Sorption properties and temperature-dependent near-surface chemistry of the BaLi4 intermetallic compound

BaLi4 alloy has been analyzed using x-ray photoelectron spectroscopy and Ar+ ion depth profiling. A series of gases sorption tests have also been performed. The effects induced by room temperature (RT) gas exposure (air, N-2, and O-2) and vacuum annealing at low temperature (approximate to 100 degrees C) have been studied in detail. High sorption capabilities are confirmed compared with previous works. Dosing the BaLi4 with N-2 does not lead to appreciable change in the nitrogen surface concentration, However, its apparent concentration increases after repeated Ar+ sputtering, demonstrating the existence of a chemical reaction with the bulk alloy. This is shown to be in good agreement with N-2 sorption tests carried out at RT on BaLi4 powder. (C) 1999 American Vacuum Society. [S0734-2101(99)08805-3].