Luminescence studies of lanthanide oxides. I. Thermal and hydration effects on the metal ion site symmetry in europium oxide catalysts

High-resolution luminescence spectroscopy has been used to study the site symmetry of Eu(III) ions in Eu2O3 prepared under conditions suitable for catalytic use. It was found that the Eu(III) site symmetry was a sensitive function of the pretreatment procedure, and it proved possible to determine the number of spectroscopically nonequivalent Eu(III) ions in the oxide material from an analysis of the fine structure within the emission bands. The site symmetry is altered primarily by thermal effects, and hydration of the oxide is not found to induce large changes in site symmetry