Dennis de D Graaf

Long wavelength Eu2+ emission in Eu-doped Y–Si–Al–O–N glasses

Abstract A number of (Eu,Y)–Si–Al–O–N glasses have been prepared and their optical properties examined. Eu was found to be present in the divalent instead of in the trivalent state due to a reaction between the Eu 3+ and the chemically incorporated N 3- during the preparation of the glasses. The luminescence characteristics were found to be negligibly influenced by the O/N and Si/Al ratio, but appear to be strongly dependent on the concentration and type of modifying cations (Eu,Y). As a function of the cationic composition the emission shifts from wavelengths below 500 nm to wavelengths as long as 640 nm, which is very unusual for Eu 2+ containing compounds. This shift to longer wavelengths is ascribed to a combination of energy transfer between the different sites and change of the Eu 2+ site distribution.

Reduction of Lanthanide Ions in Si-Al-O-N Glasses

The goal of this study is to determine the oxidation state of ytterbium and samarium in oxynitride glasses. After evaluation of the optical and mechanical properties of the glasses it can be concluded that both ions partially reduce from the trivalent state in the raw materials to the divalent state in the glasses. The resulting glasses thus contain a mixture of the divalent and trivalent ion.