The oxygen potential, Δ G ̄O2, of the solid solutions My3U1-yO2+x and My2+U1-yO2+x was analysed by calculating the number of ways of arranging the cationic defects as a function of x. The intra-cation complex (M3+ U5+) was assumed to be formed in My3+U1-yO2+x, while the presence of two kinds of complexes, i.e. (M2+U5+) and (M2+2U5+), was assumed in My2+U1-yO2+x with an average composition, (M2+αU5+). 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 My2+U1-yO2+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 My3+U1-yO2+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.
ASJC Scopus subject areas
- Nuclear and High Energy Physics
- Materials Science(all)
- Nuclear Energy and Engineering