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

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 ofin the trivalent state due to a reaction between the Eu³⁺ and the chemically incorporated N^3- during the preparation ofthe 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 Eu²⁺ containing compounds. This shift to longer wavelengths is ascribed to a combination of energy transfer between the different sites and change ofthe Eu2+ site distribution.