Local and Electronic Structure of Americium‐Bearing PuO₂

Abstract

Abstract X‐ray diffraction and X‐ray absorption spectroscopy have shown that a material composed of two (Pu,Am)O 2– x substoichiometric fluorite‐type structures is obtained by sintering in moisturized Ar/H 2 . The Pu oxidation state is strictly +IV, whereas Am exhibits a +III/+IV mixed valence. Thus, the Am–O system and particularly the Am oxidation state play a major role in the sintering behavior of the Pu–Am–O system. The heating of this compound in air leads to the formation of a fluorite Pu 0.80 Am 0.20 O 1.98 solid solution. The transition from a one‐phase to a two‐phase structure takes place at a temperature lower than 800 °C. The results were compared with previous studies on Am‐bearing UO 2 and ThO 2 , which have evidenced different behaviors.