LOCAL STRUCTURE CHARACTERIZATION OF GADOLINIUM DOPED AMORPHOUS AND CRYSTALLINE ALUMINA

The evolution of local structure during the transition from amorphous to crystalline states of gadolinium doped alumina is characterized by electron paramagnetic resonance (EPR). The EPR spectra of samples belonging to the (1 - x) Al 2 O 3 x Gd 2 O 3 system, where x = 0.002, 0.01, 0.05 and 0.1, show that the gadolinium ions are relatively uniformly distributed in amorphous alumina granules prepared by sol–gel methods. First, gadolinium doped α-alumina appears on the surface of the γ-alumina granules where there are low coordinated (N < 6) gadolinium species. The transition from γ- to α-alumina is postponed by the presence of high coordinated gadolinium (N < 6) ions inside of γ-alumina granules.