Large atomic disorder in nanostructured LaNi5 alloys: A La L3-edge extended X-ray absorption fine structure study

Local structure of the nanostructured LaNi5 alloys, prepared by ball-milling, has been studied using La L3-edge extended X-ray absorption fine structure spectroscopy. The near-neighbor distances tend to decrease with the ball-milling, and the mean square relative displacements (MSRD) show substantial increase suggesting an increased atomic disorder. High temperature annealing helps in partial recovery of atomic order in the ball-milled samples for milling times upto 20 h, however, the long-time ball-milled samples seems to gain only a local random order. The results suggest that reduced unit-cell volume together with large atomic-disorder might be causing a higher energy-barrier for the hydride-phase formation in the long time ball-milled LaNi5 powders.