Nb clusters formation in Nb-doped magnesium hydride

Extended x-ray absorption fine structure spectroscopy, x-ray diffraction and transmission electron microscopy were used to analyze the Nb coordination and clustering in Nb-doped (5 at. %) h-Mg film samples deposited by rf magnetron sputtering. Results show that the catalytic effect of the Nb doping in the H-2 absorption and desorption kinetics is connected with the formation of Nb nanoclusters dispersed in the host matrix. The H-2 desorption from beta-MgH2 is favored by local elastic stresses produced by beta-NbH0.89 clusters on the MgH2 matrix that reduces the stability of the hydride phase and by preferential paths in the nanocomposite hydride. (c) 2005 American Institute of Physics.