Oxygen potential measurements of Cm0.09Pu0.91O2−x by EMF method

Abstract

The dependence of the oxygen potentials on oxygen nonstoichiometry (x) and temperature of Cm0.09Pu0.91O2−x was measured by electromotive force (EMF) measurements. The galvanic cell type is shown: (Pt) air | Zr(Ca)O2−x | Cm0.09Pu0.91O2−x (Pt). The coulomb titration has been made for the sample at the intervals of 40 K between 1173 and 1333 K over the x range of 0.018 ≤ x ≤ 0.053. The oxygen potentials decreased gradually from −31.02 to −117.48 kJmol−1 with increasing x from 0.018 to 0.045, and more rapidly decreased from −117.48 to −283.74 kJmol−1 up to 0.053. The temperature dependence of the oxygen potentials was also measured between 1173 and 1333 K for several constant x values. The temperature dependences exhibited the smooth curves over the x and temperature ranges concerned. Systematic comparison of the oxygen potentials between Cm0.09Pu0.91O2−x and those published for CmO2 −x and Am-containing oxides was also made. The oxygen potential of Cm09Pu0.91O2−x at the equimolar ratio of Cm3+/Cm4+ was higher than those of AmyPu1−yO2−x at the equimolar ratio of Am3+/Am4+ by approximately 150 kJmol−1 when the Pu valence was assumed to be +4 in both oxides.