Systematic and material independent variation of electrical, optical, and chemical properties of Ln materials over the Ln series (Ln = La, Ce, Pr,..., Lu)

A universal model for lanthanide (Ln) materials is presented that describes a systematic and material independent variation of the electronic structure over the Ln series (La, Ce, Pr,..., Lu). The model is derived from experimental data on 4f and 5d energies of Ln ions as impurities in luminescent materials but, as will be shown, can fruitfully be applied to stoichiometric Ln materials as well. The validity and usefulness of the model is demonstrated by application to the Ln sulfides and the well-known Ln oxides LnO, Ln(2)O(3), and LnO(2) for which the model correctly predicts insulating, semiconducting, or metallic behavior, nature, and magnitude of band gap energies and chemical stability of Ln materials as well as valence and valence changes of Ln ions. The model may serve as a reliable tool to accelerate design of a broad range of Ln materials with deliberately chosen properties.