Synthesis and phase equilibria of Nd–Gd mixed oxycarbonates

Abstract

The synthesis of mixed Gd–Nd oxycarbonates was performed via a solid state route involving the decomposition of mixed oxalates. Depending on the reaction atmosphere, the compounds can form through two different reaction paths: by partial decomposition of the corresponding mixed oxalates or by complete decomposition of the oxalates followed by partial carbonation. All the oxycarbonates, when prepared at 600 °C in static air or CO 2, form a solid solution, crystallize in the hexagonal structure and follow Vegard's law. If treated at lower temperature, Nd oxalate gives rise to the monoclinic structure, so that the monoclinic → hexagonal phase transition can be observed. The decomposition of the oxycarbonates leads to the cubic form of the corresponding oxide for each composition.