After a short review on the existing regions and thermodynamic properties of essentially ionic ternary uranium dioxide solid solutions, MyU1-yO2+x (x ≧< 0), classified by the valency of the M metals, a description is made for our study on the solubility and the crystal chemistry of Mg in the Mg solid solution in a range of low po2. The single phase region extended up to at least y = 0.1 at 1200°C in po = 10-15 or ≤ 10-19 atm. Density measurements revealed that the Mg atoms in the solid solution formed under the above conditions are about 60% in the interstitial sites. This experimental result was rationalized by the calculated ΔḠO2 change caused from the configurational partial molar entropy obtained through the lattice statistics of the occupation of Mg and oxygen atoms in the solid solution lattice sites.
ASJC Scopus subject areas