Oxygen potential measurements of fluorite-type Zr 0.5Pu 0.5O 2− y by EMF method

Abstract

The dependence of the oxygen potentials ( g(O 2)) on oxygen non-stoichiometry ( y) and temperature ( T) of oxygen-deficient fluorite-type (F-type) plutonium zirconate Zr 0.5Pu 0.5O 2− y has been elucidated by electromotive force (EMF) measurements: (Pt) air ∣Zr(Ca)O 2− x ∣ Zr 0.5Pu 0.5O 2− y (Pt). The y value of Zr 0.5Pu 0.5O 2− y was varied at 1078 K over 0 ⩽ y < 0.10 and the isothermal g(O 2) were measured by applying the coulomb titration method. The temperature dependence of the g(O 2) was also measured for each y by performing the temperature scan down to 793 K (793 ⩽ T ⩽ 1078 K). It was found that the g(O 2) decreased from ∼0 to −480 kJ/mol with increasing y from ∼0 to 0.1 at 1078 K and that the isothermal g(O 2) as a function of y exhibited a simple concave curve. The powder XRD results showed that Zr 0.5Pu 0.5O 2− y maintained its single F-type structure over 0 ⩽ y < 0.10 at 1078 K. The lattice parameters ( a 0) in this system were found to increase almost linearly with y over 0 ⩽ y < 0.10.