Local structure characterization of gadolinium doped amorphous and crystalline alumina

The evolution of local structure during the transition from amorphous to cr ystalline states of gadolinium doped alumina is characterized by electron p aramagnetic resonance (EPR). The EPR spectra of samples belonging to the (1 - x)Al(2)O(3)xGd(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 alpha -alumina appears on the surface of the gamma -alumina granules where there are low coordinated (N < 6) gadolinium species. The transition from gamma- to alpha -alumina is postponed by the presence of high coordinated gadolin ium (N < B) ions inside of gamma -alumina granules.