(Al1−xGax)5O12 (RE=Gd, Y, Lu) garnet compounds

The spectroscopy of the lanthanide dopants in the RE3(Al1−xGax)5O12 (RE=Gd, Y, Lu and x=0, 0.2, 0.4, 0.6, 0.8, 1) family of garnet compounds is reviewed providing information on the redshift, the centroid shift, the charge transfer energies, and the host exciton creation energies. Clear and systematic trends with changing composition are identified which enables the prediction of properties on compounds where information is not yet available or incomplete. The data are used as input to the recently developed chemical shift model which then generates the vacuum referred binding energy of electrons in 4f-states and 5d-states of all trivalent and all divalent lanthanides as dopants in the garnet family. The obtained binding energies are in excellent agreement with observed properties like thermal quenching and efficiency of 5d–4f emission, electron trapping in trivalent lanthanides, photoconductivity and thermoluminescence. ► Lanthanide 4f–5d and charge transfer energies in garnet compounds are reviewed. ► Lanthanide level locations in RE3(Al1−xGax)5O12 compounds (RE=Gd, Y, Lu) are presented. ► Absolute electron binding energies in lanthanide impurity and host band states are presented. ► Clear trends with changing size of RE and Ga fraction x are identified and discussed.