Locating lanthanide impurity levels in the forbidden band of host crystals

The systematics of f --> d transition energies of divalent lanthanides and charge transfer energies of trivalent lanthanides with type of lanthanide ion and type of host crystal are combined into a three parameter model which predicts the absolute location of the energy levels of divalent lanthanides relative to the valence and conduction band states. Including information on the f --> d transition in Ce(3+) together with some assumptions or further experimental data, the levels of trivalent lanthanides can also be deduced. CaF(2) and YPO(4) are used as examples to demonstrate the model. (C) 2004 Elsevier B.V. All rights reserved.