Synthesis, EXAFS investigation and optical spectroscopy of nanocrystalline Gd3Ga5O12 doped with Ln3+ ions (Ln = Eu, Pr)

Gadolinium Gallium Garnet (GGG) nanocrystalline powders doped with Eu3+ and Pr3+ ions have been obtained using three different methods (combustion, coprecipitation and Pechini). Their luminescence spectroscopy and the EXAFS spectroscopy at the Pr-edge have been investigated in detail, in particular in order to identify the classes of sites occupied by the dopant ions. In the case of GGG:Eu3+, luminescence spectra show the presence of several bands due to the presence of lanthanide ions in non regular sites and to distortion of the local geometry. Various relaxation mechanisms of the excited levels are present in the differently prepared samples doped with Pr3+. EXAFS spectroscopy of GGG:Pr3+ shows the presence of significant static disorder in the next nearest neighbours in the sample prepared by the combustion synthesis, in comparison with the bulk material. The Pechini method seems to produce the best GGG:Ln3+ nanocrystalline samples.