Eu3 + as a luminescent probe for the local structure of trivalent dopant ions in barium zirconate-based proton conductors

The luminescence spectra and decay kinetics of dry and hydrated samples of BaZr0.9Y0.099Eu0.001O2.95 have been measured at room temperature. The spectra of the dry sample evidence two 5D0 → 7F0 bands clearly indicating that Eu3 + (replacing Y3 + in the Zr4 + position of the average cubic perovskite structure) occupies two different local structures, whilst only one Eu3 + site is observed for the hydrated material. From the spectral data, it is possible to identify the nature of these two sites and to propose point group symmetries for the average local geometry around Eu3 +. The decay time of the 5D0 level becomes shorter upon hydration, due to the interaction with high-frequency O–H stretching vibrations, indicating an attractive interaction between protons and dopant atoms.