Surface and subsurface properties of a BaLi4 gettering alloy studied using x-ray photoemission spectroscopy

A barium-lithium alloy in a 1:4 atomic ratio is analysed using XPS and Ar+-ion depth profiling. The effects induced by RT gas exposure (air, N-2 and O-2) and vacuum annealing at low temperature (100 degrees C) are studied in detail. A strong reactivity of the alloy surface is found, even at RT. Dosing BaLi4 with N-2 does not lead to an appreciable change in the nitrogen surface concentration. However, its 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) 1998 Elsevier Science B.V. All rights reserved.