Oxygen migration energy in La and Y Co-doped CeO2: Effect of lattice constant and grain boundary segregation

초록

The transfer energy of oxygen vacancy of La and Y co-doped CeO2 is investigated in which the total amount of La and Y is fixed at 20 at%. Although both the La3+ (1.16 angstrom) and Y3+ (1.032 angstrom) ions are larger than the CO4+ ions (0.97 angstrom), individual single doping of La and Y results in an increase and decrease in the CeO2 lattice constant, respectively, due to the effect of the critical ionic radius (r(c)). As the La/Y ratio varies, the lattice constant increases as the La content increases, which leads to a decrease in the migration energy of the oxygen vacancy in the grain interior. When La and Y are co-doped at a ratio of 2:18, its lattice constant is almost the same as that of pure CeO2 in which the dissociation energy of the oxygen vacancy achieves the lowest value due to the minimum lattice-strain energy. The migration energy at the grain boundary also decreases with increasing La content. This result is explained by the degree of grain boundary segregation of the dopant. (C) 2022 Vietnam National University, Hanoi. Published by Elsevier B.V.

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