The effect of different gas atmospheres such as H-2(g), synthetic air, carbon monoxide (CO) and nitrogen (N-2) on the Eu3+ -> Eu2+ reduction process during the synthesis of Eu-doped BaAl2O4 was studied using synchrotron radiation. The Eu3+ -> Eu2+ reduction was monitored analyzing XANES region when the sample are excited at the Eu L-III-edge. The results show that the hydrogen reducing agent are the most appropriate gas for Eu2+ stabilization in BaAl2O4 and that only a part of the Eu ions can be stabilized in the divalent state. A model of Eu reduction process, based on the incorporation of charge compensation defects, is proposed. (C) 2014 Elsevier Ltd. All rights reserved.