Bulk reduction and oxygen migration in the ceria-based oxides

Cubic solid solutions of general formula Ce(1-x)M(x)O2 (M = Zr, Th, Hf) have been modeled in the range (0 < χ < 1) using atomistic simulation methods. The Ce4+/Ce3+ reduction energy in the bulk materials and the activation energy for oxygen migration have been calculated. The Ce4+/Ce3+ reduction energy decreases with increasing M content for M = Zr, Th, the most remarkable effect being displayed for M = Th. An opposite trend is obtained when M = Hf. The activation energy for oxygen migration decreases with increasing M content. The effect of Th is similar to that of Zr and consists of a substantial decrease of the activation energy at high concentrations. On the other hand, the activation energy decreases only slightly when M = Hf.