Fluoride-Conversion Synthesis of Homogeneous Actinide Oxide Solid Solutions

Abstract

The synthesis of (U,Th)O(2) solid solutions at a relatively low temperature of 1100 °C using a new technique is described. First, separate actinide oxides were reacted with ammonium hydrogen fluoride to form ammonium actinide fluorides at room temperature. Subsequently, this fluoride was converted to an actinide oxide solid solution using a two-phase reaction process, which involved heating of the fluoride first at 610 °C in static air followed by heating at 1100 °C in flowing argon. Oxide solid solutions of UO(2) and ThO(2) were synthesized for a ThO(2) content from 10 to 90 wt %. Microscopic investigation showed that the (U,Th)O(2) solid solutions synthesized using this method had high crystallinity and homogeneity up to nanoscale.

From Coordination Polymers to Doped Rare‐Earth Oxides

“…[8] In order to avoid mechanical grinding and high calcination temperatures, a novel technique by fluoride conversion was also recently proposed for synthesis of mixed thorium-uranium oxides. [9] The solution route has been useful for synthesising mixed oxides such as gadolinium-doped ceria. [10] It offers the advantage of a good control of the stoichiometry and purity, a high-yield synthesis and a regular and controlled morphology of the end-products.…”

“…Usual methods to synthesise f‐element mixed oxides include mechanical mixing of two monometallic oxide powders, co‐precipitation with oxalates,5 hydroxides,6 acetates or carbonates,7 and various sol–gel techniques 8. In order to avoid mechanical grinding and high calcination temperatures, a novel technique by fluoride conversion was also recently proposed for synthesis of mixed thorium–uranium oxides 9. The solution route has been useful for synthesising mixed oxides such as gadolinium‐doped ceria 10.…”