### Abstract

The oxygen potential, Δ G ̄_{O2}, of the solid solutions M_{y}^{3}U_{1-y}O_{2+x} and M_{y}^{2+}U_{1-y}O_{2+x} was analysed by calculating the number of ways of arranging the cationic defects as a function of x. The intra-cation complex (M^{3+} U^{5+}) was assumed to be formed in M_{y}^{3+}U_{1-y}O_{2+x}, while the presence of two kinds of complexes, i.e. (M^{2+}U^{5+}) and (M^{2+}2U^{5+}), was assumed in M_{y}^{2+}U_{1-y}O_{2+x} with an average composition, (M^{2+}αU^{5+}). According to the experimental results reported, the x values at which the steepest change in Δ G ̄_{O2} takes place seem to be in the range of x < 0 for M_{y}^{2+}U_{1-y}O_{2+x}, which was seen to be well explained by the present model as x = -(1 - α/2)y with α < 2 by calculating the number of ways of the arrangement of the above complexes. The model also makes it possible to explain the fact that the x value for the steepest change of Δ G ̄_{O2} is zero for M_{y}^{3+}U_{1-y}O_{2+x}. By introducing a factor β (0 < β < 1), which is multiplied to the logarithmic term in Δ S ̄_{O2}, the oxygen potentials of the exemplified La, Mg and Eu solid solutions were found to be represented satisfactorily by the respective theoretical curves in a wide range of the x values. Calculations revealed that nearly x-independent Δ H ̄_{O2} values, as expected, could be obtained by using β.

Original language | English |
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Pages (from-to) | 103-115 |

Number of pages | 13 |

Journal | Journal of Nuclear Materials |

Volume | 189 |

Issue number | 1 |

DOIs | |

Publication status | Published - 1992 Jul 1 |

### ASJC Scopus subject areas

- Nuclear and High Energy Physics
- Materials Science(all)
- Nuclear Energy and Engineering