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Computer simulation techniques have been used to model cubic CeO2−ZrO2 solid solutions in the whole composition range. Aspects related with the oxygen storage capacity of these materials are emphasized. The energetics of the Ce4+/Ce3+ bulk reduction reaction as well as the activation energy for oxygen migration in the lattice are investigated and compared with the corresponding quantities in pure CeO2. It is found that even small additions of ZrO2 decrease the bulk reduction energy of Ce4+ to values comparable to those reported for surface reduction in pure CeO2. Activation energy calculations indicate an almost monotonic increase of oxygen mobility with increasing zirconia content.

The (110), (111), and (310) surfaces of cubic CeO 2 -ZrO 2 solid solutions have been studied by computer simulation techniques using atomistic models. Surface energies, Ce 4+ /Ce 3+ reduction energies, and penetration profiles of oxygen vacancy formation have been calculated. The results of the calculations suggest some possible factors that could explain the increase in the oxygen storage capacity experimentally observed in these systems relative to pure ceria: surface Ce 4+ /Ce 3+ reduction energies are comparable with previously found bulk values; introduction of zirconia into the ceria lattice decreases the Ce 4+ /Ce 3+ reduction energy on the stable (110) and (111) surfaces; oxygen vacancies tend to segregate to these surfaces.

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Cubic solid solutions of general formula Ce1 - xMxO2 (M = Zr, Th, Hf) have been modeled in the range (0 < x < 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.