Oxygen potential measurements of Am0.5Pu0.5O2−x by EMF method

The dependence of the oxygen potentials on oxygen non-stoichiometry and temperature of Am0.5Pu0.5O2−x has been obtained by the electromotive force (EMF) method with the cell: (Pt) air |Zr(Ca)O2−x| Am0.5Pu0.5O2−x (Pt). The x value of Am0.5Pu0.5O2−x was changed at 1333 K over 0.02 < x ⩽ 0.25 by the coulomb titration method. The temperature dependence of the oxygen potential was also measured over the range of 1173–1333 K. It was found that the oxygen potential decreased from −80 to −360 kJ mol−1 with increasing x from 0.021 to 0.22 at 1333 K and that it remained almost constant at −360 kJmol−1 around x = 0.23. It was concluded that Am0.5Pu0.5O2−x should be composed of the single fluorite-type phase over 0.02 < x ⩽ 0.22 and the mixed phases of fluorite-type and (Am, Pu)9O16 at around x = 0.23.