The growth and evolution of thin oxide films on δ-plutonium surfaces

Authors

Harry G. García Flores, University of Nebraska - Lincoln
David L. Pugmire, University of Nebraska-LincolnFollow

Date of this Version

2010

Comments

Published in Materials Science and Engineering 9, 1-7 (2010). Copyright © 2010 IOP Publishing Ltd. Used by Permission.

Abstract

The common oxides of plutonium are the dioxide (PuO₂) and the sesquioxide (Pu₂O₃). The nature of an oxide on plutonium metal under air at room temperature is typically described as a thick PuO₂ film at the gas-oxide interface with a thinner Pu₂O₃ film near the oxide-metal substrate interface. In a reducing environment, such as ultra high vacuum, the dioxide (Pu⁴⁺; O/Pu=2.0) readily converts to the sesquioxide (Pu³⁺; O/Pu=1.5) with time. In this work, the growth and evolution of thin plutonium oxide films is studied with x-ray photoelectron spectroscopy (XPS) under varying conditions. The results indicate that, like the dioxide, the sesquioxide is not stable on a clean metal substrate under reducing conditions, resulting in substoichiometric films (Pu₂O_3-y). The Pu₂O₃-y films prepared exhibit a variety of stoichiometries (y~0.2-1) as a function of preparation conditions, highlighting the fact that caution must be exercised when studying plutonium oxide surfaces under these conditions and interpreting resulting data.