Phase stability of yttria-stabilized zirconia with dissolved cerium and neptunium oxides under oxidizing and reducing atmospheres

Phase stability and effects of sintering atmosphere on the crystalline stru cture of Np-doped yttria-stabilized zirconia (YSZ) were evaluated in compar ison with those same properties and conditions for Ce-doped YSZ. Different sintering atmospheres for Ce-doped YSZ led to differences in phase formatio n through reduction of the dopant from Ce4+ to Ce3+ On the other hand, YSZ specimens containing up to 40 mol% Np formed only a fluorite-structure phas e regardless of sintering atmosphere. Yttria-stabilized zirconia thus seems to accommodate Np within a wide range of concentrations and to have excell ent phase stability under both oxidizing and reducing atmospheres.